I had to smile when I saw the headline last week on the National Cancer Institute Website: Multi-institution study finds high consumption of vitamin E may lower liver cancer risk.
I first started taking a vitamin E supplement in the 1970s after reading the book, Vitamin E for Ailing & Healthy Hearts by Wilfred E. Shute, MD. It seemed like a good idea back then, and over the years several observational studies were published that associated lower rates of heart disease with higher vitamin E intake. As described in a National Institutes of Health (NIH) Fact Sheet on dietary supplements, for example, a study of approximately 90,000 nurses published in 1983 found that incidence of heart disease was 30 to 40 percent lower in those with the highest intakes of vitamin E, primarily from supplements.
In recent years the role of vitamin E has been investigated in various types of cancer as well. Findings have been equivocal (as have findings of recent, randomized, controlled cardiovascular studies). The SELECT trial, which began in 2001 to determine whether 7 to 12 years of daily supplementation with vitamin E (400 IU) would reduce the number of new prostate cancers in 35,533 healthy men 50 years of age and older, was discontinued in 2008. Analysis found that vitamin E, alone or combined with selenium, failed to prevent prostate cancer.
Furthermore, results from an additional 1.5 years of follow-up (during which subjects no longer received either supplement) showed that men who had taken vitamin E had a 17 percent increased risk of prostate cancer versus men who took placebo. No differences were found among groups in the incidence of lung or colorectal cancers or all cancers combined. Participants in the SELECT trial are still being monitored.
So what are we to make of the latest findings published in the July 17 Journal of the National Cancer Institute with regard to liver cancer? Findings are based on two population-based cohort studies, jointly conducted by the Shanghai Cancer Institute and Vanderbilt University, evaluating 267 liver cancer patients (118 women and 149 men) at centers in China.
"Overall, the take home message is that high intake of vitamin E either from diet or supplements was related to lower risk of liver cancer in middle-aged or older people," said Xiao Ou Shu, MD, PhD, professor of medicine at the Vanderbilt Epidemiology Center, Nashville, Tenn.
Have I increased my risk of prostate cancer by taking vitamin E all these years or decreased my risk for liver cancer? Have I experienced a cardiovascular benefit, or am I at greater risk for some forms of heart disease, as indicated by findings of some recent cardiovascular studies?
Frankly, I have no idea. I just continue to take 400 IU vitamin E daily and hope it is the right choice. But the example of vitamin E highlights some of the difficulties we all face in seeking to make informed choices about our own health.
What are your thoughts on this subject and on the broader subject of regulation of dietary supplements?