Taking the vitamins E and C or the nutrient beta-carotene doesn't protect against prostate cancer, says the latest study in the continuing, confusing quest to determine when supplements really help health.
The government research, published Tuesday in the Journal of the National Cancer Institute, is among many large studies examining whether these antioxidants play a role in prostate cancer when taken as pills -- instead of when they're consumed as part of an overall healthy diet.
Previous research has yielded conflicting results, and even this new study of almost 30,000 men doesn't settle the issue. Indeed, while vitamin E showed no effect on men overall, the study leaves open the possibility that it might help smokers.
The men were enrolled in an NCI study whose primary aim is to test the value of screening tests for prostate cancer. They also were surveyed about their diet and what supplements they took -- relying on memory, not nearly as precise as other research now under way that controls supplement doses.
Some 1,338 men were diagnosed with prostate cancer within eight years of entering the study. Supplement users were just as likely to be diagnosed as nonusers.
Smokers were 71 percent less likely to be diagnosed with advanced disease if they had taken high doses of vitamin E for many years. But, perplexingly, the risk of earlier-stage cancer increased among vitamin E-using smokers.
Smoking itself raises the risk of prostate cancer, and even if further research concludes that vitamin E somehow tempers that risk, kicking the habit would be far more protective, Harvard University scientists caution in an accompanying editorial.