Highlights
Antioxidants
- Antioxidant vitamins such as vitamins A, C, E, and beta carotene are clearly important to good health and should be obtained from a healthy diet.
- While moderate supplement doses may be reasonable, high doses of antioxidant supplements may be dangerous. Because they protect cancer cells in the same way they protect healthy cells, antioxidants may increase the risk of recurrences in people who have cancer, and beta carotene supplements increase smokers' risk of lung cancer.
- Studies have found that vitamin E and beta carotene supplements reduce the adverse side effects associated with radiation therapy – but they also reduce the effect of radiation, possibly, and cause an increased risk of recurrences.
Supplements & Cancer
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Overall, most individual supplements have not been proven to protect against cancer. A few exceptions include the following:
- A major study found that men who took selenium for six or seven years reduced their risk of prostate cancer by 52%.
- A 2005 study found that in one out of four men (those with genetic variations which cause them to be more sensitive to oxidative stress), supplementation with selenium, vitamin E, and lycopene significantly reduced the risk of prostate cancer.
Vitamin E
Although vitamin E has been studied more thoroughly than most vitamins, researchers are still working to determine whether it has particular health benefits, what doses are best, and if high doses are dangerous.
- In a major 2005 study, there was no significant difference in cancer rates between people who took 400 IU of vitamin E daily and those who did not over the long term.
- Those who took the supplement had a slightly higher risk of heart failure than those who did not.
- Additional studies have also linked high levels of vitamin E with an increased risk of heart failure and death.
- On the other hand, other studies show that vitamin E may reduce heart problems in high-risk patients such as certain diabetics.
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