A Answers (2)
Andrea Pennington, MD, Integrative Medicine, answeredThe protective effects of vitamins for fighting cancer appear to depend on a cooperative effort between them and other nutrients found diets rich in fresh fruits and vegetables. Vitamin E may be beneficial for the prevention and treatment of specific cancers, including prostate, oral, stomach, and throat cancers. One study reported that people with the lowest blood levels of vitamin E are at higher risk for all types of cancer than those with the highest levels. Some studies have suggested that certain vitamin D compounds may inhibit prostate cancer cells from proliferating.
Environmental Working Group (EWG) answeredExperiments with vitamin supplementation have illustrated the dangers of excessive vitamin intake and shown that supplements are generally ineffective for preventing deaths or disease due to major chronic diseases. In several clinical trials, participants who took elevated amounts of beta-carotene, vitamin E and vitamin A actually had a higher risk of cancer and higher mortality than a control group.
One study tested the effect of daily doses of beta-carotene (30 mg) and retinyl palmitate (25,000 IU) on cancer incidence in 18,314 participants at high risk of lung cancer because of a history of smoking or asbestos exposure. This multi-center trial began in 1985 and was halted in January 1996, 21 months ahead of schedule. It was stopped because of a clear link between vitamin intake and cancer incidence and mortality. Participants who took the vitamins had a 28% higher lung cancer incidence, 17% more deaths overall and a higher rate of heart disease deaths than those who took a placebo.