Too Much Vitamin A May Hurt, Not Help, Immunity
Vitamin A supplementation higher than normal levels can shut down the body's immunity, which may allow development of infections to which an individual would otherwise be immune. Study authors from the Radboud University Medical Center in Nijmegen, The Netherlands, stimulated immune cells from volunteers with vitamin A and saw that the cells produced fewer cytokines. These cells were also stimulated with other microbial structures, which resulted in long-term activation or training of the cells. In the presence of vitamin A, however, the microbial structures were not able to activate the immune cells.
Researchers emphasize that vitamin A supplementation should only be initiated with clear biological and clinical arguments. Findings from the study also suggest that low concentrations in certain situations may even be "normal."
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