2025-1 NFS284 Essay Page 1 of 29



2025-1-NFS284: Essay (20% of final grade) Due Date: Online Mar 2 at 11:59PM
This assignment requires you to write a short essay (500 words) on the research question given
below. To complete this assignment effectively you need to do the following:
a) Complete the Science Writing Quiz Online: Due date: Feb 16 at 11:59 PM.
b) Read this handout carefully and completely. Review the information on nutritional research,
both described in the handout below (Appendix 2) and from the face-to-face lecture, especially
the strengths and limitations of intervention trials and observational studies and how to
interpret the results of statistical analysis.
c) Note: Writing Centres can help students improve the organization, grammar and style of an
essay: http://www.writing.utoronto.ca/writing-centres. You may wish to schedule an
appointment with your college’s Writing Centre instructor for feedback and advice as you work
on your essay. Be sure to book early!

Due Date: Mar 2 at 11:59PM ( ONLINE submission only). To facilitate the determination of word
counts the essay must be submitted as a Word document: doc; docx. Quercus will block your
submission if the file format is incorrect. On Quercus, online submissions will automatically be
submitted to Turnitin, but you will have to agree to the Turnitin license agreement. See the course
syllabus for more information on Turnitin as a plagiarism prevention tool and alternatives.
ASSIGNMENT INSTRUCTIONS:
Write a short (500 words) essay that answers the following question:

Based on the studies described in Appendix 1, how convincing is the scientific evidence
that the DASH diet decreases the risk of death from cardiovascular disease?

IMPORTANT: There is no “right” answer to this question. Interpretations, of how convincing the
evidence is, can vary e.g. very convincing, somewhat convincing, not very convincing. What is
important is to demonstrate, in making your assessment of the evidence, that you understand the
strengths and limitations of the scientific studies presented, can appropriately interpret the studies’
results, and provide a reasonable defense of your position.
To complete the assignment
• You need only use the information found in the abstracts in Appendix 1 (the abstracts - an
abstract is a short summary of a scientific study), Appendix 2 and the lecture material on
nutritional research. You are NOT required or expected to use any additional sources.
• You must, however, include a discussion of ALL abstracts, found in Appendix 1, in your essay.
• Your essay should include a brief introductory paragraph (2-3 sentences), a body (typically
consisting of several short paragraphs) and a conclusion (2-3 sentences).
• You are expected to paraphrase your sources (i.e. the abstracts) properly, and include in-text
citations and a bibliography, as described in the document: SCIENCE_WRITING_ Notes that is
posted with the Science Writing Quiz and the How to cite references document.
• Information that you might use to support your argument that comes from the Appendix 2 or
the lecture material on nutritional research can be considered common knowledge and does
not require citation.
• For writing tips and information on how the assignment will be graded read Appendix 3 - 5.
• For info on bibliographic referencing see Appendix 4. Be sure to follow the format correctly. It is
slightly different from the format used in the abstracts in Appendix 1.
Word limit: 500 (INCLUDING in-text citations, but excluding the bibliography).
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s

Getting Organized:

There is a lot of information in this handout. As shown in the graphic below, it is divided into several
appendices, to help you successfully organize and complete your assignment. Other sources of useful
information is also listed.


Questions about the assignment:
If you have questions about the assignment you can post them on the course discussion board (a special forum has
been set up for assignment questions) or visit Dr. Laar during office hours, Tuesday 1-3pm @ MS 5267 OR book-a-
time for a virtual meeting @ https://calendly.com/matilda-laar/book-a-time-nfs284-virtual-office-hours. Questions
posted on the course discussion board up to Feb 28 at 9 AM will be answered. It will not be possible to answer
questions posted after that time. If these dates and times prove unsuitable for you, e-mail Dr Laar for an alternate
appointment.
refer to
To write your essay:
Science Writing Quiz Due Feb 16-online at 11:59PM
APPENDIX 1: Abstracts
APPENDIX 2: Research Study Design & the Interpretation of
Results
APPENDIX 3: Tips for writing your essay
APPENDIX 4: How to format references
APPENDIX 5: How this assignment is graded (including

Additional information on nutritional research from face-to-
face lectures.
refer to
APPENDIX 6: What to hand in: ONLINE
APPENDIX 7: Late submission policy
To prepare your
essay for
submission:
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Appendix 1:
Use the abstracts provided below to write your essay. All of these abstracts are obtained from the
PubMed database and should be cited as PubMed abstracts. See Appendix 3 on how to format in-text
citations and a bibliography, which is different from the formatting used in the abstracts below.
Please note that, for the purposes of this assignment and for clarity, modifications and additions have
been made to the original content of these abstracts. For example, abstracts do not typically contain
tables, but they are included here to help you learn how to interpret data. This assignment deals with
cardiovascular disease (CVD). The description below will assist you with the terminology that you will
encounter in the abstracts and help you to understand some of the risk factors for cardiovascular
disease that are described in the abstracts.
Definition of cardiovascular disease, coronary heart disease, and stroke.
The slide below illustrates the definition of CVD, which effects various parts of the body, by blocking
blood vessels due to the development of atherosclerosis (see left). When these blockages take place
in the heart, the terms coronary heart disease
(CHD), ischemic heart disease (IHD) and/or
coronary artery disease (CAD) are used to describe
a variety of conditions of the heart, that develop
as a result of these blockages. The most common
of these conditions is heart attack, which is also
referred to as myocardial infarction. When the
blockage of the blood vessel occurs in the brain,
stroke occurs. Cardiovascular disease refers to
disease affecting both the heart and the brain.


Risk factors of CVD.


Atherosclerosis: Most CVD has its origin in the
development of atherosclerosis, shown left. A
low-density lipoprotein (LDL)(red arrow), a
particle high in cholesterol and also containing
triglycerides and protein, that normally
circulates in the blood, moves from the blood
into the walls of the blood vessels and sets off a
series of reactions that include the formation
of fatty streaks (shown left). These fatty
streaks eventually form plaques that can block
the blood vessel or promote the formation of
blood clots that can also block blood vessels.
These blockages, if they occur in the arteries of
the heart or brain can result in heart attack or
stroke.



Lipoproteins and blood lipids: As noted above, a lipoprotein called the low-density lipoprotein, rich in
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cholesterol, plays a role in the development of CVD. The amount of cholesterol found in these particles
(shown left) is measured and LDL-cholesterol is often referred to as “bad” cholesterol, because of its link to
atherosclerosis.


