So far the only consistent evidence of a connection between beta carotene and cancer is negative one. Beta carotene supplements may in fact increase the risk of certain types of cancer, particularly lung cancer in smokers. Researchers are still studying the possibility that the other carotenoids found naturally in fruits and vegetables may be more of a factor in lowering cancer risk than beta carotene. Overall, research does suggest that many health benefits can be gained from the vitamin A, of which beta carotene is a type, through a variety of foods.
Beta carotene is a type of vitamin A, a nutrient considered vital to the body’s development. Vitamin A can be obtained by consuming liver, egg yolks, diary products, and fish oils. Beta carotene is vitamin A which has been converted in the small intestine to retinol after eating foods such as squash, apricots and peaches, or carrots, broccoli and spinach.
Vitamin A and beta carotene are among the group of antioxidants, substances which may protect cells from damage caused by “free radicals.” Free radicals are molecules in the body responsible for the cell damage that can lead to cancer. Many foods that are orange in color are rich in beta carotene. These include pumpkin, mangoes, and cantaloupe. Green vegetables like spinach and kale also contain high amounts of beta carotene.
There has been a significant amount of research regarding beta carotene and cancer. Some studies have linked eating foods that are good sources of beta carotene or vitamin A with a lower risk of cancer. It is not definitively known if the lowered risk was exclusively due to the added vitamin A, or is because of other substances in the food, or a generally healthy diet. Studies conducted on animals showed that vitamin A and other retinoids, which strengthen the immune system, may shrink existing cancerous tumors or enhance certain cancer treatments.
Clinical trials involving beta carotene and cancer have found that lung cancer risk is not reduced with taking vitamin A supplements. In fact, it was found that using beta carotene supplements may even increase a smoker's risk of developing lung cancer. Results of studies on the effect of vitamin A on other forms of cancer have been inconsistent and inconclusive.
Most of the information available about any connection between beta carotene and cancer suggests that beta carotene alone may not be an effective tool of cancer prevention. Other carotenoids found in fruits and vegetables may be more important in protecting the body’s healthy cells. It would seem that all the different micronutrients found in a healthy diet of fruits, vegetables, grains, and legumes taken in combination may be a better defense against cancer than any individual vitamin supplements.