Vitamin A

What is Vitamin A?

Vitamin A (scientific name: retinol) is a fat-soluble vitamin. Humans can synthesize this vitamin themselves, from beta-carotene also called provitamin A. But this conversion is laborious (less than 10% on average), and proper conversion depends on several factors such as personal needs, the presence of certain enzymes, intestinal health, bile production and the amount of dietary fat in the intestines.

Direct intake of is therefore important for most people. The problem, however, is that vitamin A can only be found in animal products. Vegans or vegetarians thus rely on intake of beta-carotene.

It was "discovered" in 1913 by 2 American scientists (McCollum and Davis) and in 1947 it was first synthesized by 2 Dutch scientists, (van Dorp and Arens). However, there are already medical and scientific descriptions from the 18th and 19th centuries linking vitamin A deficiencies with their consequences.

Today, vitamin A is an easily manufactured substance and is readily and cheaply available. However, this is not true in developing countries where shortages are still widespread. For an aid organization like Vitamin Angels, preventing vitamin A deficiency is still a spearhead activity.

Safety

Because vitamin A is fat-soluble, excessive intake can lead to poisoning. The safe upper limit is 3,000 micrograms. The Reference Intake (RI) is 800 micrograms. RI indicates how much an average adult needs. With beta-carotene, there is no danger of poisoning: the body does not convert more beta-carotene into vitamin A than is needed.

Food sources

Vitamin A is found mainly in liver, fatty fish and egg yolks. 100 grams of beef liver contains a very high dose, about 36000 micrograms. 100 grams of smoked eel contains about 1400 micrograms. So with beef liver you have to be careful and definitely do not eat it every day.

Betacarotene is found in colored vegetables, sweet potatoes, green leafy vegetables, carrots, olives, tomatoes, apricots, squash, cress, parsley, kale and spinach.

Effects

The discovery of vitamin A was linked to research on the effects of deficiencies of this substance on the eyes. Still almost everyone knows it is good for the eyes (particularly adjusting vision at dusk and helping with dry eyes).

Less well known are its other functions: good resistance and healthy skin, hair and gums.

Immune system

Vitamin A plays a role in the formation of immune cells in the nose, lung tissue and gastrointestinal tract. These immune cells increase resistance to outside influences.

Skin, hair and gums

Vitamin A plays a role in the formation of certain skin cells that are important for skin health. These same cells are also found in hair and gums.

Explanation of dosage

The dosage of vitamin A products is sometimes a bit confusing. Some products use IE or IU (International Units/Units) in the naming, while others give the dosage in micrograms (mcg). Also, RAE* (retinol activity equivalent) is sometimes used. 1 RAE is equivalent to 1 microgram. The table below shows the relationship between dosing methods:

Other views also:

• Multivitamin
• Carotenoids
• Vitamin D
• Vitamin K2
• Pregnancy
• Vitamins