A second important particle is the high-density lipoprotein (HDL). HDLs
function to remove cholesterol from the blood, and so HDL-cholesterol, i.e.
cholesterol in the HDL particle, is often referred to as “good” cholesterol,
because it does not contribute to disease. In addition to LDL and HDL, there
are other lipoproteins that circulate in the blood. These lipoproteins contain
both cholesterol and triglycerides and so total cholesterol and total
triglycerides are often measured in the blood, as these blood lipids are
associated with cardiovascular disease risk. Studies have also shown that the
ratio of total cholesterol to HDL-C (i.e. TC/HDL-C) is also a good predictor of
CVD risk. The relationship between blood lipids, which are described in the
abstracts, and disease risk is shown in the table below:

CVD risk increases with increases in:
• LDL-cholesterol
• Total cholesterol
• TC/HDL-C
CVD risk decreases with increases in:
• HDL cholesterol

Other risk factors for CVD: In addition to blood lipids, other risk factors for CVD exist:
Blood pressure: Blood pressure is measured as two numbers: systolic pressure (pressure when the heart
contracts) and diastolic pressure (pressure when the heart relaxes), using the units mmHg; for example normal
pressure is 120/80 reported verbally as “120 over 80.” The table below shows typical blood pressure
measurements and how they are interpreted. Increases in blood pressure are associated with increases in
CVD.



In this assignment you will be reading about the relationship between cardiovascular disease and the DASH
diet.

The DASH eating plan was developed to reduce blood pressure. Its composition is shown below:
DASH diet
• High in vegetables, fruit, low-fat fermented dairy products, whole grains, poultry,
fish, and nuts
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• Low in sweets, sugar-sweetened beverages, and red meats
• Low in saturated fat, total fat, and cholesterol
• Rich in potassium, magnesium, and calcium
• Rich in protein and fibre
Source: Ravera A, Carubelli V, Sciatti E, Bonadei I, Gorga E, Cani D,Vizzardi E, Metra M,
Lombardi C. Nutrition and Cardiovascular Disease: Finding the Perfect Recipe for
Cardiovascular Health. Nutrients. 2016 Jun 14;8(6). pii: E363. doi: 10.3390/nu8060363



Below are the four abstracts that are required for this essay:

1. Appel LJ, Moore TJ, Obarzanek E, Vollmer WM, Svetkey LP, Sacks FM, Bray GA, Vogt TM, Cutler JA,
Windhauser MM, Lin PH, Karanja N.
A clinical trial of the effects of dietary patterns on blood pressure. DASH Collaborative Research Group.
N Engl J Med. 1997 Apr 17;336(16):1117-24. DOI: 10.1056/NEJM199704173361601

BACKGROUND: It is known that obesity, sodium intake, and alcohol consumption factors influence blood
pressure. In this clinical trial, Dietary Approaches to Stop Hypertension (DASH), we assessed the effects of
dietary patterns on blood pressure.

METHODS: We enrolled 459 healthy adults (49.9% female; 50.1% male; 60% African American), > 22 years,
from four U.S. cities, with systolic blood pressures of less than 160 mm Hg and diastolic blood pressures of 80
to 95 mm Hg. For three weeks, the subjects were fed a control diet that was low in fruits, vegetables, and dairy
products, with a fat content typical of the average diet in the United States. They were then randomly assigned
to receive for eight weeks the control diet, a diet rich in fruits and vegetables (F-V diet), or a "combination"
diet rich in fruits, vegetables, and low-fat dairy products and with reduced saturated and total fat, (DASH diet).
Sodium intake and body weight were maintained at constant levels. All food was prepared in research kitchens
and provided to participants. Dinner and supper were consumed at the workplace and other meals, including
weekend meals, were packed in coolers for home use.

RESULTS: The results below compare the change in either systolic or diastolic pressure from the beginning to
the end of each of the two treatments to the change as a result of the control diet and a comparison of the
two treatments. The P-value indicates whether there is a statistically significant difference between the two
groups being compared. A negative result, e.g. -5.5 mm Hg indicates a decrease in blood pressure, as a result
of the intervention.

SYSTOLIC
PRESSURE
Change in DASH group
minus Change in control
group
Change in DASH diet
minus Change in F-V diet
group
Change in F-V diet group
minus Change in control
group
mm Hg P-value mm Hg P-value mm Hg P-value
All subjects -5.5

<0.001 -2.7

0.001 -2.8 <0.001
Non-
hypertensive
-3.5

<0.001 -2.7 0.001 -0.8 <0.33
Hypertensive -11.4 <0.001 -4.1 0.04 -7.2 ,0.001
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DIASTOLIC
PRESSURE
Change in DASH group
minus Change in control
group
Change in DASH diet
minus Change in F-V diet
group
Change in F-V diet group
minus Change in control
group
mm Hg P-value mm Hg P-value mm Hg P-value
All subjects -3.0

<0.001 -1.9

0.002 -1.1 <0.001
Non-
hypertensive
-2.1

<0.003 -1.8 0.009 -0.3 <0.33
Hypertensive -5.5 <0.001 -2.6 0.03 -2.8 ,0.001


2. Azadbakht L, Fard NR, Karimi M, Baghaei MH, Surkan PJ, Rahimi M, Esmaillzadeh A, Willett WC.
Effects of the Dietary Approaches to Stop Hypertension (DASH) eating plan on cardiovascular risks among
type 2 diabetic patients: a randomized crossover clinical trial.
Diabetes Care. 2011 Jan;34(1):55-7. doi: 10.2337/dc10-0676.

OBJECTIVE: To determine the effects of the Dietary Approaches to Stop Hypertension (DASH) eating pattern on
cardiometabolic risks in type 2 diabetic patients.

RESEARCH DESIGN AND METHODS: A randomized crossover clinical trial was undertaken in 31 type 2 diabetic
patients, 13 males, in a major urban center in Iran. For 8 weeks, participants were randomly assigned to a
control diet or the DASH eating pattern. Participants crossover for a second 8-week period, after a 4-week
wash-out. Participants were counseled on what foods to eat. The control diet was a based on the typical
Iranian diet with recommendations suitable for the management of type-2-diabetes. Its macronutrient
composition was 50-60% kcal carbohydrates, 15-20% kcal protein, less than 30% kcal total fat and less from 5%
kcal from sugar. The DASH diet was rich in fruits, vegetables, whole grains, and low-fat dairy products and low
in saturated fat, total fat, cholesterol, refined grains and sweets.

RESULTS: The results, comparing the control to the DASH diets, are shown below. The P-value indicates
whether there is a statistically significant difference between control and DASH diet.

Control Diet DASH diet P-value
Systolic blood pressure (mm Hg) -3.1 +/- 2.7 -13.6 +/- 3.5 0.02
Diastolic blood pressure (mm Hg) -0.7 +/- 3.3 -9.5 +/- 2.6 0.04
Fasting blood glucose (mg/dL) -12.8 +/- 6.7 -29.4 +/- 6.3 0.04
HDL-cholesterol (mg/dL) 1.3 +/- 0.7 4.3 +/- 0.9 0.001
LDL-cholesterol (mg/dL) -2.7 +/- 4.8 -17.2 +/- 3.5 0.02
Total cholesterol (mg/dL) -8.3 +/- 6.3 -22.1 +/- 5.7 0.11


3. Reedy J, Krebs-Smith SM, Miller PE, Liese AD, Kahle LL, Park Y, Subar AF.
Higher diet quality is associated with decreased risk of all-cause, cardiovascular disease, and cancer
mortality among older adults.
J Nutr. 2014 Jun;144(6):881-9. doi: 10.3945/jn.113.189407.
2025-1 NFS284 Essay Page 7 of 29




Increased attention in dietary research and guidance has been focused on dietary patterns, rather than on
single nutrients or food groups, because dietary components are consumed in combination and correlated
with one another. We examined the relationships between several dietary patterns and disease outcomes,
including Dietary Approaches to Stop Hypertension (DASH)--and cardiovascular disease (CVD) mortality.

