Vitamin A

Article by Amy Bragagnini, MS, RD
Posted on May 14, 2008

A healthy diet should contain all of the important vitamins and minerals that are essential to our body. Vitamin A is just one example of a vitamin that plays a key role in vision, bone growth, and reproduction of cells that line any opening to the body (mouth, nose, lungs, stomach, etc). Vitamin A can also aid in functioning of skin and mucous membranes, which play an important role in protecting us from viruses and bacteria.

There are two categories for vitamin A: retinol (preformed vitamin A) and carotenes (provitamin A carotenoid). Retinol is the animal source of the vitamin and examples include liver, whole milk, and some fortified foods. Animal sources of vitamin A are more potent than the plant sources and may be toxic if ingested in large amounts. The carotenes are found in colorful fruits and vegetables. The orange/yellow fruits and vegetables contain increased amounts of vitamin A. Deficiency of vitamin A may lead to symptoms such as brittle nails, diarrhea, night blindness, and loss of sense of smell. If vitamin A rich foods are eaten in large quantities, then changes in skin color may be seen. For example, if carrots are eaten in large amounts, then a yellow/orange skin tint may be seen. High intake leads to a saturation of body stores, but is generally not considered dangerous to health.

Vitamin A is a nutrient that is essential in our body. It may be helpful in lowering risk of many types of cancer. However, a number of studies reviewed vitamin A and/or beta carotene supplements in regards to cancer prevention and positive results were not found. One study, reported in the Journal of the National Cancer Institute, December 1, 2004 reported “not only do beta-carotene supplements not prevent lung cancer in people at high risk for the disease, they appear to increase rates of the disease, particularly among smokers.” As with all of the vitamins and minerals, I advise that people obtain these from whole foods and a diet rich in whole grains, fruits and vegetables to maximize cancer fighting potential.