Vitamin Deficiencies in Rice-Eating Populations Effects of B-Vitamin Supplements

Summary

Rice is the staple food in many countries of Asia. Recent nutrition surveys in eight states, conducted by the National Nutrition Monitoring Bureau of India, show that though the average energy intake is adequate, more than 50% of the households surveyed consumed less than the Recommended Dietary Allowance (RDA) of energy. These households generally had per capita incomes of less than Rupees 2/- (US$ 0.25) per day. The average intake of vitamin A was only 42% of the RDA and that of riboflavin, 70% of the RDA. The average intake of other nutrients such as thiamin, niacin, ascorbic acid, iron and calcium was adequate, although thiamin deficiency was present in populations where rice was the main cereal, but not in populations that consumed mixed cereal or cereal-millet diets. The magnitude of the riboflavin deficiency (after correction for energy) was also more marked in the former. Vitamin A intake was not related to the type of cereal, but had some relationship to the quantity of vegetables consumed.

Nutrition surveys from Japan also reveal deficiencies in intake of energy, vitamin A, thiamin and riboflavin. The Japanese diet tends to be deficient by 20% in vitamin A and riboflavin, but not thiamin. Thus-, vitamin A, riboflavin and energy (in that order) are the major nutritional constraints in rice-eating populations.

Clear-cut correlations between the magnitude of dietary deficiency and the prevalence of signs and symptoms of vitamin deficiency were not apparent in the comparisons between populations, suggesting that as well as dietary deficiency other environmental factors play a role in the development of clinical deficiency. Attempts to correlate clinical deficiency with the magnitude of biochemical deficiency have also failed.

Recent studies aimed at examining the effects of food supplements (rural Gambian women) or vitamin supplements (rural Indian boys) on vitamin status suggest that in some communities, vitamin intakes close to the RDA fail to saturate the tissues, as judged by biochemical tests. In the Indian boys, there was a marked rise in urinary excretion of riboflavin during winter when the incidence of respiratory infections was high. Metabolic losses of vitamins due to infections may preclude tissue saturation despite adequate dietary intake. Administration for 1 year of B-vitamins at levels close to the RDA failed to reduce the prevalence of clinical deficiency signs, but did produce some improvement in hand steadiness — a psychomotor test. The data suggest that dietary improvement with regard to vitamins may fail to produce the desired impact on the health of some rural communities.