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Articles

Can Lack of Improvement in Vitamin A Status Indicators Be Explained by Little or No Overall Change in Vitamin A Status of Humans?¹

Department of Nutritional Sciences, University of Wisconsin at Madison, Madison, WI 53706

²To whom correspondence should be addressed. E-mail: sherry{at}nutrisci.wisc.edu.

Changes in vitamin A status using conventional indicators, i.e., serum and breast milk retinol concentrations and the modified relative dose response test, following a vitamin A intervention have not always been shown. A simplified model to predict calculated changes in vitamin A status after intervention is described. The model shows that changes in indicator values cannot be expected if the change in vitamin A status is only marginal. A critical review of several papers using vitamin A status assessment indicators was undertaken. Assumptions that included current knowledge concerning vitamin A absorption and metabolism were made and applied to the data. Based on current recommended daily allowances for women and children, one cannot necessarily expect a change in indicators if an overall change in vitamin A status was not achieved. Thus, when designing vitamin A intervention studies, the following parameters should be considered if applicable to the population to be enrolled in the study: average body weight, estimated liver weight, amount of vitamin A administered, estimated loss in breast milk and study duration.

KEY WORDS: • vitamin A • retinol • serum retinol • breast milk retinol • modified relative dose response.

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