JULY 2007 NEWS

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VITAMIN A & BETA CAROTENE

     In ancient Egypt, many people knew that eating liver would help cure night blindness. What they didn’t know was that liver is a rich source of vitamin A. Vitamin A is a fat-soluble vitamin. Its most usable form is called retinol which is found mainly in animal foods like liver and eggs. Some plant foods contain substances called provitamin A carotenoids that can be converted to retinol. An example of a vitamin A precursor in vegetables is beta carotene, an orange pigment found in carrots, sweet potatoes, squash, mangoes, and other fruits and vegetables.  Beta carotene also doubles as an anti-oxidant which protects us from diseases. (Note that lycopene, lutein, and zeaxanthin are also carotenoids, but your body cannot convert them to vitamin A.)

     Vitamin A is important because it maintains vision, bone growth, reproductive health, and cell processes. It protects the surface linings of our eyes and our respiratory, urinary, and intestinal tracts. This protection helps prevent infections by fighting bacteria and viruses. In the eyes, vitamin A keeps the cornea clear and it helps convert light energy into nerve impulses at the retina. At the cellular level, vitamin A helps each cell’s differentiation process, which is how cells decide what function they’ll perform in the body. By maintaining the mucous membranes that protect the linings of our body systems, vitamin A keeps all of our systems healthy. Vitamin A is also critical for healthy bone development in children. Finally, vitamin A participates in sperm production in men and supports normal fetal development in pregnant women.

      In many parts of the world where malnutrition is widespread, vitamin A deficiencies are common. When our bodies are deficient in vitamin A, serious health problems can result. These include night blindness, dry eyes, corneal degeneration resulting in total blindness, impaired immunity, and white lumps at the base of hair follicles resulting in dry, rough and scaly skin (follicular hyperkeratosis). 

     Only a few foods naturally contain vitamin A. These include whole milk, whole eggs, fortified dairy products, and liver. Good sources of beta carotene (which converts to vitamin A in the body) include spinach, broccoli, and deep orange-colored fruits and vegetables. The World Health Organization has a mission to provide supplements of vitamin A to as many malnourished children as they can because they have found that when enough vitamin A is in a child’s diet, the chances of dying from pneumonia, measles, and other childhood infectious diseases are greatly reduced.

     Since vitamin A is fat-soluble, it can be stored in the body to be used when current vitamin A amounts decline. Because of this, people can get too much vitamin A and develop vitamin A toxicity which can result in dry, itchy skin, headache, fatigue, hair loss, loss of appetite, vomiting, and liver damage.

     Retin-A (also known as Renova or tretinoin), a prescription medication used to treat acne or wrinkles, is a derivative of vitamin A and should never be taken by pregnant and nursing women. It may also cause sensitivity to sunlight, wind, and cold. Accutane, another anti-acne drug, is also derived from vitamin A but is much more dangerous than Retin-A. Accutane causes birth defects when taken by pregnant women and can be very toxic to other people. 

     The upper limit for vitamin A supplementation in healthy people is 10,000 i.u. daily. Pregnant women should limit their intake of vitamin A to 8,000 i.u. to prevent birth defects in developing fetuses. Beta carotene can be supplemented safely in amounts of up to 25,000 i.u. each day. Taking too much beta carotene may actually turn your skin orange, but this is harmless and temporary and it goes away when consumption is reduced.

     While beta carotene has been shown to help prevent cancer, some studies suggest that smokers should not use beta carotene supplements. The research varies, however, so taking a cautious approach is recommended if you smoke. People who don’t eat animal products may benefit from taking beta carotene supplements as would people with certain diseases that interfere with vitamin A absorption.