Antioxidants and Cancer Prevention : Antioxidants are substances that may prevent cellular damage caused by free radicals. Exposure to environmental factors such as radiation, tobacco smoking, etc cause free radical damage, which over time cancer. Some of the well-known antioxidants are vitamin A, C, E, lycopene, selenium and beta-carotene.
Though laboratory evidences suggest antioxidants may slow down the rate of development of cancer, large scale and randomized clinical trials in the 1990s have given mixed results. Such studies examined the effects of beta carotene and such other antioxidants in different groups of cancer patients belonging to different geographical locations.
In the first study in 1993, the combined effect of vitamin E, beta-carotene and selenium was tested on Chinese men and women with high risk of gastric cancer. The study showed significant positive result by bringing down gastric cancer and overall cancer incidence
In the second study in 1994, beta-carotene was found to increase the rate of lung cancer in Finnish male smokers significantly. But, vitamin E treatment showed no apparent effect on the rate of lung cancer.
Another trial conducted in 1994 examined the effect of beta-carotene and retinol (vitamin A) in lung cancer patients. The study showed a possible increase in lung cancer rate.
In 1996, Physicians Health Study (PHS) tested the effect of beta-carotene and aspirin among U.S. male physicians. It was found that beta-carotene and aspirin had no effect on the rate of development of cancer.
The last study in 1999 was conducted by Women’s Health Study (WHS) on women aged 45 years and above. The study examined the effect of beta-carotene and vitamin E in the prevention of cancer and cardiovascular disease. Healthy women showed no apparent benefit or harm from beta-carotene supplementation. Investigation regarding the effect of vitamin E is currently going on.
Following mixed results from different clinical trials, National Cancer Institute (NCI) will examine the long-term effects of beta-carotene among participants in these studies.