Antioxidants are chemicals that interact with and neutralize free radicals, they’re known as “free radical scavengers.” Free radicals are formed naturally in the body and have the potential to harm cells. At high concentrations, free radicals can be hazardous to the body and damage cells, including damage to DNA, which may relate to the development of cancer and other health conditions.
The body makes some of the antioxidants that it uses to neutralize free radicals. These antioxidants are called endogenous antioxidants. However, the body relies on external (exogenous) sources, primarily the diet, to obtain the rest of the antioxidants it needs. These exogenous antioxidants are commonly called dietary antioxidants. Fruits, vegetables, and grains are rich sources of dietary antioxidants. Some dietary antioxidants are also available as dietary supplements.
Since antioxidants neutralize free radicals, and free radicals may relate to the development of cancer, does it mean antioxidants have an effect of cancer prevention?
Among all the studies, randomized controlled clinical trials are considered to provide the most reliable evidence of the effect of a health-related intervention. To date, nine randomized controlled trials of dietary antioxidant supplements for cancer prevention have been conducted worldwide, according to National Cancer Institute. The antioxidants used are beta-carotene, alpha-tocopherol(vitamin E), selenium, retinol(vitamin A), aspirin, and vitamin C.
Overall, the nine clinical trials did not provide evidence that dietary antioxidant supplements are beneficial in primary cancer prevention. However, some of the clinical trials showed that taking antioxidant supplements may raise the risk of certain cancers. For example:
In the Alpha-Tocopherol/Beta-Carotene Cancer Prevention Study (ATBC), Finland, the study used Alpha-tocopherol (50 mg per day) and/or beta-carotene (20 mg per day) supplements for 5 to 8 years on middle-aged male smokers, the initial result showed increased incidence of lung cancer for those who took beta-carotene supplements.
In the Carotene and Retinol Efficacy Trial (CARET), United States, the study used 15 mg beta-carotene and 25,000 International Units (IU) retinol on people with smoking history, the initial result showed increased risk of lung cancer and increased death from all causes.
In the Supplémentation en Vitamines et Minéraux Antioxydants (SU.VI.MAX) Study, France, the study used vitamin C (120 mg), vitamin E (30 mg), beta-carotene (6 mg), and the minerals selenium (100 µg) and zinc (20 mg) for a median of 7.5 years on men and women, the initial result showed lower total cancer and prostate cancer incidence and all-cause mortality among men only, and increased incidence of skin cancer among women only.
There are more studies to go on the way of revealing the connection between antioxidants and cancer prevention, however, the current recommendation is to get antioxidants from diet, adding more fruits, vegetables and grains in your menu.