Vitamin A is an essential micronutrient, and researchers see devastating consequences of vitamin A deficiency, especially in lower income countries, according to the report Global Prevalence of Vitamin A Deficiency in Populations at Risk 1995-2005 published by the World Health Organization (WHO).
So, what exactly is vitamin A? Why is it so important? Let’s explore this essential vitamin to find out.
What is vitamin A?
Vitamin A is a fat-soluble vitamin, so it dissolves best in lipids. It is stored in the liver, and can be found in two different forms: preformed vitamin A, found in animal products such as meat, poultry, fish, and dairy products; and provitamin A, found in plant-based foods (beta-carotene is the most common type of provitamin A). It is also available in dietary supplements.
What is the function of vitamin A in the body?
Vitamin A is essential to growth and development because it helps to form teeth, soft tissue, mucus membranes, and skin. It also produces the pigments in the retina, and promotes good vision, especially in low light. It supports healthy reproduction and boosts immune function.
In addition to these essential uses of vitamin A for body function, it also acts as an antioxidant. This means that vitamin A protects cells from free radicals—toxic substances in the body that wreak havoc on normal cell function and division—minimizing the risk of inflammatory disease and cancer.
How much vitamin A do I need?
According to the National Institutes of Health (NIH), the recommended daily intake of vitamin A is as follows:
- Age 0-6 months: 400 micrograms (mcg) of retinol activity equivalents (RAE)
- Age 7-12 months: 500 mcg
- Age 1-3 years: 300 mcg
- Age 4-8 years: 400 mcg
- Age 9-13 years: 600 mcg
- People aged 14 years and older: 700-900 mcg
- Breastfeeding women: 1,200-1,300 mcg
Is there such a thing as too much vitamin A?
Yes. According to the NIH, too much vitamin A can make you sick. It can also cause birth defects.
It should be noted that while hypervitaminosis A—or vitamin A toxicity—is possible from consuming too much preformed vitamin A (more than 1,500 mcg daily), it will not happen from consuming large amounts of carotenoids (like beta-carotene) in the form of fruits and vegetables. Too much carotenoids can, however, turn your skin a yellow or orange hue.
Chronic vitamin A toxicity is most common among people who take vitamin A dietary supplements which come in the form of preformed vitamin A. Chronic vitamin A toxicity occurs when too much vitamin A is taken over a long period of time, and it builds up in the body. This type of toxicity can cause liver damage and increased pressure in the brain. It can also affect your vision; cause bone pain; cause the skin to become dry, cracked, and flaky; and result in jaundice.
Acute vitamin A toxicity happens when a large amount of vitamin A is consumed over a short period of time. This can happen if a young child accidentally ingests supplements or multivitamins. Symptoms of acute vitamin A toxicity may include: drowsiness; irritability; abdominal pain; nausea and vomiting; and increased pressure on the brain.
Pregnant women should be especially careful not to ingest too much preformed vitamin A. Do not take more than the recommended dose of prenatal vitamins, even if you are deficient in one vitamin, or in iron. If you have deficiencies in other nutrients, take separate supplements for the specific ones you lack.
The Food and Nutrition Board (FNB) established tolerable upper intake levels of vitamin A, although it should be noted that ideally, a person should not have more than 1,500 mcg of preformed vitamin A, daily.
Tolerable Upper Intake Levels for vitamin A are as follows:
- Age 0-12 months: 600 mcg RAE [2,000 international units (IU)]
- Age 1-3 years: 600 mcg RAE (2,000 IU)
- Age 4-8 years: 900 mcg RAE (3,000 IU)
- Age 9-13 years: 1,700 mcg RAE (5,667 IU)
- Age 14-18 years: 2,800 mcg RAE (9,333 IU)
- Age 19+ years 3,000 mcg RAE (10,000 IU)
- Pregnancy and Lactation: 3,000 mcg RAE (10,000 IU)
Which foods are good sources of vitamin A?
According to the NIH, the following foods are among the best sources of vitamin A.
- Sweet potato- 1,403 mcg per serving
- Beef liver- 6,582 mcg per 3-ounce serving
- Spinach- 573 mcg per ½ cup, cooked
- Carrots- 459 mcg per ½ cup
Other good sources of vitamin A include cod liver oil, eggs, fortified cereals, fortified milk, orange and yellow fruits and vegetables, and dark leafy greens.
