Dietary Assessment in PSM (Preventive and Social Medicine)

Dietary assessment is one component of a comprehensive nutritional assessment at both the individual and community level. The term "diet survey" is used in PSM to describe the methods employed for assessing food consumption.

Overview

The value of nutritional assessment is greatly enhanced when it is supplemented by an assessment of food consumption. Direct assessment of food consumption involves dietary surveys, which may be:

Household inquiries, or
Individual food consumption surveys

(Park's Textbook of PSM)

Methods of Dietary Survey

1. Weighment of Raw Foods

Most widely employed method in India
Considered practicable and fairly accurate if properly carried out
The survey team visits households and weighs all food going to be cooked and eaten, as well as food wasted or discarded
Duration: usually 7 days (called "one dietary cycle"), though it may range from 1 to 21 days
Advantage: captures food before cooking losses/additions

2. Weighment of Cooked Foods

Foods analyzed in the state in which they are normally consumed
More reflective of actual intake
Not easily acceptable among people (a practical limitation)

3. Oral Questionnaire Method

Useful for diet surveys of large numbers of people in a short time
Inquiries are made retrospectively about nature and quantity of foods eaten during the previous 24 or 48 hours
If properly carried out, can give reliable results
May also include data on dietary habits and practices

Analysis of Dietary Survey Data

Collected data must be translated into:

(a) Mean intake (grams) of food in terms of cereals, pulses, vegetables, fruits, milk, meat, fish, and eggs
(b) Mean intake of nutrients per adult man value or "consumption unit"

This exercise requires the use of food composition tables. In India, the standard reference is the ICMR publication: "Nutritive Value of Indian Foods".

What a Diet Survey Provides

A diet survey gives information about:

Dietary intake patterns
Specific foods consumed
Estimated nutrient intakes
Relative dietary inadequacies as judged by present standards

This data is valuable for:

Planning health education activities
Assessing the extent of changes needed in agriculture and food production industries

Indirect Method: Food Balance Sheet

An indirect method of dietary assessment (studied under ecological factors):

Food supplies are related to census population to derive levels of food consumption in terms of per capita supply availability
Refers to the country as a whole - conceals regional and socio-economic differences
Advantage: cheaper and simpler than direct assessment methods
Gives an indication of the general pattern of food consumption in the country

Ecological Factors in Dietary Assessment

A complete nutritional (dietary) assessment must also account for:

Factor	Details
Socio-economic factors	Family size, occupation, income, education, cultural patterns, feeding practices of children and mothers
Health and educational services	Primary health care, feeding programs, immunization
Conditioning influences	Parasitic, bacterial, and viral infections that precipitate malnutrition

An "ecological diagnosis" of all factors influencing nutrition in the community is necessary before preventive and control measures can be put into effect.

Nutritional Surveillance (Related Concept)

Defined as: "Keeping watch over nutrition, in order to make decisions that will lead to improvement in nutrition in populations" (WHO/FAO).

Three objectives:

Aid long-term planning in health and development
Provide input for programme management and evaluation
Give timely warning and intervention to prevent short-term food consumption crises

(Park's Textbook of PSM)

Summary Table of Diet Survey Methods

Method	Basis	Best Use	Limitation
Weighment of raw foods	Weigh pre-cooking	Household surveys in India	Labour-intensive
Weighment of cooked foods	Weigh cooked portion	Accurate actual intake	Poor acceptability
Oral questionnaire (24-hr recall)	Retrospective inquiry	Large population surveys	Recall bias
Food balance sheet (indirect)	National supply data	Country-level trends	Hides group variation

Sources: Park's Textbook of Preventive and Social Medicine (PSM) - Assessment of Dietary Intake, Section 5; Nutritional Surveillance section.

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