Vitamin A is an essential nutrient that humans require in small amounts for normal visual system function, immune system regulation, cell growth, reproduction, fetal development, and epithelial cellular integrity maintenance. One of vitamin A’s most well-known functions is its role in vision and eye health. The active form of vitamin A, retinal, combines with the protein opsin to form rhodopsin, the light-absorbing molecule necessary for both low-light and color vision. The cornea and conjunctiva are also protected and maintained by it. A large clinical trial found that taking a specific vitamin combination containing beta-carotene reduced the risk of developing age-related macular degeneration and vision loss by 25% in people at high risk.
Vitamin A also has antioxidant properties. Antioxidants are substances that fight free radicals that are produced by your body’s natural metabolic activities or by being exposed to smoking, alcohol, fried foods, and toxic chemicals such as pesticides and air pollution. These powerful compounds are effective at scavenging free radicals and may help to reduce inflammation in the body. Several studies in current and former smokers, as well as nonsmokers, discovered that higher intakes of carotenoids are associated with a lower risk of lung cancer. Lycopene, a carotenoid that gives fruits and vegetables a pink or red color, such as tomatoes, watermelons, and pink grapefruit, has been linked to a variety of health benefits ranging from improved heart health to cancer prevention. Epidemiologic studies indicate an inverse relationship between lycopene consumption and the risk of cancer, particularly prostate, stomach, lung, and hormone-positive breast cancer.
It is found naturally in foods and can also be obtained through supplements. In food, there are two types of vitamin A. Preformed vitamin A (retinol and retinyl esters) is found only in animal products such as liver, egg, dairy, and fish oil, whereas provitamin A carotenoids are abundant in plant foods such as fruits, vegetables, and oils. Both types of vitamin A must be converted by your body to retinal and retinoic acid, the active forms of the vitamin before they can be used.
Though vitamin A is commonly thought of as a single nutrient, it is the name for a group of fat-soluble compounds that includes retinal, retinol, and retinoic acid. The retina is essential for vision. Retinoic acid plays an important role in cell growth, differentiation, and organogenesis. Both retinal and retinol are stored in the body, but retinoic acid is not. Excessive vitamin A consumption over a long period can cause liver damage, partial loss of hair, cracked lips, dry skin, and birth defects in a fetus.
Vitamin A Sources
Preformed vitamin A is found exclusively in animal products, such liver, fish, egg, whole milk, and dairy products. Pro-vitamin A carotenoids are highest in green leafy vegetables, yellow vegetables, and yellow and orange noncitrus fruits (cantaloupe, mangoes, apricots, and papaya). Getting enough vitamin A from your diet should help you avoid deficiency symptoms such as night blindness, hair loss, dry eyes, and higher infection susceptibility.
Foods High in Vitamin A
| Food | Micrograms (mcg) RAE per 100 grams | Percent DV |
| Cod Liver Oil | 30,000 | 3,333% |
| Beef Liver | 9,442 | 1,049% |
| Lamb Liver | 7,491 | 832% |
| Bluefin Tuna | 757 | 84% |
| King Mackerel | 252 | 28% |
| Salmon | 149 | 17% |
| Butter | 684 | 76% |
| Goat Cheese | 407 | 45% |
| Boiled Egg | 149 | 17% |
| Sweet Potato | 1,043 | 116% |
| Carrot | 852 | 95% |
| Kale | 681 | 76% |
| Winter Squash | 558 | 62% |
| Spinach | 469 | 52% |
Vitamin A Recommended Intakes
The vitamin A intake recommendation is expressed in micrograms (mcg) of retinol activity equivalents (RAE) because only a portion of beta-carotene is converted to retinol by the body. One mcg RAE is equivalent to 1 mcg retinol, 2 mcg supplemental beta-carotene, 12 mcg dietary beta-carotene, or 24 mcg dietary alpha-carotene or beta-cryptoxanthin. The RDA for vitamin A is 900 mcg per day for adults males and 700 mcg per day for adults females. Any vitamin A that your body does not use right away is stored for later use. This implies that you do not require it daily.
Recommended Dietary Allowances (RDAs) for Vitamin A
| Age | Male | Female |
| 0–6 months | 400 mcg RAE | 400 mcg RAE |
| 7–12 months | 500 mcg RAE | 500 mcg RAE |
| 1–3 years | 300 mcg RAE | 300 mcg RAE |
| 4–8 years | 400 mcg RAE | 400 mcg RAE |
| 9–13 years | 600 mcg RAE | 600 mcg RAE |
| 14–18 years | 900 mcg RAE | 700 mcg RAE |
| 19–50 years | 900 mcg RAE | 700 mcg RAE |
| Plus 51 years | 900 mcg RAE | 700 mcg RAE |
Vitamin A Deficiency
A lack of vitamin A can result in night blindness (nyctalopia) and keratomalacia, the latter of which can lead to permanent blindness if not treated. It is most common in developing countries, usually as a result of malnutrition. Night blindness and extremely dry, rough skin may indicate a vitamin A deficiency. Other symptoms of vitamin A deficiency include decreased infection resistance, and slower bone growth.
The effects of vitamin A deficiency are more severe in younger patients. It can cause growth retardation, infections, and other serious health problems. In children with severe vitamin A deficiency, the mortality rate can exceed 50%. Vitamin A deficiency is the largest cause of preventable blindness in children globally, according to the World Health Organization, and it significantly increases the severity and risk of death from infections such as measles and diarrhea.
Vitamin A Toxicity
Toxic or excessive levels of vitamin A are a greater concern in the United States than deficiencies. Because vitamin A is fat-soluble, excess amounts are stored in the body, primarily in the liver, where they can accumulate. Although high levels of preformed vitamin A can be toxic, high levels of beta-carotene and other provitamins A carotenoids have not been linked to serious side effects. According to some studies, taking more than 1.5 mg (1,500 µg) of vitamin A per day for several years may alter your bones, making them more susceptible to fracture as you get older.
If you take vitamin A supplements, make sure your daily consumption of vitamin A from food and supplements does not exceed 1.5 mg. This is especially critical for older people, who are already at a higher risk of developing osteoporosis.