- Vitamin A is a fat-soluble nutrient essential for vision, immune function, cellular differentiation, and maintenance of epithelial tissues. It comes from the diet as preformed vitamin A in animal products and as provitamin A carotenoids in brightly colored fruits and vegetables. Because of its narrow safety margin, both deficiency and excessive intake can lead to adverse health effects.
- Vitamin A is widely available in over-the-counter formulations, including tablets, capsules, oral solutions, multivitamins, topical preparations, fish liver ingestion, and some poultry supplement. Although essential for health, excessive intake or accumulation, particularly in patients with . . .
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