Participants were from the NIH-AARP Diet and Health Study (n = 492,823). They were between the ages
of 50 and 71 years, with no history of cardiovascular disease or cancer, and from 6 American states (California,
Florida, Louisiana, New Jersey, North Carolina, and Pennsylvania). Data from a validated food-frequency
questionnaire, conducted only once, at the start of the study, were used to determine a DASH score and the
study has a 15-year follow-up. The scoring system gave points for the consumption of food from the DASH
plan e.g. whole grains, vegetables (excluding potatoes), fruit, nuts, legumes, fish, and also gave points for low
intakes of red and processed meat. The higher the score the better the adherence to the DASH dietary pattern.

The results for the DASH and CVD mortality are shown below and were adjusted for the following
confounding factors:
Men: age, race/ethnicity, education, martial status, physical activity, smoking, energy intake, BMI, diabetes,
alcohol
Women: All factors listed above for men + hormone replacement therapy

Quintile Men* Women*
HR (95% confidence interval) HR (95% confidence interval)
1-lowest score 1 1
2 0.95 (0.90 to 1.01) 0.88 (0.82 to 0.95)
3 0.91 (0.86 to 0.95) 0.84 (0.79 to 0.89)
4 0.88 (0.84 to 0.92) 0.80 (0.74 to 0.86)
5-highest score 0.86 (0.81 to 0.91) 0.78 (0.72 to 0.83)
*P-trends were not reported

4. Talaei M, Koh WP, Yuan JM, van Dam RM.
DASH Dietary Pattern, Mediation by Mineral Intakes, and the Risk of Coronary Artery Disease and Stroke
Mortality.
J Am Heart Assoc. 2019 Mar 5;8(5):e011054. doi: 10.1161/JAHA.118.011054.

Background The association of the Dietary Approaches to Stop Hypertension (DASH) dietary pattern with
stroke and coronary artery disease ( CAD) mortality has not been evaluated in Asian populations.

Methods Data from 57,078 participants (35,303 women) of the Singapore Chinese Health Study was used.
Participants were aged 45 to 74 years at baseline (1993-1998), with no history of cardiovascular disease or
cancer. Information on usual diet was collected by a validated 165-item food frequency questionnaire at
recruitment (beginning of study) only, and mortality information was obtained via the nationwide death
registry to December 31, 2014 for an average follow-up of 17.4 years. We constructed DASH scores based on
the intake of whole grains, vegetables (excluding potatoes), fruit, nuts, legumes, fish, and low intakes of red
and processed meat. The higher the score, the higher the quality of the DASH diet.

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Results: Cox proportional hazard models (a statistical analysis) were used to calculate hazard ratios and
corresponding 95% confidence intervals (CI). Hazard ratios were adjusted for age, sex, year of recruitment,
education, BMI, physical activity, smoking status, alcohol use, energy intake, dietary supplement use, history of
diabetes, history of hypertension.

Dash scores-
Quintiles:
CVD mortality
HR (95% CI)
CAD mortality
HR (95% CI)
Stroke mortality
HR (95% CI)
1-lowest score 1.00 1.00 1.00
2 0.89 (0.81-0.98) 0.90 (0.80-1.02) 0.86 (0.73-1.02)
3 0.82 (0.74-0.90) 0.81 (0.71-0.92) 0.79 (0.66-0.94)
4 0.78 (0.71-0.87) 0.78 (0.68-0.89) 0.74 (0.62-0.88)
5-highest score 0.70 (0.64-0.78) 0.69 (0.69-0.80) 0.64 (0.53-0.78)
P for trend <0.001 <0.001 <0.001



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Appendix 2: Research Study Design and the Interpretation of Results
This appendix provides background material required to complete your essay assignment. It will
describe the purpose of the assignment, important concepts in nutritional research study design, and
the interpretation of study results and statistical analysis that you will need to know, to complete the
assignment. There is a high degree of overlap between this Appendix and the face-to-face lecture on
nutrition research.
Purpose of the Assignment
The purpose of this essay is to simulate, in a much shorter and more simplified manner, the process of
reviewing the scientific literature on an important topic in nutrition and making an assessment of the
scientific literature. This assessment is the content of your essay.
The four steps in a literature review are listed below:
❶Formulate a research question.
❷Search the literature for relevant studies that address this question.
❸Critically evaluate each of the studies.
➍After looking at the individual studies, consider the totality of the scientific evidence and
formulate an answer to the research question.
As part of the “simulation” of a literature review, some of the steps in the process have been done for
you. For example, a research question been formulated for you to work on:
Based the studies described in Appendix 1, how convincing is the scientific evidence that the DASH
diet increases the risk of cardiovascular disease?
The next step in the process has also been done for you. The literature has been searched and abstracts
from four articles have been made available in appendix 1 of this assignment handout. For the purposes
of this assignment the information in these abstracts represents all the scientific evidence needed to
assess the relationship between DASH diet and cardiovascular disease (CVD).
Note that you are not required or expected to use any additional sources. This is intentional so that you
can focus your time on the analysis and interpretation of the information that you have been given. For
a real literature search, rather than this simulation, you would need to review many more than just four
studies and you would, of course, read each study in its entirety rather than reading the abstract. But for
this assignment you only need to concern yourself with the abstracts provided. They have been selected
as they are representative of the actual scientific evidence on DASH diet and CVD.
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Your job in this assignment is steps 3 & 4:
❸Critically evaluate each of the studies.
➍After looking at the individual studies, consider the totality of the scientific evidence and
formulate an answer to the question.
So what does it mean to critically evaluate a study? For this assignment it means looking at the
strengths and limitations of each study, in terms of the way it was designed and conducted, and also
looking at the results of the study: what did the study conclude about the relationship between DASH
and CVD.

