Antioxidants – you find them in health drinks, nutritional supplements, anti-ageing skin creams and even in your morning cuppa. What exactly are antioxidants and can they cure the cancer?
Antioxidants are chemical compounds that can bind to free oxygen radicals preventing these radicals from damaging healthy cells. Berries, broccoli, tomatoes, red wine, whole grains, green vegetables, tea, coffee are examples of food items rich in antioxidants.
During normal cellular activities, various processes inside of cells produce reactive oxygen species (ROS). These compounds, when present in a high enough concentration, can damage cellular proteins, lipids or genetic material that may lead to cancer. The purpose of antioxidants in a physiological setting is to prevent ROS concentrations from reaching a high-enough level within a cell that damage may occur (1).
In early 2004, the National Cancer Institute (NCI) released a new fact sheet concerning cancer prevention and antioxidants (2). Considerable laboratory evidence from chemical, cell culture, and animal studies indicates that antioxidants may slow or possibly prevent the development of cancer. However, information from recent clinical trials is less clear. In recent years, large-scale, randomized clinical trials have not yielded conclusive evidence on whether antioxidants can prevent cancer. Thus the question arises whether we should include antioxidants in our diet to prevent cancer or can a patient be cured of cancer by popping antioxidant pills?
Arguments in favor
Recent trials suggest that antioxidants may prevent cancer (2):
The first large randomized trial on antioxidants and cancer risk was the Chinese Cancer Prevention Study, published in 1993. This trial investigated the effect of a combination of beta-carotene, vitamin E, and selenium on cancer in healthy Chinese men and women at high risk for gastric cancer. The study showed a combination of beta-carotene, vitamin E, and selenium significantly reduced incidence of both gastric cancer and cancer overall.
A 1994 cancer prevention study entitled the Alpha-Tocopherol (vitamin E)/ Beta-Carotene Cancer Prevention Study (ATBC) demonstrated that lung cancer rates of Finnish male smokers increased significantly with beta-carotene and were not affected by vitamin E.
A study carried out in Maryland, USA, revealed that, greater intake of fruits and vegetables was associated with lower risk of cancer and cardiovascular disease. These findings support the general health recommendation to consume multiple servings of fruits and vegetables (5–9/day) (3).
Tamoxifen, when combined with vitamin E, works better than either alone in breast cancer cell (4).
Arguments opposed
Antioxidants, commonly known to protect cells from the damage that makes them turn cancerous, may actually help cancerous cells survive, according to a study published online in Nature (5).
Red wine consumption is not associated with reduced risk of colorectal cancer which may dampen the hype about wine being a cure for cancer (6).
Although it is premature to use antioxidants for cancer therapy, the emerging evidence suggests that these agents may reverse tumor signaling mainly in preclinical models (i.e. not on humans) (7).
Consumption of antioxidant supplements in high-income countries has become widespread. It is estimated that about one-third of adults in high-income countries consume antioxidant supplements (8). Antioxidant supplements in pills are synthetic; factory processed, and may not be safe compared with their naturally occurring counterparts (9-12). In spite of intensive research, it is still not clear exactly which specific dietary constituents of fruits and vegetables might be beneficial. More research will be needed before we understand the complex relationship between cancer and antioxidants to translate the effects of antioxidants from the bench to the bedside. It thus may be concluded that one should think twice before spending a fortune on antioxidant supplements – a balanced diet rich in antioxidant-rich food may enough to keep cancer at bay.
References
1. Seifried HE, Anderson DE, Fisher EI, Milner JA. A review of the interaction among dietary antioxidants and reactive oxygen species. J Nutr Biochem. 2007; 18:567-79.
2. http://www.cancer.gov/cancertopics/factsheet/prevention/antioxidants
3. Genkinger JM, Platz EA, Hoffman SC, Comstock GW, Helzlsouer KJ. Am J Epidemiol. 2004; 160:1223-1233.
4. Gundimeda U, Chen ZH, Gopalakrishna R.Tamoxifen Modulates Protein Kinase C via oxidative stress in estrogen receptor-negative breast cancer cells. J Biol Chem. 1996; 271: 13504-14.
5. Gottlieb E. Cancer: The fat and the furious. Nature. 2009; 461:44-45.
6. Chao C, Haque R, Caan BJ, Poon KY, Tseng HF, Quinn VP. Red wine consumption not associated with reduced risk of colorectal cancer. Nutr Cancer. 2010; 62:849-55.
7. Sharifi N. Antioxidants for Cancer: New Tricks for an Old Dog? The Oncologist.2009; 14:213-215.
8. Millen AE, Dodd KW, Subar AF. Use of vitamin, mineral, nonvitamin, and nonmineral supplements in the United States: the 1987, 1992, and 2000 National Health Interview Survey results. In: J Am Diet Assoc. 2004; 104:942–50.
9. Maxwell SR. Antioxidant vitamin supplements: update of their potential benefits and possible risks. Drug Safety. 1999; 21:253–66.
10. Herbert V, Subak-Sharpe GJ, Hammock D, eds. The Mount Sinai School of Medicine Complete Book of Nutrition. 1990; New York (NY): St Martin's Press.
11. Herbert V. The antioxidant supplement myth. Am J Clin Nutr. 1994; 60:157.
12. Herbert V. The value of antioxidant supplements vs their natural counterparts. J Am Diet Assoc .1997; 97:375–6.
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—About our writer:
Dr. Rumi Ghosh has a Ph.D. in Pharmacy and works as an Assistant Professor of Pharmacology at the University of Mumbai. She has worked on projects for the C.S.I.R, I.C.M.R. and the University of Mumbai. She has experience in medical writing, report writing and article writing for pharmacy and medical journals. She has a number articles published in international journals. She is currently based in Thailand but travels to India quite frequently.
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