Nutritional epidemiology examines the complex interactions between socioeconomic, environmental, and genetic factors influencing nutritional status and disease outcomes through various study designs and dietary assessment methods. Assessment of nutritional status is crucial for developing public health strategies to address malnutrition and requires a combination of direct and indirect methods, including dietary recalls, biochemical tests, and anthropometric measurements. The document emphasizes the importance of accurate data for effective policy-making and resource allocation in combating malnutrition.

1. Nutritional Epidemiology &
Nutritional Assessment

2. Introduction
• Nutritional status determined by complex
interaction of socioeconomic and environmental
factors and genetic factors
• NE provides scientific way of understanding these
determinants and cost-effective
interventions/policies and an evidence base
• From evidence to policy – issues of decision
making
• Nutritional guidelines; guidelines on nutrition and
physical activity

3. Key constructs in epidemiology
• Epidemiology deals with the association between
exposure and outcome
• Typically, exposure is a variable that is associated
with presence or absence of a disease
• In nutritional epidemiology the main exposure of
interest is dietary intake
Example
• Exposure: Inadequate dietary intake; dietary fat
intake
• Outcome: stunting, anemia, CVDs

4. Types of studies
• Observational
– Cross-sectional
– Ecological
– Cohort
– Case-control
• Experimental
– RCT
– Community interventions

5. Assessment of nutritional status
• Assessment of nutritional status of community is one of the first steps in
the formulation of any public health strategy to combat malnutrition.
• Aims
– to determine the nutritional status of individuals or populations
– to determine the type, magnitude and the distribution of malnutrition
in different geographic areas
– To find out the relationship between diet and diseases
– to identify ‘at risk’ groups
– to determine the contributory factors
– to evaluate the efficacy of nutritional interventions
• Actual evidence of the exact magnitude of malnutrition is essential to
sensitize administrators and politicians to obtain allocation of material and
human resources and to plan appropriately.

6. Sequence of nutritional deficiency and specificity of assessment of nutritional status
Sequence of deficiency Components of nutritional status assessment
Dietary intake Dietary assessment
Tissue reserve
Body fluid level Laboratory and biochemical estimation
Intracellular level
Functional performance Biophysical, functional
Clinical signs and symptoms Clinical examination
Permanent change, morbidity & mortality Anthropometry, Vital Health Statistics

7. • Nutrition is assessed by two types of methods;
direct and indirect.
• The direct methods deal with the individual
and measure objective criteria, while indirect
methods use community health indices that
reflects nutritional influences.

8. Methods of nutritional assessment
• Direct methods
– Dietary assessment
– Laboratory and biochemical assessment
– Biophysical or radiological examination
– Functional assessment
– Clinical examination
– Anthropometry
• Indirect methods
– Vital health statistics
– Ecological variables (crop production, etc)
– Economic factors (e.g. PCI, population density & social
habits)

9. Dietary methods
• Short time recalls
– 24 hour recall, validation by observation and then administering the
questionnaire, limitation – variations in daily food intake
• Food diaries
– Meal by meal registers of type and quantity of food consumed for 3 to 7 days,
time consuming, participants should measure food intake, requires a level of
literacy
– Both 24 hour recall and food diaries cannot be used in case-control situations.
Multiple 24 hour recall can be used for cohort studies. Both can be used for
validation / calibration of other methods
• Food frequency questionnaires (FFQ)
– For long term dietary intake. List of all foods (including beverages) consumed
and time scheme for the respective items. Two types – Qualitative and
quantitative. Quantitative one provides information on serving sizes. Usually
self-administered, easy to be administered
• Dietary history since early life
• Observed food consumption

10. Dietary recall
• 24 hour recall
• Retrospective recall
• For short term dietary assessment
• Often done more than one recall to take care of daily variations
• Steps – (a) 24 hour recall - A quick list of foods eaten or drunk (b)
validation by collection of detailed information or observation - time,
description of the food, brands, recipes, quantity (c) administering post-
recall questionnaire
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wl3Hg
• Food recall kit can be used to asses the quantity of food consumed
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KMA
• Usually chronological recall of items consumed
• Difficult with children, aged, and illiterate
• Requires support of other methods as data may not be representative

11. Food & physical activity diary

12. Food frequency questionnaire

13. Interpretation of Dietary Data
• Qualitative Method
• using the food pyramid & the basic food
groups method.
• Different nutrients are classified into 5
groups (fat & oils, bread & cereals, milk
products, meat-fish-poultry, vegetables &
fruits)
• determine the number of serving from each
group & compare it with minimum
requirement.

