Final

Question 1

What are the non-experimental/observational study designs?

Answer 1

• ecological
• cross sectional
• prospective cohort/longtitudinal
• retrospective
• case control

Question 2

What are the experimental/interventional study designs?

Answer 2

• randomized control trials
• pre-post
• repeated measure
• crossover

Question 3

Randomized controlled trials

Answer 3

The “gold standard” of experimental designs. Randomized - double blinded. Expensive and sometimes not feasible. Careful selection of participants, controls for as many extraneous variables. Designed to answer ONE specific question.

Question 4

Pre-post study

Answer 4

baseline measurement of dependent variables –> intervention –> after measurement of dependent variables

More open to bias, not randomized. Simple design, less expensive. Long - attrition.

Question 5

Repeated measure study

Answer 5

intervention & baseline measurements –> day 14 measurements –> day 28 measurements –> end intervention measurements

Would be made stronger with a control. Designed to answer one question.

Question 6

Crossover study

Answer 6

2 levels of treatment. Everyone receives the intervention. Before and after measurements of each person for each treatment arm. Each person serves as their own control.

Question 7

Ecological study

Answer 7

Looks at variables observed in geographical regions. Describes and compares different populations. Can establish associations and support further research. Not individual level data - cannot establish causation.

Question 8

Cross sectional study

Answer 8

“Snapshot” measurements at a single point in time. Variables of interest collected at the same time. Identifies associations between variables and can be used to generate a hypothesis. Can compare two or more groups. Limitations are that only a single point in time - cant establish causation. Sample selection is really important to generalize results.

Question 9

Prospective cohort (longitudinal) study

Answer 9

Data collected on variables of interest from the same individuals (potentially multiple times). e.g. progression of a disease, impact of aging etc. Participants usually have a common characteristic. Can assess causal associations and assess many variables at the same time. Limitations are they are very long and attrition is likely, expensive.

Question 10

Retrospective cohort study

Answer 10

Data is collected from existing records. Examines if individuals with differing levels of a factor have different outcomes. e.g. if obesity at the time of surgery will increase complications later. Cohort is a defined group (e.g. all women who had a baby in the last 10 years). Strengths are inexpensive, no burden on the cohort, can establish some causal association. Limitations is that the data may not be present.

Question 11

Case control study

Answer 11

2 groups - one with the condition and one without. Examines variables in the past (risk factors). Different than retrospective cohort –> the outcome is present and looking back at risk factors. e.g. how to patients characteristics at the time of the surgery differ between those who do and do not develop complications? strengths are you can examine rare conditions, assess causal conditions, cost and time efficient. Limitations are retrospective - data may not be available, relies on recall, the right controls are needed.

Question 12

Types of evidence

Answer 12

• Convincing: strong, consistent, unlikely to change
• Probable: compelling but not quite strong enough to be convincing
• Limited evidence – suggestive: general consistency in the data
• Limited evidence – no conclusion: too inconsistent
• Substantial effect on risk unlikely: enough evidence to rule out a connection

Question 13

Types of dietary intervention

Answer 13

• controlled feeding studies

- behavioural counselling studies

Question 14

Strengths and Limitations of FFQ

Answer 14

Strengths: high respondent rate, can assess a number of people at the same time, relatively low participant burden, lower cost, generally does not affect eating behaviour

Limitations: lacks detail, requires literacy, different populations respond differently, problem with assessing foods in recipes

Question 15

Strengths and Limitations of 24h recall

Answer 15

Strengths: suitable for illiterate subjects, low participant burden, high compliance, unlikely to interfere with diet, can be detailed

Limitations: relies on memory, relies on portion size estimates, only a “snapshot”, costly for face to face, underreporting is common

Question 16

Strengths and Limitations of food diaries

Answer 16

Strengths: intake is quantified, does not rely on memory, can include weekends, could be relatively accurate if subjects are trained

Limitations: recording can influence dietary choices (bias), expensive, high participant burden, underreporting

Question 17

Criteria for establishing causation

Answer 17

Temporality (exposure precedes outcome)
strength of association
dose response (greater exposure = higher risk)
consistency of results 
biological plausibility

Question 18

What are the functions of choline?

Answer 18

• Phosphatidylcholine (structural component of biological membranes, transports lipid molecules, structural component of the brain)
• acetylcholine (a neurotransmitter)
• sphingomyelin (nerve fibre myelination)
• methyl donor
• component of plasmalogen
• component of platelet activating factor

Question 19

What are the effects of choline deficiency?

Answer 19

Steatosis (fatty liver)

• due to the impairment of VLDL secretion from the liver
• likely due to the fact that choline is the precursor for PC, the main phospholipid in VLDL particles

Question 20

Who is most susceptible to choline deficiency?

Answer 20

men and postmenopausal women

Question 21

What effects does choline have on CVD?

Answer 21

choline is important for the methylation of Hcy into Met. High Hcy plasma concentrations are related to CVD.

Question 22

What effects does choline have on intestinal health?

Answer 22

PC is a component of the intestinal mucus barrier

Question 23

What role does Vit D play in the body?

Answer 23

increases absorption of Ca and P
increases bone mineralization
induces differentiation of immune cells
inhibits proliferation and ingiogensis in tumour formation

Question 24

What is the best biomarker of Vit D exposure?

Answer 24

Serum 25(OH)D

Question 25

What are the two forms of vitamin D?

Answer 25

D3 cholecalciferol (fortified foods)
D2 ergocalciferol (plant foods i.e. mushrooms)

Question 26

What influences vitamin D status?

Answer 26

Latitude
Pollution
Skin pigmentation
Sun screen

Question 27

DRI for vitamin D

Answer 27

600 IU/d

Question 28

What effect does Vitamin D have on CVD?

Answer 28

low 25(OH)D status associated with CVD risk factors

Question 29

What effect does vitamin D have on immune effects?

Answer 29

vitamin D down regulates inflammation by macrophages
vitamin D receptor is present on immune cells and important for normal function of T cells
poor vitamin D status associated with increased risk for infectious disease

Question 30

What effect does vitamin D have on diabetes?

Answer 30

vitamin D important for the normal function of beta cells in the pancreas which play a role in insulin production and release

Question 31

What effect does vitamin D have on obesity?

Answer 31

when exposed to the same amount of UVB rays, serum vitamin D only goes up half that of a normal weight person in an obese person
- adipose tissue may act as a sink - vitamin D stores may be higher just not released

Question 32

Acute inflammation

Answer 32

immediate defensive reaction to tissue damage or injury

• usually less than 3 weeks
• neutrophils recruited to site
• variabel systemic effects
• not necessarily associated with tissue destruction
• followed by healing and repair

Question 33

Chronic inflammation

Answer 33

inordinate activation and/or insufficiently regulated immune system

• long duration
• macrophages, lymphocytes and their mediators predominate
• significant tissue damage
• systemic effects

Question 34

What are the two processes that chronic inflammation can originate from?

Answer 34

1) follows acute inflammation

2) inflammation begins as an insidious, subclinical low grade process (chronic disease)

Question 35

Biomarkers of inflammation

Answer 35

C- reactive protein (gold standard)
IL-1
IL-6

Question 36

How do n-3 PUFAS reduce inflammation?

Answer 36

• change the membrane receptors and signals on inflammatory cells
• modulate expression of inflammatory and anti-inflammatory genes
• regulate eicosanoid production
• promote the function of T cells to regulate inflammation