Nutrition Research: Strengths and Limitations of Common Study Designs
In order to critically evaluate the studies described in the abstracts you need to know about the most
common types of study designs in nutritional research. In nutritional research there are main two
types of studies:
❶Observational studies
• Determines an association or correlation between diet and health
• Types of study:
• Prospective cohort study
• Case-control study (not discussed in this course)
• Cross-sectional survey (not discussed in this course)


❷ Randomized Controlled Trials (RCTs)
• Determines causation (or establishes a causal link) between diet and health
Observational studies are called such because, over the course of the study, researchers simply observe
populations and collect information from them about their diet and health status. Researchers do not
ask the population to change their lifestyle in any way. Observational studies determine whether an
association exists between an exposure and an outcome e.g. intake of nutrient X (the exposure) is
associated with a reduced risk of disease Y (the outcome). This is not the same as saying that nutrient
X causes a decline in disease Y and why this is so will be explained shortly.
The types of observational studies most commonly used in nutritional research are the prospective
cohort study, (a cohort is a group), the case-control study, and the cross-sectional survey. Only the
prospective cohort study will be discussed here.
While observational studies can determine an association between diet and health, only a randomized
controlled trial can determine causation or establish as a causal link between diet and health. In other
words, the results of an RCT allow you to say that a particular diet or food or nutrient causes an
improvement or a decline in health.
The discussion below explains why observational studies determine only associations between
exposures and outcomes, while randomized control trials can establish causal links.
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Consider the following hypothesis:
HYPOTHESIS: Nutrient X reduces the risk of disease
Y.
Prospective Cohort Study:
The figure opposite describes how, if you were a
researcher, you would conduct a prospective cohort
study to test the hypothesis of that nutrient X
reduces the risk of disease Y.
❶In a prospective cohort study you would select an
appropriate sample or cohort (or population), which
means that you would recruit a large group of
individuals who meet certain characteristics, to be
participants in your study. For this study it would be
a healthy population that is free of disease Y and you
might limit your cohort to middle-aged and older
adults, because this is when disease Y develops.
❷In this cohort, you would then determine the
dietary intake of nutrient X using food intake
assessment methods that we will be discussing later.
You would also collect other relevant personal
health information. ❸Over the course of the
study, and you might follow population for five
years or 10 years or longer, you track what
happens to the health of your population
particularly the occurrence of disease Y. This is why
the study is called a prospective cohort study
because you follow the population or cohort forward
in time, or you follow them prospectively.



❹At the end of the study you subdivide the participants into those that have a low intake of nutrient X
and those that has a high intake of nutrient X and in each of those groups you determine the proportion
of the group that developed disease Y over the course of the study. This will allow you to determine
whether there is an association between nutrient X and disease Y and whether it is consistent with the
stated hypothesis.
Important Note: In a prospective cohort study the dietary intake is measured at the beginning of the
study on disease-free participants and then the participants are followed over time to see if they
develop the disease. In better quality studies the dietary intake is often measured multiple times over
the course of the study, and a cumulative average intake is calculated, to account for any dietary
changes over time. This intake measurement would continue until the end of the study or until a
participant develops disease Y. The measurement of dietary intake, while the participant is healthy, is a
very important design element of the prospective cohort study because it ensures that the exposure,
i.e. nutrient X intake, occurs before the development of disease Y. This ensures what is called a proper














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temporal relationship, i.e. the exposure occurs before the disease and therefore it is possible for
nutrient X to have influenced disease Y.

At the end of the study, as noted, the study participants are divided into those that have a low intake of
nutrient X and a population that has a high intake of nutrient X (in most studies populations are divided
in to 3-5 groups of increasing intakes; for simplicity only two groups- low & high intake are shown here)
and in each of those groups you determine the proportion of the group that developed disease Y over
the course of the study. This will allow you to determine whether there is an association between
nutrient X and disease Y and whether it is consistent with the stated hypothesis. The most common
results are shown above:
❶You may find that there is no association between nutrient X and disease y i.e. the nutrient, across a
range of doses, has no impact on the development of disease Y.
❷Or you may find that there is an inverse association – increases in the intake of nutrient X are
associated with a decrease of disease Y- this result would be consistent with the hypothesis of the study.
❸Alternatively you may find that increasing intake of nutrient X is associated with increases in disease
Y, which is opposite to the stated hypothesis and is a direct association.

Limitation of Prospective Cohort Study
So let us return to the major limitation of observational studies – that one can only determine
associations rather than causal links. Why is this so? Consider our example of nutrient X and disease Y
and let us assume that you found an inverse association as shown in the table:

Nutrient X Intake Proportion of Disease Y Cases
Low High
High Low

The major limitation of observational studies is that you cannot be certain that the only difference in the
population that has a low nutrient X intake compared to the population that has a high nutrient X
intake, is nutrient intake alone. There could be other differences between the two groups that may be
influencing their risk of disease; in fact there always are. These differences are often referred to as

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confounding factors. A confounding factor is associated with both the outcome being investigated
(Cases of Disease Y) and the exposure (Nutrient X). For example, what if nutrient X intake in a
population happens to be lower in older individuals and we know that older people also get more
disease Y? So perhaps the association between nutrient X and disease Y is not really a dietary effect,
but is simply being influenced by age.
Fortunately, by doing statistical adjustment, you can eliminate the effect of age. The details of the
specific types of statistical approaches that do this, are beyond the scope of this course and I’ll leave it
for your statistics professors to teach you about the methodology. But in our example the effect of age
can be eliminated; age is a very common confounder and data are routinely age-adjusted. If there is a
real association between nutrient X and disease Y, the inverse relationship between nutrient X and
disease Y will still be observed, even after age-adjustment. If the effect was just due to age, there will no
longer be an association between nutrient X and disease Y after adjustment. Good quality studies will
typically include adjustment for many potential confounders, such as age, sex, smoking status,
socioeconomic status, physical activity, other dietary components besides the exposure of interest and
more. In your essay, when evaluating observational studies, determine whether adjustments for
confounders have been made.

One of the problems with confounding factors, however, is that you can only adjust for confounders
that you have identified and are able to measure accurately. Age can be measured very accurately;
other confounders may be more difficult to measure. Any confounding factors that are either unknown
or are subject to errors in measurement can result in the data being vulnerable what’s called residual
confounding, confounding for which adjustment is incomplete. It is because there is always a risk, in any
observational study, of residual confounding, that they are limited to demonstrating only associations
between exposure and outcome, but can never definitively establish a causal link.
For example, sleep pattern, a previously unknown confounding factor, has recently been shown to
influence body weight. Individuals who do not get enough sleep are at increased risk for obesity. As a
result researchers, studying obesity, are now asking study participants about their sleep habits and are
including sleep patterns in the statistical adjustments for confounding
factors. But this adjustment is relatively new and there are many studies
published on obesity that are unadjusted for sleep patterns. This residual
confounding may have influenced the conclusions of some of these
studies.
So returning to the prospective cohort study. The figure below shows the
final step in the study which is the correction, or adjustment, for
confounding factors ❶. This correction helps to strengthen the
conclusion
of any observational study, but it can never completely eliminate the
possibility of residual confounding. So the conclusion of the study can only
be that there is an inverse association between the intake of nutrient X and
the risk of developing disease Y.
In your essay, when critically evaluating the studies, determine whether
the study determined an association or established a causal link.
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In prospective cohort studies it is also important to consider how the exposure was measured. In the
example discussed here the exposure is nutrient X intake and for the assignment you have to do, it is the
adherence to a DASH dietary pattern which is typically measured in level of adherence based on
intakes (quintiles, tertiles, low vs high scores).
Food intake is commonly measured using a food frequency questionnaire (FFQ); participants are asked
to complete a survey about how often they consumed different foods. In the abstracts that you will be
reading for this assignment, the participants intake foods are derived from the food frequency
questionnaire.
Another method of measuring food intake, is the 24-hour recall, in which the participant is asked to
remember all the food they consumed the previous day. A 24-hour recall includes an interview (face-to-
face or by phone or via the Internet) between the participant and an interviewer trained to obtain as
much detail as possible about the participant’s food intake.
Regardless of the method used, good quality studies always validate their methodology. So what does it
mean to validate a method, for example to validate a food frequency questionnaire?

