A review of the literature revealed that individuals with high alcohol intake, pre-existing liver disease, hyperlipidemia, or severe protein malnutrition may be distinctly susceptible to the adverse effects of excess preformed vitamin A intake (Ellis ct al., 1986; Hathcock ct al., 1990; Leo and Licber, 1999). These individuals may not be protected by the UL for vitamin A for the general population.
Based on data from the Third National Health and Nutrition Survey (NHANES III), the highest median intake of preformed vitamin A for any gender and life stage group was 895 ytg/day (Appendix Table C-6). This intake was being consumed by lactating women. The highest reported intake at the ninety-fifth percentile was 1,503 ytg/day in lactating women. For adult Americans who take supplements containing vitamin A, intakes at the ninety-fifth percentile ranged from approximately 1,500 to 3,000 yig/day (Appendix Table C-9). Less than 5 percent of pregnant women had dietary and supplemental intake levels exceeding the UL.
The risk of exceeding the UL for vitamin A appears to be small based on the intakes cited above. There is not a large difference between the UL for infants (600 yig/day) and the Adequate Intake for older infants (500 ytg/day). There is a body of evidence supporting the reversibility of bulging fontanels following the elimination of intermittent supplementation (dc Francisco ct al., 1993) or chronic, ingestion (Na/. and Edwards, 1952; Pcrsson ct al., 1965; Woodard ct al., 1961) of high doses of vitamin A.
The UL is based on healthy populations in developed countries. Supplemental doses exceeding the UL for vitamin A (60 to 120 mg) arc currently used in fortification and supplementation programs for the prevention and treatment of vitamin A deficiency, especially in developing countries. The UL is not meant to apply to communities of malnourished individuals receiving vitamin A prophylactically, either periodically or through fortification, as a means to prevent
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vitamin A dcficicncy or for individuals being treated for diseases, such as retinitis pigmentosa, with vitamin A.
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