15

Question 1

Nutrition Survey

Answer 1

Eg. National Health and Nutrition Examination (NHANES) – info on food and nutrient intake in the US
Interdepartmental Committee on Nutrition for National Defense (ICNND) – organized in 1955
-to help developing countries assess nutritional status, identify problems, provide solutions
-produced manual (Manual for Nutrition Surveys 2nd Ed. 1963 NIH) for collection of nutrition survey data and interpretation of results
Diet increasingly recognized as determinant of health and disease

Question 2

Dietary Intake – to evaluate nutritional adequacy

Answer 2

A) Group Dietary Data
Food Disappearance Data
http://www23.statcan.gc.ca/imdb/p2SV.pl?Function=getSurvey&SDDS=3475&Item_Id=122424&lang=en
determine total food available
evaluate amount utilized (subtracting exports, fed to livestock, non-food uses, wastage)
calculate per capita intakes
Household Food Intakes
survey household member responsible for food purchase, meal planning
ask to keep record of purchases and menus for one week

Question 3

B) Individual Dietary Methods

24-hour Recall

Answer 3

collect in interview
visual aids (food models, pictures, measuring utensils) often used to estimate quantities
strengths:
quick, easy to administer
can accommodate diverse populations, ethnic groups
limitations:
variation in food selection on different days
oftern do for 2 week days and one weekend day

Question 4

2. Food Records or Diaries

Answer 4

subjects measure or estimate and record foods consumed over period
generally over 3-7 days, or at periods in a year
requires good instructions, demonstrations
generally for dedicated, motivated subjects (may not represent all population)

strengths:
doesn’t rely on memory
more accurate (although not error free)
limitations:
period typical? 
subjects who agree to participate may not 	be representative

Question 5

3. Diet Histories

Answer 5

interview of usual daily intakes, or food frequency questionnaires
should validate instrument with pre-tests
Eg. cross-check with food frequency check list or 3-day food records
often based on food groups with similar nutrient values
can be used in population studies to seek etiology of disease (eg. cancer, heart disease)

Question 6

Epidemiologic Descriptive Research (Epidemiology)

Answer 6

Describes: -distribution of disease
-associations between possible causal factors and disease
Generates hypotheses that can be tested by analytical methods
Eg. -Survey by Kromann and Green described difference between Danes and Eskimos in heart attack mortality
Bang et al used dietary intake/food composition analysis to show a difference in type of dietary fat
Clinical trial showed supplementation of omega-3 FAs decreased triglyceride levels in Danes

Question 7

Epidemiologic Approaches to Diet and Disease

Answer 7

Lind (1753) – controlled clinical trial on scurvy
Goldberger – used epidemiologic methods to show pellagra was nutritional deficiency related to corn meal subsistence
Correlation Studies
association between dietary factors and disease incidence
generally ecologic (ie. different locations)
often from food disappearance data
Eg. colon cancer incidence in different countries versus meat consumption
may suggest causal relationship but need caution
other confounding variables may explain relationship (eg. Lifestyle , sugar, alcohol)

Question 8

2. Special Exposure Groups

Answer 8

groups with unusual diets – opportunity to study relation of diet and disease
Eg. Seventh-day Adventists – largely vegetarian, colon cancer mortality about half that of normal population
Limitations similar to correlations
Eg. lower colon cancer in Seventh-day Adventists may be due to lower alcohol, higher fruits and veggies – need to adjust for alcohol, more vegetables…

Question 9

3. Migrant Studies and Secular Trends

Answer 9

useful to address genetic versus ecological factors
eg. cancer incidence in populations migrating to new location
acquire incidence rate of new location?
May take generations

Question 10

4. Case-Control Studies

Answer 10

compare people with certain disease (case) with comparable group without (control)
obtain dietary history (eg. by interview)
eg. cancer patients report higher alcohol consumption
avoids some limitations of correlational studies (ie. Control groups)

Question 11

5. Cohort Studies

Answer 11

prospective studies – diet of group of healthy individuals assessed and group followed over time for incidence of disease
analyze dietary characteristics relative to disease occurrence
avoid methodological problems of other epidemiologic studies
improved validity of dietary assessment
practical limitations
may need large number for statistical power
time
expensive
often use food frequency questionnaires (with inherent limitations)

Question 12

6. Cross-Sectional Study

Answer 12

Similar to cohort (prospective) but measurements made at once with no follow-up
eg. interview people about health and dietary habits
eg. prevalence of hypertension related to salt intake
strength – don’t need to wait for disease development
weakness – difficult to establish causal relationship

Question 13

7. Controlled Trials

Answer 13

group given inactive substance and other 	given dietary constituent that may affect 	disease risk
Eg. blueberries on heart disease risk
ie. experimental design
preferably randomized
preferably double-blind

Question 14

8. Meta-Analysis and Pooled Analysis

Answer 14

Eg select only prospective studies or other of high quality
need to be systematic and complete or may introduce bias
sometimes have problems comparing studies Eg. Different statistical methods)