Validation means the method is compared to a more detailed measure of food intake and there is
good agreement between the results. For example, a food frequency questionnaire might ask a
participant how often he consumes carrots. For validation the participant might also be asked to
record his daily food intake, over multiple days. If the consumption of carrots as estimated from the
food frequency questionnaire is similar to the estimate based on the daily records, and this agreement
is seen for other foods and nutrients, then the food frequency questionnaire is considered to be valid
and can subsequently be used on its own to estimate food intake. In your essay, when evaluating
prospective cohort studies, consider whether the methodologies used to determine food intake are
described as validated.
Another important consideration is whether dietary intake was measured repeatedly over the course
of the study or only once. As noted above, in a prospective cohort study the dietary intake is
measured at the beginning of the study on disease-free participants and then the participants are
followed over time to see if they develop the disease. In better quality studies the dietary intake is often
measured multiple times over the course of the study, and a cumulative average intake is calculated, to
account for any dietary changes over time. This intake measurement would continue until the end of
the study or until a participant develops disease Y, at which point data collection of food intake would
stop. In your essay, when evaluating studies, consider whether repeated measures of food intake
were collected.
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Another important factor to consider is outcome measurement. Outcomes typically are divided into
two categories shown below: disease outcomes or measures of risk factors of disease. Disease
outcomes (often called “hard” outcomes) are commonly measured in prospective cohort studies
because they last long enough for disease to develop.

Risk factors of disease, rather than cases of the disease itself, are typically measured in RCTs, as will be
discussed below. Observing a reduction in risk factors does not absolutely guarantee that the
occurrence of the disease will be reduced. So, if your hypothesis is that there will be less disease, ideally
disease occurrence should be measured. In your essay, when evaluating studies, consider whether the
outcome measured was a disease or a risk factor for that disease.
For this assignment the outcomes that you will be looking at include CVD and the risk factors related to
the development of CVD, such as blood pressure. Background information on CVD and the types of risk
factors measured are described in Appendix 1 to assist you in understanding the terminology in the
abstracts.




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Randomized Controlled Trials
Up to this point we have discussed prospective cohort studies. They are
used to determine whether an association exists between exposure and
outcomes, but cannot determine causal links. In order to determine
causal links, researchers have to conduct another experiment, the
randomized controlled trial (RCT). Let’s look again at the nutrient X –
disease Y hypothesis. The figure opposite shows how the same
hypothesis can be tested, using an RCT. ❶Subjects are recruited and
randomized into a
control or comparison group ❷. The comparison group might be the
population’s everyday diet that happens to be low in nutrient X or a
special diet low in X. The intervention or treatment group would receive a
diet high in nutrient X, and this might be achieved by providing foods or
supplements high in the nutrient. ❸At the end of the experiment, the
proportion of the control group with disease Y would be compared to
the treatment group. If there is less disease in the treatment group, then it
can be concluded that nutrient X causes a reduction in disease Y.


How does this design allow causation to be determined? (See figure above) ❶When individuals
are randomized, confounding factors are equally distributed between the control and intervention
group for example, age is a common confounder, but because of randomization the average age of
both the
control group and the intervention group will be the same; the same will be true for socioeconomic
status and for all potential confounders, including those that are unknown. ❷So the only difference
between the two groups is the intervention. If the outcome differs in the treatment group compared
to the control group, a causal link is established. The intervention caused the difference.
While the RCT is a better design for establishing causation, it is also more demanding of its participants.
Unlike an observational study in which
participants are asked only to report
information, in an RCT, the
participants must change their
activities; in nutrition studies
participants are asked to change what
they eat. There are two ways that














2025-1 NFS284 Essay Page 17 of 29



dietary interventions are designed, as shown in the figure above.
❶One is the use of metabolic diets, in which all meals are prepared and provided to the participants.
While this is the most effective way to ensure that participants follow the treatment, it is very costly,
especially for a long study. ❷Instead of metabolic diets, participants are often given nutrition
education classes on how to select foods that conform to the control or the treatment diet. This approach,
while not as good as the metabolic diets, at ensuring that the treatment diet is consumed, is more realistic
– as in the real world, people would be given education and advice on what to eat, rather than the food
itself. In some studies, participants may be provided with some food products, a less costly alternative to
metabolic diets. In your essay, when evaluating studies, consider how the intervention was
delivered.
Two types of RCT designs: Parallel and Crossover design
The RCT described above, about nutrient X and disease Y, follows what is called a parallel design in
which the participants of the control group and the participants in the treatment group are different
individuals. It is also possible to have an RCT
in which the same individual participates in
the control group and also in the treatment
group. This is called a crossover design and
you will encounter it in one of your
abstracts, so it is briefly described here. Half
the group is randomized to receive the
treatment first and half is assigned to the
control (1). After the experimental period
ends, there is a washout period, a time for
any effects of the previous treatment effect
to wear off; then the two groups
“crossover” so those who received the
control diet now receives the treatment
and vice versa (2). Because this design
compares the response that one person
has to two diets, a crossover design can be conducted with a smaller sample size.

Limitations of RCTs and Observational
Studies:
One of the strengths of RCTs is that they
are able to show causation and for this
reason evidence from intervention trials is
considered stronger than evidence from
observational studies that test the same
hypothesis. One of the limitations of RCTs is
that they usually measure the effect of the
intervention on risk factors for disease,

rather than on the occurrence of the disease itself. This is because it is difficult to maintain an RCT for
very long periods of time, especially if you are asking participants to make substantial changes to their











2025-1 NFS284 Essay Page 18 of 29



diet; participants will tend to stop fully adhering to the intervention or drop out of the study
completely. On the other hand, because observational studies, are just that, observational, and do not
ask participants to make changes to their lifestyle, they can continue for many years and measure actual
disease outcomes. The major limitation of an observational study, of course, is that casual links
between exposure and outcome cannot be established, because residual confounding is always
possible. The figure, above, summarizes both the strengths and limitations of the two most common
types of nutritional research studies. In nutrition research, because of these limitations, as you are
doing in this essay, results from both types of studies are considered in making overall assessments of
the scientific evidence.

Additional Comment on Study Participants
For different studies different populations are recruited; sometimes healthy subjects are studied,
sometimes participants have some medical conditions; sometimes a study looks at only men or only
women; ethnicities may vary. When a hypothesis is tested it is desirable to see whether results support
the hypothesis across a variety of different populations. In your essay, when evaluating multiple
studies consider the variation in populations studied.
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Interpreting experimental results
In the previous section we looked
at the strengths and limitations of
different research design and
some of the study characteristics
that you should consider when
evaluating studies. In order to
answer the assignment question,
in addition to assessing the quality
of the studies, you have to also
correctly interpret the results of
the experiments. In the reporting
of results, one frequently
encounters measures of relative
risk.



