Purpose
The primary objectives include:
● Assessing the magnitude of nutritional problems.
● Identifying geographical distribution of these problems.
● Identifying populations at risk for specific nutritional deficiencies.
● Defining problems and formulating policies.
● Developing and evaluating health care programs that address identified needs.
● Informing long-term planning in health and development.
● Providing input for program management and evaluation.
● Offering timely warning and intervention to prevent short-term food consumption
crises.
Study Methods
Nutritional surveys can be cross-sectional (examining a sample at a single point in time to
determine prevalence) or longitudinal (following a group over time). These often involve
selecting random and representative samples from the community, encompassing all ages,
sexes, and socio-economic groups. Expert statistical advice is crucial for planning such surveys.
Techniques
A comprehensive assessment typically integrates multiple techniques.
- Clinical Examination
○ Methodology: Simple, direct, and inexpensive, relying on observation of physical
signs associated with malnutrition. Standard survey forms are used to minimize
subjective errors.
○ Limitations:
■ Primarily diagnoses clinically manifest cases.
■ Many findings are non-specific.
■ Generally requires a medical professional.
■ Malnutrition cannot be quantified solely by clinical signs.
■ Many deficiencies may not present with physical signs. - Anthropometry
○ Purpose: Valuable, widely used, inexpensive, and non-invasive indicators of
nutritional status, reflecting growth and development patterns over time.
○ Tools: Infantometers, scales (like the Salter scale for community use), weighing
machines, and Shakir’s tape. Harpenden calipers for skinfold thickness.
○ Indices (particularly for children under five):
■ Weight for age: Detects general undernutrition (underweight).
■ Height for age (or length for age): Indicates chronic malnutrition
(stunting).
■ Weight for height (or weight for length): Best estimate of acute
malnutrition severity (wasting) and is age-independent.
■ Mid-arm circumference (MAC): Remains relatively constant between
1-5 years. A MAC < 12.5 cm indicates severe malnutrition. The “bangle test” (4 cm diameter) can quickly assess MAC.
■ Skinfold thickness: Measures subcutaneous fat. Sums > 40mm in boys
and > 50mm in girls can indicate obesity. Main drawback is poor
repeatability. Mid-triceps is a single best measurement site.
■ Body Mass Index (BMI): Weight in kg / (height in meter)^2. Normal
range is 18.5-25.
■ Waist-to-hip ratio (WHR): High WHR (>0.9 in men and >0.85 in women)
indicates abdominal fat accumulation. - Diet Survey
○ Purpose: Directly observes what people are eating to identify inadequacies and
suggest remedies.
○ Methods:
■ Weighment of raw foods: Weighs all food before and after cooking,
typically over a 7-day “dietary cycle”. Considered accurate but
time-consuming.
■ Weighment of cooked foods: Less acceptable but more accurate as it
analyzes food in its consumed state.
■ Oral questionnaire method: Retrospective inquiry about food consumed
in the previous 24 or 48 hours. Useful for large numbers of people. The
“diet cycle” can also be used.
■ Inventory method: Estimates food stock for a week, suitable for
institutions like hostels.
○ Data Translation: Collected data is translated into mean intake of food groups
and nutrients (per consumption unit) using food composition tables. - Biochemistry
○ Purpose: More precise than clinical signs, measuring individual nutrient
concentrations in body fluids (e.g., serum retinol, serum iron) or detecting
abnormal metabolites (e.g., urinary iodine). Can reveal nutritional status in
preclinical stages.
○ Examples:
■ Hemoglobin estimation: Most important laboratory test, indicates overall
nutrition status and anemia.
■ Serum albumin: Best marker for protein nutritional status; >3.5 g/dl
satisfactory, <3 g/dl severe malnutrition.
■ Serum ferritin: <15 µg/dl indicates storage iron deficiency.
■ Serum transferrin saturation: <16% indicates iron deficiency anemia
(normally 33%).
■ Urinary iodine excretion, serum T3, T4, TSH, neonatal TSH levels:
Used for assessing iodine deficiency disorders (IDD) and monitoring
goitre control programs.
○ Limitations: Costly, time-consuming, cannot be applied on a large scale, often
done on subsamples. - Functional Assessment
○ Purpose: Measures physiological functions influenced by nutritional status.
○ Examples: Erythrocyte fragility (Vit. E, Se), capillary fragility (Vit. C), leucocyte
chemotaxis (P/E, Zn), prothrombin time (Vit. K), sperm count (Energy, Zn), dark
adaptation (Vit. A, Zn), and work capacity (P/E, Fe). - Vital and Health Statistics
○ Purpose: Analysis of mortality and morbidity data identifies high-risk groups and
indicates the extent of risk.
○ Indicators:
■ Infant Mortality Rate (IMR): Universally recognized indicator of child
health and social environment.
■ Mortality in 1-4 years age group: Particularly related to malnutrition in
developing countries.
■ Low birth weight (LBW) prevalence: Less than 2.5 kg. In India, 28% of
babies are born with LBW.
■ Morbidity data: From hospitals or community surveys (e.g., related to
PEM, anemia, or vitamin A deficiency) provides additional information. - Assessment of Ecological Factors (Ecological Studies)
○ Purpose: Malnutrition results from interacting ecological factors; collecting this
information completes the assessment.
○ Factors:
■ Food Balance Sheet: Indirectly assesses food consumption by relating
supplies to census population to derive per capita availability. Indicates
general food consumption patterns.
■ Socio-economic factors: Family size, occupation, income, education,
customs, and cultural patterns related to feeding practices.
■ Health and Educational Services: Presence of primary health care
(PHC) services, feeding, and immunization programs.
■ Conditioning Influences: Parasitic, bacterial, and viral infections that
can precipitate malnutrition.
Primary Steps
Before conducting a survey, essential preparatory steps include:
- Pretesting the format of data collection.
- Training staff for data collection.
- Supervision of the study.
Nutritional Surveillance
Definition: It is defined as “keeping watch over nutrition, in order to make decisions that will lead to improvement in nutrition in population“
● Strategy: Detection of malnutrition through nutritional surveys.
● Approach: Diagnostic-interventional.
● Sample: Typically uses representative samples of 50-100 individuals.
● Purpose: Helps to assess nutritional status over time and judge whether achievements
can be sustained.