Thursday, November 15, 2012
Do vitamins prevent cancer? I doubt it.
Recently the newspapers have been describing the results of a study published in the JAMA (Nov 14, 2012) that shows a reduced cancer rate in men who took multivitamins. This was a carefully designed study of over 14,000 male physicians who were over 50 years old. Half of them were given a multivitamin (Centrum Silver) and half a placebo. After about 11 years, men given the vitamin had fewer cancers. This was a surprise. The effect of vitamins on cancer rates has been studied forever it seems, and the end result of many studies is that vitamins don’t prevent cancer. I once took vitamins. Why not? It can’t hurt and might help. That is probably why most of us take them. Eventually I got tired of taking them and stopped. So should I start taking them again? My thought is no. First of all the difference was small. Men taking the vitamin had eight percent fewer cancers. This was statistically significant. They also had 12 percent fewer deaths from cancer although this was not statistically significant. So chance might have played a role in these results. Even more unconvincing about the value of vitamins was that the total death rate in the two groups was the same. At the end of the day, vitamins didn’t save any lives. There were fewer deaths in the vitamin group, but this was nowhere close to statistical significance. Once again chance alone might have led to these results. I looked at the kinds of cancers that seemed to be fewer in the vitamin group. They were all smoking related cancers. Lung, colorectal, bladder. In both groups smokers were rare – only about 3.5 percent of the total. But past smokers were pretty common – around 40 percent. Unfortunately, the one cancer, I, and most men my age worry about, prostate cancer, wasn’t helped by the vitamins. So what to make of all this? First of all, the results of this study are an outlier. Most studies haven’t shown any benefit for vitamins preventing cancer. Second of all they apply only to men. By the way, studies of vitamins preventing breast cancer have been negative. No help. Finally, the vitamins mainly helped smoking-related cancers. So if you are a smoker or former smoker, maybe they might help. Perhaps that would be the next study. But, of course, better not to have smoked at all. One good point. No harm from the vitamins. So, if you want to take them, go ahead. But don’t count on any benefit.