To explain what is meant by relative risk see the figure above.
❶ Let’s assume that you are conducting a prospective cohort study which is made up of a group of 10
people with a low intake of a nutrient (in a real study you would have thousands of subjects, but here n=
10 is being used for simplicity).
❷ After many years of follow-up i.e. following the participants over a period of time, 4 out of 10
develop disease A.
❸So the frequency of the disease is 0.4
❹This information can be expressed as a ratio between two groups called a relative risk. Here we are
showing Relative Risk (RR) = 1 because the low intake group has been selected as the reference group.
The purpose of a reference group will become clearer when we look at a second group.
❺Now let’s consider the high nutrient intake group. Here only 2 out 10 people get sick.
❻The frequency of the disease is 0.2.
❼Compared to the low intake group, the RR for the high group is 0.5, i.e. high intake reduces the risk of
disease by 50%.
❽When reading studies, results are often presented in tables like the one shown here.
❾Compared to the reference group, which always has RR=1, the disease risk is increased in groups with
RR > 1 and decreased in groups with RR < 1. Which group is selected as the reference group is arbitrary
and decided by researchers based on how they want to present the results.
❿For example, the table shown here communicates exactly the same information as ❽, except the
reference group has been changed to the high intake group.
⓫ Finally, the calculation shown here is a RR. You will encounter similar ratios, such as a Hazard Ratio
(HR) or an Odds Ratio. There are differences in the way these ratios are calculated but they are
interpreted the same way as a RR and are all estimates of the same effect.






❿


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❶Here is table showing some relative
risks. The population here was divided into
5 groups or quintiles from lowest diet
quality score to highest dietary quality
score in a prospective cohort study that
lasted over 10 years. In the abstracts you
will be reading you will be looking at
comparison between low and high
adherence to the DASH diet.


❷After several years the relationship between the risk of CVD and diet quality was evaluated. Here
we see that as diet quality increases, CVD risk decreases i.e. RR is less than 1.
❸ Specifically, comparing lowest to highest quality diet scores, the RR dropped from 1 to 0.61, a drop
of 0.39 or 39%.
❹ When researchers see results like this, the next question they ask is whether the difference in
disease risk that is observed between high and low quality diet, is due to chance, or indicates a
meaningful effect of diet quality on disease risk. In order to do this researchers conduct statistical
analysis.
In order to correctly interpret the results of statistical analysis, which you will encounter in this
assignment, a few statistically concepts have to be considered.
• Null hypothesis
o This is a somewhat counterintuitive concept. Scientists tend present their hypotheses in
a positive light, e.g. increased diet quality results in decreased disease risk. But the null
hypothesis describes a situation of no effect e.g. diet quality will have no effect on
disease risk; there will be no difference in disease risk between groups, whether
consuming high or low quality diets.
• Alternative hypothesis
o This is an hypothesis that is an alternative to the null hypothesis e.g. There will be a
difference in disease risk between groups consuming high quality diets compared to low
quality diets
• Model
o Mathematical equations, used in statistical analysis, that best fit the data
• Probability or P-value
o Expressed as a decimal between 0 and 1, where P = 0 means there is no probability of
an event occurring and P = 1, which means there is a certainty that an event will occur.
P-values can also be expressed as % e.g. p = 0.50 or 50% probability of an event
occurring
o Determines the probability that the observed difference (or greater difference) between
groups being compared would occur with repeating experiments assuming:
▪ The null hypothesis is true
▪ All assumptions used in the mathematical model are correct



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▪ Chance alone is operating
Here a p-value has been calculated for the RR data we
discussed earlier, P-value = 0.002. What does this mean?
A P-value indicates that a comparison is being made between
at least two groups, so the first step is to know what is being
compared. Here the comparison is between the relative risk of
1 and the relative risk of 0.61; a comparison of the lowest vs highest diet quality groups.
P=0.002 means, assuming the null hypothesis is true, the model assumptions are correct, and chance
alone is operating, that a difference as large as (or larger than) the one observed, would occur in 1 out
of 500 experiments.
One way of looking at the data is that the null hypothesis is true and that the data observed here is
essentially an extremely rare (1/500) result. It is important to recognize that this a legitimate way of
interpreting the data. Another way, however, and this is what most scientists would conclude, is that
the small P-value of 0.002 is strong evidence against the null hypothesis. Researchers would say that
there is a statistically significant difference in disease risk in the low diet quality group compared to the
high diet quality group. The data suggests that, indeed, as diet quality increases, the CVD risk may
decrease.

Level of significance
There are some conventions that biomedical researchers typically use for interpreting P-values.
Researchers say that there is a statistically significant difference between groups when the calculated P-
value is less than 0.05 and there is no statistically significant difference when P > 0.05. Alternatively,
when p <0.05 there is evidence to reject the null hypothesis, while p > 0.05 evidence favours not
rejecting the null hypothesis.
The 0.05 (or 5%) cut-off, which is called the level of significance, is arbitrary and other levels of
significance e.g. p <0.01 or p <0.1 can be used, if appropriate for the research question being addressed.
All statistical results have to be interpreted with common sense e.g. there is really no meaningful
difference between study results with a P = 0.049 and P= 0.051 even if technically one is significantly
different and for the other there is no statistically significant difference. It is important to recognize the
word significant is used here in a very strictly defined way, not just as a common word to mean
important or substantial. It refers to a statistical assessment and will be used this way in the abstracts.
Also a “statistically significant difference” does not PROVE that the null hypothesis is false, although
results of studies are often misinterpreted to mean this, especially in the popular media. Similarly
results that are not statistically significant do not PROVE that the null hypothesis is true. These concepts
are summarized in the table below. There is always uncertainty associated with any conclusions drawn
from an analysis of statistical significance, especially from a single scientific study.
That is why it is important to look at multiple studies, as you will do in this assignment, to see how
consistent the results are. When multiple studies look at the same problem, and draw similar
conclusions this increases confidence that the conclusions are meaningful. In your essay, when
evaluating the results, consider the overall consistency of the results across multiple studies.

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Statistically significant: P < 0.05 Not statistically significant: P > 0.05
Evidence favours rejecting the null hypothesis.
But does not prove that the null hypothesis is
false, only that the evidence supporting it is
weak; the null hypothesis, however, may still be
correct.
Evidence favours not rejecting the null
hypothesis, but does not prove that the null
hypothesis is true; only that the evidence
supporting it is strong; but the null hypothesis
may still be incorrect.

95% confidence intervals
There are other ways to present the results of a statistical comparison of relative risks. For relative risks
a range of values called a 95% confidence interval (95% CI) is often
reported, instead of a P-value. For the relative risk shown opposite it is
(0.49 – 0.75).

