- Vitamin A is a generic term for a large number of related compounds that promote healthy vision, bone growth, and the surface linings of the skin. It helps the immune system by creating the white blood cells that destroys harmful bacteria and viruses.
- Vitamin A from animal sources is preformed and is absorbed as retinal. Vitamin A from plant sources are called carotenoids and are converted by our bodies into retinal.
- One of the first signs of vitamin A deficiency is night blindness. Severe deficiencies are not common in the United States but it can be found in individuals consuming excess alcohol, children living in poverty, and individuals with disorders of the intestines.
- Preformed Vitamin A at high levels can make you sick, cause birth defects, or death. It is possible to get too much vitamin A from eating large amounts of liver but in most cases toxicity is caused by taking excessive amounts of a preformed vitamin A supplement. Plant sources of vitamin A are not
toxic even at high levels.
- Recommended Dietary Allowances for vitamin A are measured in micrograms but most food and supplement labels use International Units (IU). Adequate Intakes (AI) are used when there is not enough evidence to establish an RDA. Tolerable Upper Intake Level (UL) applies to healthy populations and is designed to prevent vitamin A toxicity.
- A ½ cup of cooked vegetable provides more vitamin A than a ½ cup of the same vegetable raw because the cooked vegetable weighs more.