Retinol is a chemical form of vitamin A, a fat-soluble vitamin that you obtain from your diet, either as retinol or as one of several precursors called previtamin A carotenoids. Your body needs vitamin A for many critical functions and to keep several of your organs and systems operating at peak performance.
The term vitamin A is used to refer to a group of compounds called retinoids. These include retinol, one of the chemical forms of the vitamin that your body can use immediately when it is needed. Its name, retinol, refers to its essential role in your retina, where it becomes part of a visual pigment in light-sensitive cells that cause nerve impulses in your optic nerves, allowing you to see. Retinol also stimulates your body to make white blood cells, which are critical in helping you fight off infection, and it helps maintain the cells that line your blood vessels. It also has a general role in regulating cell division and in maintaining healthy bones.
In addition to its basic functions in your body, retinol may also help prevent or improve symptoms of several disorders. Research published in "Liver International" found that treatment of hepatitis C patients with a retinol-derived compound reduced the amount of virus in their bodies, compared to a placebo group. Retinol may also be useful in treating cases of eczema that are not responsive to usual therapies, according to a study in "British Journal of Dermatology" in which subjects with severe eczema who took a retinol-based compound had significant improvement of their condition compared to others given a placebo. Memorial Sloan-Kettering Cancer Center says that consuming retinol may also prevent recurring urinary tract infections and help treat parasitic infections and malaria.
According to the Office of Dietary Supplements, the recommended dietary amount, or RDA, of retinol for adult men and women is 900 and 700 micrograms, respectively. Pregnant women need somewhat more, about 770 micrograms; if you are breast-feeding, you need still more, about 1,300 micrograms daily. Amounts of vitamin A are often expressed as retinol activity equivalents, or RAEs; 1 microgram of pure retinol is equal to 1 RAE. In addition, vitamin A on food and supplement labels is often expressed in international units, or IUs, with 1 IU of retinol equal to 0.3 micrograms of retinol.
Foods especially rich in retinol include beef liver and sweet potatoes -- 3 ounces of liver provide more than 6,500 micrograms, while 1 sweet potato contains 1,400 micrograms. Fish are also good sources, with between 20 and 200 micrograms per 3 ounce-serving, depending on the type of fish. Eggs, dairy products such as cheese and milk and certain fruits and vegetables such as summer squash, mangoes, cantaloupe, carrots, broccoli and beans also provide retinol. In addition, certain processed foods such as breakfast cereals are fortified with vitamin A during their production. Retinol supplements are also available, either as part of a multi-vitamin or in separate form. However, because your body stores the compound in your liver, taking too many retinol supplements may be dangerous. The upper safe limit for retinol is about 3,000 micrograms daily for adults. Discuss these supplements in detail with your doctor before consuming them.