What does this interval measure? It indicates that there is a 95%
probability that the true relative risk lies within the interval. While 0.61 is
the best estimate of the relative risk, the value can be as low as 0.49 or as
high as 0.75. Imbedded in the 95% CI is information about the statistical significance of the relative risk.
When comparing an interval to the reference group (which has RR=1) if the interval includes 1 than the
results are not statistically significant. If 1 is not included in the interval, such as the example here (0.49-
0.75) there is a statistically significant difference. The 95% confidence interval does not tell you the
exact P-value, only that it is greater or less than 0.05. A separate calculation needs to be done to
calculate a P-value, as was done here (P = 0.002). The interpretation of CIs is summarized below:

Confidence intervals are very useful for making comparisons between pairs of groups, such as the
comparisons described above between the lowest and highest diet quality categories. But in most
observational studies there are multiple categories. Pairwise comparisons are not that useful. In many
studies what you want to know is whether there is a trend of increasing or decreasing disease risk
across all intake categories i.e. is there an association between exposure and outcome? This is generally
of greater interest than whether there is a statistically significant difference between the reference
group and one other category. To determine whether an association exists another type of statistic is
calculated: p for trend. To illustrate this the chart below shows the data on diet quality and CVD risk
previously discussed along with the additional data on the relationship between diet and cancer.
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Also shown is the calculation for P for trend
which is statistically significant for CVD, P
trend <0.001, well below the conventional
P
<0.05 threshold for significance and is not
significant for cancer (P for trend = 0.68). As
was noted earlier when you see any P-value
you need to know what is being compared.
The chart below indicates the comparisons being made:
The flat line indicated by the red arrow is the
theoretical representation of no effect or the
null hypothesis. The curve indicated by the
purple arrow has a p for trend greater than 0.05
suggesting that it is not significantly different
from the flat line. There is no apparent
association between diet quality and cancer. The
curve indicated by the yellow arrow has a p for
trend of less than 0.05 indicating that there is
significant difference in trend compared to a flat
line. The results indicate an inverse
association between diet quality and CVD risk.


In this assignment you will see results reported with p-values, confidence intervals, and p for trends
and you will have to interpret their meaning as it relates to the relationship between DASH diet and
CVD. Prospective cohort studies typically report confidence intervals and, more importantly, p for
trend, which indicates whether there is an association between exposure and outcome. In your essay,
when assessing the results of the prospective cohort studies, the focus should be on p-trends as they
are indicators of an association between exposure and outcome.
RCTs report between group differences, e.g. the effect of the treatment group and whether it differs
from the control group. A P-value comparing treatment vs control group indicates whether there is a
significant difference between the two groups. In your essay, when assessing the results of the RCTs,
the focus should be on these P-values and whether they are statistically significant or not.
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Appendix 3: Tips for writing your essay
Getting started with your essay:
• Read the question carefully
• Read each abstract carefully.
• To help you understand the study, identify the following characteristics, for each of the abstracts as
shown in class, during the lecture on nutrition research:

• Observational studies:
1. Study design
2. Population; age, gender, healthy, etc.
3. Study location
4. Exposure
5. If dietary intake was assessed, how was it measured? e.g. FFQ, validated? Repeated?
6. Outcome(s): disease or risk factors
7. Duration of study; in observational studies the term “follow-up” is used
8. Result: Was an association between exposure and outcome observed? Statistical
significance?
9. Adjustment for confounders (Y/N)
• Randomized controlled trials (RCTs)- the items that differ from observational studies are shown
in bold:
1. Study design
2. Population; age, healthy, etc.
3. Study location
4. Intervention (s): Metabolic diet or education
5. Comparison/Control Group
6. Randomization Y/N
7. Outcome(s)
8. Duration of study
9. Result: Did the intervention impact the outcome? Statistically Significance?
• Place each one of these points on an index card:
• Limit each card to one concept or point. The less written on each card the easier it will be to
order and integrate the ideas into a final essay.
• Paraphrase. Putting information into your own words at this stage is an effective way to
avoid plagiarism. If you must copy verbatim, be sure to use quotation marks, so you’ll know
that this is information you have to paraphrase later when composing your essay.
• ALSO ADD: The strengths and limitations of each study
• ALSO ADD: Information from Appendix 2 related to sentences, in bold, that begin: “In your
essay…”
• Examples:
•



• Sort through the cards looking for the best way to support the answer to the assignment question:
Black and White 2000
Strength and Limitation:
Limitation: Adjustment for confounders made but residual
confounding still possible
Black and White 2000
Study Design:
Prospective cohort study
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• Look for similarities and differences between studies; for example group all the “study
design” cards together, all the “population” cards with results together to more easily make
comparisons
• Put the cards in an order that allows you to address the essay question in a logical and
sophisticated manner.
• At this point it is a good idea to re-read the assignment question and the abstracts again to
see if there are any additional ideas that you missed on the first reading.
• Creating a detailed outline, at this point, might also be helpful.
• Electronic alternatives to using index cards:
• PowerPoint: Write one idea/slide and use the slide sorter function to order the
cards.
• Word: Create a list of ideas and cut and paste to alter the order of ideas.
• Think about your introductory and concluding paragraphs- for a 500 word essay these need not be
more than 2-3 sentences.
• Your introduction should summarize how you are answering the question. The reader
should know by the end of the first paragraph how you are answering the question.
• Your conclusion should be strong and should sum up your position in a way that is not an
exact repetition of the introduction.
• Use multiple short paragraphs. They are easier to read than longer paragraphs, and are effective
signals to the reader when you are changing topics.
• Be sure to create paragraphs that transition logically from one to the next- this produces a
good “flow”
• Make sure that your essay is written in a persuasive style – you are trying to convince the
reader that your assessment of the studies is reasonable.
• Not sure where to begin. JUST START WRITING. The act of putting ideas in your own words will help
you to see how to organize your essay.
• Revision and Proofreading: After you have completed your first draft, if time permits, don’t read the
essay for at least 24 hours. Returning to the essay after a break allows you to look at it with fresh
eyes and spot areas that need improvement more readily. Rather than editing solely from a
screen, it is also recommended that you look at a hard copy of your essay at least once during your
revision process. It is usually easier to spot errors and get a sense of the total essay when looking at
a hard copy.
Be sure to avoid these common essay flaws:
• Flaw 1: Not making your position clear.
• Be sure that you clearly state your evaluation of scientific evidence in the introductory paragraph – do you
conclude that the evidence is very convincing, not convincing, or moderately convincing, etc.
• Flaw 2: Not including all the important points in bold from Appendix 2. These points should be given the following
priority:
• In order to get at least an A- for scientific content the major points listed below must be integrated into a
PERSUASIVE ARGUMENT SUPPORTING A PARTICULAR ANSWER to the assignment question: Based the
studies described in Appendix 1, how convincing is the scientific evidence that the DASH diet decreases the
risk of death from cardiovascular disease?
• In your essay, when evaluating observational studies, determine whether adjustments for
confounders have been made. Be sure to indicate whether the adjustment for confounders is a
strength or imitation when evaluating the evidence.
• In your essay, when critically evaluating the studies, describe whether the study determined an
association or established a causal link. Note the relevance of residual confounding in cohort
studies. Be sure to indicate whether this is a strength or limitation of the evidence.
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• In your essay, when evaluating studies, consider whether the outcome measured was a disease or
a risk factor for that disease. Indicate whether what was measured was a strength or limitation
when evaluating the evidence.
• In your essay, when evaluating the results, consider the overall consistency of the results across
multiple studies. Indicate how consistency or lack of consistency influences the strength of the
evidence.
• In your essay, when assessing the results of the prospective cohort studies, check P for trend and
whether it is statistically significant, as it is an indicator of an association between exposure and
outcome. If p-trends are not reported, try to assess the likely trend based on the statistical
significance of the confidence interval of the risk ratio.
• In your essay, when assessing the results of the RCTs, the focus should be on the P-values
comparing groups, e.g. treatment vs control and whether they are statistically significant or not.
• These are additional MINOR points that if included in the essay can further enhance the grade provided the
points are well-integrated into a persuasive argument supporting a particular answer to the question:
• In your essay, when evaluating prospective cohort studies, consider whether the methodologies
used to determine food intake are described as validated. Be sure to indicate whether this is a
strength or limitation.
• In your essay, when evaluating studies, consider whether repeated measures of food intake were
collected. Indicate whether repeated measures or their absence is a strength or limitation.
• In your essay, when evaluating multiple studies consider the variation in populations studied.
Identify whether population differences indicate a strength or a limitation of the evidence.
• In your essay, when evaluating studies, consider how the intervention was delivered-metabolic
diet, some food provided, or education, and indicate the strengths or limitations of the method
used.

