Although we see and hear the word ‘antioxidant’ everywhere these days, a survey conducted by Wakefield Research for MonaVie, a nutritional products company, found that 92% of respondents could not successfully define what an antioxidant is and 91% could not recognize at least one food source that is rich in antioxidants. Shockingly, 75% of Americans still say that they try to eat antioxidant-containing foods.
Antioxidants are molecules that neutralize free radicals. Free radicals are molecules that damage living cells. Free radical production occurs naturally, but increases with exposure to pollution, radiation, cigarette smoke, and herbicides.
The National Center for Complementary and Alternative Medicine (NCCAM), a division of the National Institutes of Health, has issued the following statements regarding antioxidants:
- Rigorous scientific studies involving more than 100,000 people combined have tested whether antioxidant supplements can help prevent chronic diseases, such as cardiovascular diseases, cancer, and cataracts. In most instances, antioxidants did not reduce the risks of developing these diseases.
- Concerns have not been raised about the safety of antioxidants in food. However, high-dose supplements of antioxidants may be linked to health risks in some cases. Supplementing with high doses of beta-carotene may increase the risk of lung cancer in smokers. Supplementing with high doses of vitamin E may increase risks of prostate cancer and one type of stroke.
However, the NCCAM points out the many reasons why studies have shown less disease among people who eat the most fruits and vegetables, while other research has found little evidence that antioxidants prevent disease. Individuals who eat the most fruits and vegetables also are probably less likely to smoke, more likely to exercise, etc. Many of the studies look at large supplemental doses of antioxidants, while the effect of consuming smaller quantities in whole foods is perhaps more beneficial. Furthermore, the chemical composition of antioxidants found naturally in foods are different from those used in supplements. Vitamin E found in foods has eight forms, while vitamin E supplements consist of only alpha-tocopherol.
It also is possible that specific antioxidants are more effective for different diseases (eg, lutein might prove more beneficial for the eyes than it is for preventing cancer). It may take decades for the benefits of antioxidants to become evident, and the studies are not long enough to see the results. Antioxidants are perhaps most helpful to those individuals who are under a high degree of oxidative stress, but studies use the general population as subjects.
There are many antioxidants (possibly thousands), but some of the more commonly described include:
- Beta-carotene – found in dark-green leafy vegetables, broccoli, apricots, cantaloupe, carrots, sweet potatoes, pumpkin, and winter squash
- Lutein – found in collard greens, spinach, kale, and many other fruits and vegetables
- Lycopene – found in tomatoes, watermelon, guava, papaya, apricots, pink grapefruit, and blood oranges
- Selenium – found in meat, bread, and Brazil nuts
- Vitamin A – found in fortified milk, cheese, cream, butter, margarine, eggs, and liver
- Vitamin C – found in many fruits and vegetables, including citrus fruits, tomatoes, broccoli, salad greens, strawberries, watermelon, cabbage, and sweet potatoes
- Vitamin E – found in soybean oil, corn oil, cottonseed oil, safflower oil, wheat germ, whole grains, green leafy vegetables, nuts, corn, seeds, olives, egg yolks, and liver
Simply because free radicals contribute to chronic disease, we cannot assume that antioxidants will prevent those same diseases. Until further, longer duration studies are completed, we simply do not know enough to state that antioxidants can help prevent disease. However, we do know that fruits and vegetables are healthful foods for many reasons other than their antioxidant content.
References and recommended readings
Antioxidants: beyond the hype. Harvard School of Public Health Web site. http://www.hsph.harvard.edu/nutritionsource/antioxidants/. Accessed January 24, 2014.
National Cancer Institute, National Institutes of Health. Antioxidants and cancer prevention: fact sheet. Cancer.gov Web site. http://www.cancer.gov/cancertopics/factsheet/prevention/antioxidants. Accessed January 24, 2014.
National Center for Complementary and Alternative Medicine. Antioxidants and health: an introduction. National Institutes of Health Web site. http://nccam.nih.gov/health/antioxidants/introduction.htm. Published May 2010. Updated November 2013. Accessed January 24, 2014.
Contributed by Elaine Koontz, RD, LD/N
Review Date 1/14