INTRODUCTIONVitamin A is an important micronutrient comprising several retinoids: retinol, retinoic acid, and retinol esters. Its biological activities encompass effects on epithelial integrity and gene transcription, and there is considerable evidence that vitamin A supplementation has important bene®ts for children in the tropics. 1±3 The Zambian population is at high risk of vitamin A de®ciency as demonstrated by low serum retinol concentrations in 20% of adults living in Ndola (E. Kafwembe, unpubl. obs.). The HIV epidemic has had a severe impact on the Zambian population,
SUMMARYBackground: We have previously demonstrated a strong relationship between low serum retinol concentration and mortality in Zambian AIDS patients with diarrhoea, but were unable to detect any bene®t from oral micronutrient supplementation. Aim: To test the hypothesis that this is related to impaired availability of vitamin A, we analysed serum retinol concentration changes over 6 h following oral mega-dose therapy (60, 120 or 180 mg retinol). Methods: Twenty-four men without diarrhoea, 15 adults with persistent diarrhoea and 11 children (six girls, ®ve boys) with persistent diarrhoea were studied. Results: Men with persistent diarrhoea had lower baseline serum retinol concentrations (median 0.39 lmol/L, interquartile range 0.21±0.56) than controls (median 1.16 lmol/L, interquartile range 0.84±1.47; P 0.0003). After 60 mg retinol, the rise in serum retinol in HIV seropositive controls (median 0.63 lmol/L, interquartile range 0.35±0.77) did not