@teleport.strength: Vitamin A is a fat-soluble nutrient that exists in two main dietary forms: (1) preformed vitamin A (retinoids retinol and retinyl esters) found in animal foods and supplements, and (2) provitamin A carotenoids (especially beta-carotene, plus alpha-carotene and beta-cryptoxanthin) found in colorful plants. In the body, retinol can be converted to retinal (key for vision) and retinoic acid (a hormone-like regulator of gene expression). Because it’s fat-soluble, absorption improves when vitamin A is eaten with dietary fat, and it’s stored primarily in the liver so deficiency develops slowly, but excess intake can accumulate. Core functions: • Vision: retinal forms photopigments (e.g., rhodopsin) that support low-light and color vision. • Immunity: supports epithelial barriers (skin, gut, airways) and helps regulate immune cells, affecting infection resistance. • Growth & development: retinoic acid guides cell differentiation; critical in pregnancy for fetal organ formation. • Skin & mucous membranes: supports normal keratinization, wound healing, and tissue repair. • Reproduction: involved in normal sperm production and embryonic development. Recommended intake and units: Vitamin A is reported as RAE (retinol activity equivalents) to account for different bioavailability. Typical adult RDAs are ~900 mcg RAE/day for men and ~700 mcg RAE/day for women (higher in pregnancy/lactation). The adult UL is 3,000 mcg RAE/day of preformed vitamin A (retinol/retinyl esters). Carotenoids from food aren’t strongly linked to toxicity, but very high supplemental beta-carotene has shown harm in some smoker populations. Deficiency: More common where diets lack animal foods and/or fat, or with malabsorption (celiac disease, IBD, pancreatic insufficiency, bariatric surgery). Early signs include night blindness and dry eyes; more advanced deficiency can cause xerophthalmia, corneal damage, rough/dry skin, impaired immunity, and slower recovery from illness. Toxicity: Chronic high preformed vitamin A intake can cause headache, nausea, dizziness, dry/peeling skin, hair loss, bone pain, liver injury, and increased fracture risk. Very high intakes in pregnancy can be teratogenic avoid high-dose retinol supplements unless medically directed. “Carotenemia” (orange skin tint) from high carotenoid intake is usually benign. Food sources: • Retinoids: liver (very high), egg yolk, dairy, fish oils. • Carotenoids: carrots, sweet potatoes, pumpkin, leafy greens, red/orange peppers, mango, cantaloupe. Tip: pair plant sources with a fat source (olive oil, avocado, nuts) to boost absorption. Performance angle: For athletes, vitamin A matters most for immune resilience, tissue repair, and maintaining healthy mucosal barriers during hard training, travel, or caloric deficits. Aim to meet needs through whole foods; be cautious with “megadose” retinol supplements, especially if you eat liver regularly. Interactions & supplementation: Absorption relies on normal fat digestion; zinc supports retinol transport (retinol-binding protein), and heavy alcohol use raises liver-toxicity risk. If you supplement, keep doses near the RDA unless supervised, and note whether the label lists retinol/retinyl palmitate (counts toward the UL) versus beta-carotene (provitamin). Assessment note: Blood “serum retinol” can drop during acute inflammation and may not perfectly reflect liver stores, so clinicians interpret it with symptoms, diet, and medical history. High-risk groups for low status include very low-fat diets, chronic GI issues, and post-bariatric clients; high-risk for excess include frequent liver intake plus retinol supplements.

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Thursday 26 February 2026 19:35:39 GMT