Vitamin A

Vitamin A is the name for a group of retinoids and carotenoids that are important for healthy skin, teeth, bones, and—as you might already know—eyes. Eating carrots for your eyesight isn't just an old wives' tale; vitamin A is truly necessary for good eyesight, especially when it comes to seeing in the dark. In fact, one sign of vitamin A deficiency is night blindness.¹ Vitamin A is also important for growth and development as well as for a properly functioning immune system.²

Retinoids are called preformed vitamin A because they are active forms of the vitamin that the body can use immediately. Meat, eggs, and dairy products provide preformed vitamin A. 

Carotenoids (including the well-known antioxidant beta-carotene) are known as provitamin A because the body must convert them into retinol (one of the active forms of vitamin A) before it can use them. Food sources of carotenoids include leafy greens, carrots, sweet potatoes, bell peppers, apricots, and grapefruit. Carotenoids are responsible for the bright colors of these fruits and vegetables.³

The different types of vitamin A have led scientists to give the recommendation for daily vitamin A consumption in micrograms of RAE (retinol activity equivalents) to account for the body's conversion of carotenoids into usable retinol.² For example, it takes 12 mcg of beta-carotene or 24 mcg of other carotenoids from food to produce 1 mcg of retinol that the body can actually use. The daily recommendation for adult women is 700 mcg RAE, for men 900 mcg RAE. On food packaging, however, vitamin A is still given in IU (international units). 1 IU retinol is equivalent to 0.3 mcg RAE, 1 IU beta-carotene from food is equivalent to 0.05 mcg RAE, and 1 IU of other carotenoids from food is equivalent to 0.025 mcg RAE.

Vitamin A deficiency is rare in developed countries. ⁴ Be careful with supplements (which can contain different ratios of preformed vitamin A and provitamin A) as too much vitamin A can lead to vitamin A toxicity.¹

Vitamin A rich Foods

Sources

1. The Linus Pauling Institute Micronutrient Information Center - Vitamin A
2. National Institutes of Health Office of Dietary Supplements - Vitamin A
3. MedlinePlus - Vitamin A
4. Medical News Today - What is vitamin A? What does vitamin A do?