Vitamin A

What is vitamin A?

Vitamin A is an essential nutrient that supports healthy vision, immune function, and growth and development. It is a fat-soluble vitamin, meaning it requires fat to be absorbed, and it may be stored in the body for later use. Vitamin A exists in two major forms: preformed vitamin A and provitamin A. Preformed vitamin A is a group of compounds that includes retinol, retinal, retinoic acid, retinyl ester, and synthetic retinol.¹ Provitamin A (also known as carotenoids) is a group of pigments naturally found in plants. Examples of carotenoids include beta carotene, alpha carotene, and beta cryptoxanthin.¹ These carotenoids are converted into retinal in the body, meaning we can obtain vitamin A in either its preformed or provitamin form.²

Why we need it

One of vitamin A’s most notable functions is its role in vision. Vitamin A is required to produce rhodopsin, which is a pigment in our eyes that allows us to see in dark environments.¹ Additionally, vitamin A supports eye health through its antioxidant properties.³ In other words, vitamin A protects against oxidative stress, which is a phenomenon that can lead to cell damage and chronic disease. In this way, vitamin A may protect against age-related macular degeneration.³

Vitamin A also supports a healthy immune system. For example, vitamin A is essential for the growth and division of immune cells such as macrophages, dendritic cells, and regulatory B and T cells.⁴ Vitamin A also helps us produce mucus, which traps harmful bacteria and prevents illness or infection.⁴

Furthermore, vitamin A supports growth and development, reproductive processes, and bone health, among other things.⁵ Thus, vitamin A has many important functions that extend throughout the entire body.

Where it’s found

Vitamin A is found in many foods, in the form of either preformed vitamin A or carotenoids. Preformed vitamin A is present in animal-based foods such as meat, eggs, and dairy, as well as fortified cereals.² Carotenoids are present in brightly colored fruits and vegetables such as carrots, pumpkin, sweet potatoes, mango, and papaya, as well as dark leafy greens like spinach and kale.²

Vitamin A may also be taken as a supplement, either alone or as part of a multivitamin.

Daily requirements

The Recommended Dietary Allowance for vitamin A (i.e. the amount that is likely to meet the needs of most healthy people) is 900 micrograms (μg) per day for males aged 14 years and up, and 700 μg per day for females aged 14 years and up.⁶

These values are expressed in retinol activity equivalents (RAE), which is a standard unit of measure that accounts for the different forms of vitamin A.

Vitamin A deficiency

Vitamin A deficiency is a widespread health problem, especially in developing countries. In fact, vitamin A deficiency is the leading cause of preventable childhood blindness.⁵ Vitamin A deficiency can lead to xerophthalmia, a condition characterized by dryness of the eye and difficulty seeing in low-light conditions.^{2, 5} Vitamin A deficiency can have many other consequences as well, including impaired growth and development, bone issues, and increased risk of infection.¹

Fortunately, vitamin A deficiency can be prevented by consuming adequate amounts through food. While there is no minimum amount of vitamin A guaranteed to prevent deficiency, meeting the RDA for vitamin A can help ensure you are getting enough of this vitamin.

Can you get too much vitamin A?

Vitamin A can be toxic if consumed in excessive amounts. Symptoms of vitamin A toxicity include dry skin, headaches, nausea, loss of appetite, and bone pain.²

The Tolerable Upper Limit for vitamin A (i.e. the maximum amount that is considered safe for most people) is 2,800 μg per day for males and females aged 14-18 years, and 3,000 μg per day for males and females aged 19 and up.⁶ This amount refers only to preformed vitamin A, not carotenoids. This is because carotenoids are absorbed in lower amounts than preformed vitamin A, and your body can limit how much carotenoids are converted into preformed vitamin A.²

Fun facts

Since vitamin A plays an important role in cell growth and development, it may support healthy skin. For this reason, vitamin A (in the form of retinoids) is often added to skin creams, such as those used for acne or anti-aging purposes.⁷

Eating lots of brightly colored fruits and vegetables may actually cause your skin to turn a yellow-orange color! This is a condition known as carotenemia, which is due to excessive carotenoid consumption.³ Fortunately, this condition is harmless and can be fully reversed by eating less of these foods.³