The best way to get the right amount of vitamin A and other nutrients is to eat a wide variety of fruits and vegetables— especially leafy greens— as well as fortified dairy products, legumes, and whole grains. You cannot eat too much beta-carotene, so you don’t have to worry about vitamin A toxicity from fruits and vegetables.
Can I get vitamin A toxicity from eating too many foods high in vitamin A?
It is only possible to get vitamin A toxicity from preformed vitamin A, also known as retinoids. This kind of vitamin A is found in animal sources and in supplements. It should also be noted that to get vitamin A toxicity solely from food sources, you would need to eat excessive amounts of animal liver every single day. Itt is quite rare for a person to experience vitamin A toxicity from food sources alone— most cases come from inappropriate supplement use.
According to research compiled by the NIH, you cannot get vitamin A toxicity—or it is nearly impossible to get vitamin A toxicity—from provitamin A, also known as carotenoids in the form of fruits and vegetables. The worst thing that could happen is that your skin will develop a yellow or orange hue.
What are the risks of vitamin A deficiency?
Vitamin A deficiency can cause vision problems, especially at night or in the dark. At first, a person may experience reversible night blindness which may lead to non-reversible corneal damage, also called xerophthalmia.
Vitamin A deficiency is rare in developed countries, but affects children and pregnant women in developing countries. A 2004 e-book called Comparative Quantification of Health Risks published by WHO reported that vitamin A deficiency affects 21.1% of preschool-age children and 5.6% of pregnant women worldwide.
Since vitamin A is important for immune health, vitamin A deficiency increases risk of mortality due to measles, diarrhea, malaria, and other infectious diseases. It is estimated that nearly 800,000 deaths worldwide can be attributed to vitamin A deficiency.
What are the symptoms of vitamin A deficiency?
According to the MSD Manual, vitamin A deficiency exhibits the following signs and symptoms:
Impaired dark adaptation (night blindness)
Xerophthalmia: drying and thickening of the conjunctivae and corneas
Bitot spots: foamy patches of epithelial debris and secretions on the exposed bulbar conjunctiva
Keratomalacia: the cornea becomes hazy and develops erosions, leading to its destruction
Keratinization of the skin and mucous membrane in the respiratory, GI, and urinary tracts. The skin will become dry, scaly, and thick. When this happens on the inner organs, it can cause respiratory infections.
The younger the patient, the more severe the effects of vitamin A deficiency. Long-term and severe deficiency can lead to growth problems and infections.
Who is at risk for vitamin A deficiency?
Young children and pregnant women who live in developing countries—where dietary intake of vitamin A-rich foods is chronically lower than required—are most at risk for vitamin A deficiency. It is especially common in countries of South Asia and Africa.
According to Comparative Quantification of Health Risks, common illnesses in these countries are associated with malabsorption and increased vitamin A excretion rates, which further increases the risk of vitamin A deficiency.
How is vitamin A deficiency treated?
Traditionally, vitamin A deficiency is treated with vitamin A palmitate oil, 60,000 IU orally per day for two days, followed by 45,000 IU orally once a day. The dose is adapted based on the age and weight of the patient, as well as their general health condition.
Since vitamin A can shorten the duration of the measles, and is usually a risk factor in severe cases of the measles, the WHO recommends that all children with measles in developing countries be given 2 doses of vitamin A supplements, 24 hours apart.
Vitamin A in medications
If you’ve heard of retinol because you’re using a skin cream or acne treatment in which retinol is the main player, you’re applying vitamin A to your skin— probably daily. Retinol, also known as vitamin A1, is sometimes used in creams to prevent pimples, blemishes, and wrinkles. It is sold as an anti-aging product.
If you’re using a retinol cream, avoid taking an oral supplement which also contains vitamin A. This can lead to vitamin A toxicity.
Always consult with your doctor before starting a new treatment, even if the product is available over-the-counter.
Should I take a vitamin A supplement?
The short answer is, probably not. You should not worry about vitamin A deficiency if you eat a balanced diet and do not have a malabsorption condition. Eat plenty of fresh produce including dark, leafy greens and yellow and orange fruits and vegetables, as well as fortified dairy products and cereal. For further questions on your specific case, and whether you should be taking nutritional supplement, consult your doctor.