Seasonal variations in vitamins A, C, riboflavin and folate intakes and status of pregnant and lactating women in a rural Gambian community: some possible implications

Abstract

Objective: To relate measured intake of vitamins A, C, folate and riboflavin to biochemical indicators of nutritional status for these micronutrients, and to examine seasonal variations.

Setting: MRC Dunn Nutrition Unit Field Station, Keneba, The Gambia, which has heavy rainfall in August, and little or no rain between late September and mid-June. Data were collected during 1978-80.

Subjects: Pregnant or lactating women in a rural farming community whose diet has been studied throughout the year.

Results: Mean daily intake of vitamin C varied from virtually nil during the rainy season to about 100 mg/d in May, while plasma ascorbate ranged from 0.2 to 1.2 mg/dl, and breast-milk ascorbate from 2 to 6 mg/dl, changing synchronously with changing intake. Intake of retinol equivalents ranged from 120 micrograms/d in December to 900 micrograms/d in June, and plasma carotenoids showed synchronous fluctuation from 60 to 180 micrograms/dl, whereas plasma retinol was virtually unchanged throughout the year at 30 micrograms/dl. Intake of riboflavin was very low throughout the year, but erythrocyte glutathione reductase activation coefficient ranged from a minimum of 1.5 in July to a maximum of 1.9 between December and March. Obstetric outcome also exhibited seasonal variation with lowest birthweights during the rainy season. Intakes of food energy are assumed to be the major dietary influence on birthweight, but micronutrient intakes and status may have additional effects, and seasonality clearly affects ascorbate intakes by suckling infants.

Conclusions: In countries such as The Gambia seasonality is a major determinant of micronutrient status. However, dietary intake is not the only factor which determines micronutrient status: thus there are seasonal fluctuations in riboflavin status which, for example, may relate to changes in the balance between energy intake and output, rather than to seasonal changes in riboflavin intake.