Effect of season on vitamin a intake and validity of the simplified dietary assessment (SDA) method

Previously we have demonstrated the simplified dietary assessment (SDA) to be an accurate, noninvasive method to characterize the risk of vitamin A deficiency in different villages. Because in many regions vitamin A deficiency varies with season, we designed a study to assess the effect of season on nutrient intake as well as the performance of the SDA in a single community. Intake of vitamin A-containing food was significantly less in the dry season compared to rainy season as assessed by the two components of the SDA (CI p < 0.003; UPF p < 0.0001, respectively). While the summary SDA score correlated with retinol and nightblindness prevalence criteria in the dry season in the identification of vitamin A deficiency, it substantially underestimated the vitamin A deficiency risk during the rainy season. Of potential relevance was that fat intake, but not protein intake, was extremely low (mean < 9 g per child per day, or less than a third of recommended intake) in our study population. We conclude that provitamin A intake as well as the accuracy of the SDA exhibited seasonal variation. These results emphasize the need for further investigation into possible confounding variables (low fat intake, diarrheal disease and other infections, among others) that influence vitamin A status independent of provitamin A intake, and which are likely to effect the accuracy of the SDA and other dietary methodologies proposed to assess risk of vitamin A deficiency.