• Flaw 3: Discussing each study in isolation without making connections between studies or without noting similarities
and differences between the study characteristics.
• Avoid an essay that contains four disconnected paragraphs describing each study in isolation. You have to
make connections and transitions between your paragraphs in a logical fashion to support the answer to
your question.
• Also don’t feel your entire essay has to be study-by-study. Consider discussion of multiple studies in a single
paragraph, grouped by relevant characteristic such as results, study design, etc. For some of the points you
want to make, this might be a better approach.

• Flaw 4: Summarizing the study results, without making an evaluation of strengths and limitations of study design e.g.
prospective cohort study or RCT. Often students make the evaluation of how convincing the scientific evidence is by
looking only at the results, e.g. were statistically significant results found, without saying much about the study
design. See points listed in flaw 2 above. You have to discuss study design in the essay.
• Flaw 5: Ignoring an abstract either through carelessness or because its content was difficult to integrate into the
discussion. You must discuss all abstracts in your essay.
• Flaw 6: Presenting only the strengths or only the limitations of a study. The evaluation of the studies must be
balanced. You must acknowledge the limitations of studies even if they are consistent with your position.
• Flaw 7: Not citing references properly. See Appendix 4 for instructions.




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Appendix 4: How to format references
This assignment assumes you have completed the Science Writing Quiz and understand the concepts
of paraphrasing, in-text citations and bibliographies.
Sources used for the essay should be cited within your text, using the NAME-YEAR format of the Council
of Science Editors, and listed in a bibliography, alphabetically by first author, at the end of the essay.
(See important note below about multi-author papers). See the document: How to cite and format
references for more details.
How to cite an abstract from a database:
In this assignment your sources are abstracts from databases such as PubMed. It is essential in your
bibliography that you indicate that you used abstracts, as you have NOT read the full-text article. This is
done by preparing the bibliographic reference as described in the document noted above for a journal
article but including the phrase [(Name of database) Abstract] after the title: e.g. Authors .Year. Title.
[PubMed abstract] Journal title Volume (issue): inclusive pages.
Important note about multi-author papers:
• Never change the order of the authors of a study. The first author of a study is the person that
spent the most time preparing the paper and has earned the right to be listed first. The first author
is often referred to as the lead author.
• Your bibliography should be alphabetical by first author. This means that if the first author of a
paper is Brown and a second paper has the first author Green, then the Brown paper is listed before
the Green paper. If two papers have the same first author than the order of the papers is decided
based on the second author’s name.
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Appendix 5: How the essay is graded:
The essay will be graded based on two major criteria:
Fluency (10%): Overall: Was the writing clear and easy to follow?
Scientific content (90%): Overall: Was the scientific evidence effectively used to answer the question?
Use the checklist below to help you evaluate your essay:

Fluency:
• Does your writing flow readily from introduction, to body, to conclusion with good transitions
from idea to idea?
• Have you presented your ideas in an order that is logical and easy for the reader to follow?
• Is the language of your essay clear and concise?
• Does your introduction clearly state the answer to the question and did the writing conclude
with appropriate emphasis?
• Are your sources properly paraphrased?
• Are your in-text citations and bibliography properly formatted? (Errors or omissions in-text
citations: deducted: 1 to 4%/100%; Errors or omissions in bibliography: deducted: 1 to
4%/100%)
• Is your essay within the stated 500 word limit? Note a 15 word overage will be forgiven after
which deductions will be made. Excessive length: deducted: 2% to 6%/100%
Scientific content:
• Did you use relevant information from all the abstracts to answer the question?
• Is the answer to your question well-supported by the evidence presented?
• Does your essay include a comprehensive analysis of the studies’ strengths and limitations?
o Did you include the information indicated in Appendix 2 that should be in the essay?
(see bolded sentences that begin “In your essay…”)
• Did you include a discussion of the results of the studies including their consistency and
statistical significance?
o Did you include the information indicated in Appendix 2 that should be in the essay?
(see bolded sentences that begin “In your essay…”)
• Did you include an overall assessment of the scientific evidence?
Policy regarding re-reading of assignment:
If you have substantive concerns about the grading of your essay, after it is returned, you may request a re-read.
More information on how to request a re-read will be provided later in the term. If no comments are included, Dr
G will not re-read your essay. Your mark can go up, down, or stay the same. Please note that the higher your
original grade, especially >80%, the less likely an upward adjustment in your mark will occur. The deadline for
submitting requests will be posted on Quercus. This deadline will not be extended. Dr G will advise students
when re-reads have been completed. Her decision on grades is final.
Appendix 6: Submitting your essay online
A link is available on Quercus for you to submit your essay. Your essay must be a Word document: doc
or docx to facilitate the determination of word count. Quercus will block your submission if the file
format is incorrect. On Quercus, online submissions will automatically be submitted to Turnitin, but you
will have to agree to the Turnitin license agreement. See the course syllabus for more information on
Turnitin as a plagiarism prevention tool and alternatives.
2025-1 NFS284 Essay Page 29 of 29



Formatting: Please use Calibri font size 12 for your essay and single-space. Be sure to include your
name and student number at the top of the page. DO NOT include a title page, a title, or re-write the
essay question. This information is not necessary for this assignment and increases the amount of time
TAs spend scrolling online.
Appendix 7: Policy regarding the late submission of essay: Please see the course syllabus for the
late submissions policy.

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