Vitamin A
vitaminA fat-soluble vitamin essential for vision, immune function, and skin health.
Definition
A fat-soluble vitamin essential for vision, immune function, and skin health. Found as retinol in animal foods and as beta-carotene (provitamin A) in plant foods. DV is 900mcg RAE.
What Is Vitamin A?
Vitamin A is a fat-soluble vitamin that exists in two principal dietary forms: preformed vitamin A (retinol and its esterified form, retinyl ester), found in animal-source foods, and provitamin A carotenoids (most notably beta-carotene), found in plant foods. Both forms are converted in the body to retinal and retinoic acid, the biologically active metabolites.
The Recommended Dietary Allowance (RDA) for adults is 900 mcg RAE per day for men and 700 mcg RAE per day for women (RAE = retinol activity equivalents). The Daily Value (DV) used on US nutrition labels is 900 mcg RAE.
Key Functions
- Vision: Retinal is a component of rhodopsin, the light-sensitive protein in rod cells. Deficiency impairs night vision and can progress to xerophthalmia (dry eye) and blindness.
- Immune function: Supports the integrity of epithelial barriers (skin, gut, respiratory tract) and the proliferation and differentiation of immune cells.
- Cell growth and differentiation: Retinoic acid regulates gene expression involved in embryonic development and tissue maintenance.
- Reproduction: Required for normal sperm production and fetal development.
Food Sources
| Food | Approx. Vitamin A (mcg RAE per serving) |
|---|---|
| Beef liver (85 g) | 6,582 |
| Sweet potato (1 medium, baked) | 961 |
| Spinach (1/2 cup, cooked) | 573 |
| Carrots (1/2 cup, raw) | 459 |
| Whole milk (240 mL) | 112 |
Carotenoids from plant sources are converted to retinol less efficiently than preformed vitamin A; the conversion ratio for beta-carotene in food is approximately 12:1 by weight. Fat in the same meal enhances absorption of carotenoids.
Top Food Sources
| # | Food | Amount per 100g | % DV |
|---|---|---|---|
| 1 | （動物油脂類） たらのあぶら | 37000mcg | 4111% |
| 2 | Fish oil, cod liver | 30000mcg | 3333% |
| 3 | Beef, New Zealand, imported, variety meats and by-products, liver, raw | 28300mcg | 3144% |
| 4 | Veal, variety meats and by-products, liver, cooked, braised | 21100mcg | 2344% |
| 5 | Beef, New Zealand, imported, variety meats and by-products liver, cooked, boiled | 21000mcg | 2333% |
| 6 | Veal, variety meats and by-products, liver, cooked, pan-fried | 20100mcg | 2233% |
| 7 | Lamb, New Zealand, imported, liver, cooked, soaked and fried | 19900mcg | 2211% |
| 8 | ＜畜肉類＞ ぶた ［その他］ スモークレバー | 17000mcg | 1889% |
| 9 | Lamb, New Zealand, imported, liver, raw | 15400mcg | 1711% |
| 10 | ＜鳥肉類＞ にわとり ［副品目］ 肝臓 生 | 14000mcg | 1556% |
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