14. Interpretation of Dietary Data/2
• Quantitative Method
• The amount of energy & specific nutrients in each
food consumed can be calculated using food
composition tables & then compare it with the
recommended daily intake.
• Evaluation by this method is expensive & time
consuming, unless computing facilities are available.

15. Bio-chemical / Laboratory methods
• Static tests– measures nutrient or metabolite in tissues or
fluids and helps in identifying intermediate stage of
nutrition deficiencies / excesses / reactions. Useful at
population levels and used in national level surveys
– Hemoglobin estimation is the most important test, & useful
index of the overall state of nutrition. Beside anemia it also tells
about protein & trace element nutrition.
– Stool examination for the presence of ova and/or intestinal
parasites
– Urine dipstick & microscopy for albumin, sugar and blood
– Measurement of individual nutrient in body fluids (e.g. serum
retinol, serum iron, urinary iodine, vitamin D)
– Detection of abnormal amount of metabolites in the urine (e.g.
urinary creatinine/hydroxyproline ratio)
– Analysis of hair, nails & skin for micro-nutrients.

16. • Functional tests – assesses specific nutrient
dependent functions or functional
consequence of a specific nutrient.
– Activity of nutrient dependent enzymes (Flavin
Adenine Dehydrogenase dependent on riboflavin)
– papillory and visual threshold for Vit A, taste
acuity for Zinc

17. • Advantage
– It is useful in detecting early changes in body metabolism
& nutrition before the appearance of overt clinical signs.
– It is precise, accurate and reproducible.
– Useful to validate data obtained from dietary methods e.g.
comparing salt intake with 24-hour urinary excretion.
• Limitations
– Time consuming
– Expensive
– They cannot be applied on large scale
– Needs trained personnel & facilities

18. Clinical methods
• To detect signs and symptoms done by
physical examination or taking medical history.
Clinical manifestation happens at advanced
stages.

19. Hair
Protein, zinc, biotin
deficiency
Spare & thin
Protein deficiency
Easy to pull out
Vit C & Vit A
deficiency
Corkscrew
Coiled hair

20. Mouth
Riboflavin, niacin, folic acid,
B12 , pr.
Glossitis
Vit. C,A, K, folic acid & niacin
Bleeding & spongy gums
B 2,6,& niacin
Angular stomatitis, cheilosis
& fissured tongue
Vit.A,B12, B-complex, folic acid
& niacin
leukoplakia
Vit B12,6,c, niacin ,folic acid &
iron
Sore mouth & tongue

21. Eyes
Vitamin A deficiency
Night blindness,
exophthalmia
Vit B2 & vit A
deficiencies
Photophobia-blurring,
conjunctival
inflammation

22. Anthropometric methods
• Anthropometric measurements of human body
reflect changes in morphological variation due to
inappropriate food intake or malnutrition.
• Physical dimension of body and gross body
composition. E.g Ht, Wt, Body circumference and
indexes such as BMI, Wt/Age, Ht/Age, Wt/Ht.
• Helps in assessing moderate and severe
malnutrition. Chronic situations. Nutritional
history. Quick and inexpensive

23. Body weight
• Widely used
• Simplest and sensitive
• Indicates body mass
• Reflects more recent nutrition than does
height
• Serial measurement of weight (growth
monitoring) are more sensitive indicators of
changes in nutritional status than a single
measurement at a point of time

24. Height
• Influenced by both genetic and environmental
factors (nutrition and morbidity)
• Affected by long term nutritional deprivation,
index of chronic long duration malnutrition
Mid-Upper Arm Circumference (MUAC)
• Indicate the status of muscle development
• Determines not only malnutrition but also
mortality risk

25. • Advantages
– Objective with high specificity & sensitivity
– Measures many variables of nutritional significance (Ht, Wt, MAC, HC,
skin fold thickness, waist & hip ratio & BMI).
– Readings are numerical & gradable on standard growth charts, hence
reproducible.
– Non-expensive & need minimal training
• Limitations
– Inter-observers errors in measurement
– Limited nutritional diagnosis
– Problems with reference standards, i.e. local versus
international standards.
– Arbitrary statistical cut-off levels for what considered as
abnormal values.

26. Vital health statistics
• Infant mortality
• Under-5 mortality
• Total fertility rate

27. Types of assessments
• Survey
• Surveillance
• Screening
• Interventions

28. Indices
• Indices are continuous variables.
• It combines more than one measurements
• Usually evaluated at population level by
comparison with pre-determined cut-offs

29. • Iodine deficiency – Defined as Total Goiter
Rate of over 5% in school children
• Nutritional deficiency – food intake below the
Estimated Average Requirement
• Global hungry index
• Body Mass Index – Indicator of body
composition and overweight