Vitamin A
What is it: Vitamin A is a term used to include a group of fat-soluble compounds called retinol, retinal, and retinyl esters. Fat-soluble means the body can store vitamin A in the tissue for later use, in this case the liver houses any excess vitamin A in the body. The most common forms of vitamin A in food are the retinol and retinyl esters form which must be converted to retinal or retinoic acid, which are the active forms your body needs to benefit from this vitamin. Vitamin A comes in two forms.
- Preformed Vitamin A - active form of the vitamin found in animal products
- Provitamin A Carotenoids - alpha-carotene, beta-carotene and beta-cryptoxanthin — are the inactive form of the vitamin found in plants.
Functions/Benefits: The body can use preformed vitamin A as it is, and it will convert the provitamin A Carotenoids into the active form in our bodies. Vitamin A has various health benefits. These include supporting healthy vision, regular immune function, cellular growth as well as fetal development. It's also known for it's benefits to surface tissue like skin. The support of cellular growth is especially interesting with some studies showing that healthy consumption of vitamin A from plant based foods may result in lower risk of certain cancers.
Food Sources: Vitamin A in can be found in some of the following plants: Sweet potato, carrots, spinach, kale, cabbage, cantaloupe and many more. As well as in some meat products: beef liver, milk, egg yolks, butter, chicken liver, salmon etc.
Deficiency/Toxicity: According to the WHO, vitamin A deficiency is the leading cause of childhood blindness world wide. Yet in developed countries like the U.S, it is rare to develop a vitamin A deficiency. Vitamin A deficiency can result in mild symptoms like skin issues to more drastic symptoms like issues during pregnancy and blindness.
Because vitamin A is fat-soluble and can be sored in our body for later use, it is possible to get too much. The upper limit (UL) is set at of 10,000 IU (3,000 mcg) for adults to prevent toxicity. In order to develop a toxic level, one would have to ingest excessively high doses of vitamin A. If it does develop, it's called hypervitamosis A and can lead to a list of symptoms including hair loss, liver damage, dry skin and various others.
When taking a supplement with vitamin A, it's recommended to look for vitamin A in the form of beta carotene and not the preformed vitamin A found in animal products. This is due to the preformed version being toxic at high doses according to the Harvard Medical School, Special Health Report.
Fun Factoid: In 1939 when the Germans would bomb the British at night during World War II, the British Ministry of Information had a sneaky plan. They wanted to keep it a secret from the Germans that they had developed an on-board Airborne Intercept Radar system, so to avoid this leaking to the Germans, they told newspapers that the nighttime defensive success of Royal Air Force pilots was due to a diet where they ate a ton of carrots. They propagated the myth that carrots enable people to see better in the dark because of the beta-carotene or vitamin A they contained.
| Life Stage | Recommended Amount |
|---|---|
| Birth to 6 months | 400 mcg RAE |
| Infants 7–12 months | 500 mcg RAE |
| Children 1–3 years | 300 mcg RAE |
| Children 4–8 years | 400 mcg RAE |
| Children 9–13 years | 600 mcg RAE |
| Teen boys 14–18 years | 900 mcg RAE |
| Teen girls 14–18 years | 700 mcg RAE |
| Adult men | 900 mcg RAE |
| Adult women | 700 mcg RAE |
| Pregnant teens | 750 mcg RAE |
| Pregnant women | 770 mcg RAE |
| Breastfeeding teens | 1,200 mcg RAE |
| Breastfeeding women | 1,300 mcg RAE |
*RAE = retinol activity equivalents
Below are sources and further studies to review on vitamin A.
6 Health Benefits of Vitamin A, Backed by Science
Vitamin A: Benefits, Deficiency, Toxicity and More
Vitamin A Fact Sheet For Health Professionals
Vitamin A Fact Sheet for Consumers
What is Vitamin A and Why Do We Need It?