Life Extension is a global authority on health, wellness and nutrition

Vitamin A (retinol) is a yellow, fat-soluble, generic term for a large number of related compounds obtained from some carotenoids by conversion in the liver, its storage organ. Retinol (an alcohol) and retinal (an aldehyde) are often referred to as preformed vitamin A. While carotenoids are widely distributed in such foods as green and yellow vegetables, retinol is not found in any vegetable sources, but is concentrated in egg yolks and the livers of many animals. Vitamin A, either from animal sources or synthesized in our own liver, is essential for growth and reproduction, maintaining healthy vision, and supporting protein synthesis and cell differentiation.*

Vitamin A and its analogs have shown the ability to help maintain proper DNA function.67-70 One study, however, has shown that for certain lifestyles (e.g., smokers) supplemental intake of too much beta-carotene in the absence of other carotenoids and antioxidants (such as at least 400 IU/day of vitamin E) may be harmful.71

Anyone taking very high doses of vitamin A should do so under the care of a physician.

Levels of > 10,000-25,000 IU/day may cause congenital deformity, fatigue, headache, mouth fissures, and increased pressure on the brain. Should be used with serum levels as guidance, and never during pregnancy.