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.

4 comments:

Greg Pawelski said...

I find your comment about prostate cancer not being helped by vitamins, interesting. The Harvard Men's Health Watch had the adage that even if multivitamins don't help, they won't hurt. However, they had a reappraisal of that advice. They noted that some studies had linked multivitamin use to prostate cancer. More convincingly, studies had linked "high intakes" of folic acid to colon polyps, the precursors of colorectal cancer. Researchers speculate that high intakes of folic acid, which was first added to grain products in the 1990s, may have contributed to an increase in colorectal cancers in the mid-1990s.

But what does all of this have to do with multivitamins? Now that folic acid is added to so many grain products, it's easy to see how a healthy diet, combined with a multivitamin, could boost a person's daily intake to 1,000 mcg or more, potentially increasing the risk of colorectal and possibly prostate and breast cancers. In light of this research, Harvard Men's Health Watch suggests that the average man give up the multivitamin, at least until scientists solve the puzzle of folic acid and cancer. I'll continue taking my Centrum Silver, until I'm dead.

Anonymous said...

I'm sorry if this is not the proper medium of posing such a question and I apologize for English is not my first language. My mother has stage 4 colorectal cancer and it seems the treatment, at least for now, is chemo for as long as possible. How long can a patient remain on chemo is my question. If she tolerates it well could she stain on for a few years? She will be staring next week on a FOLFIRI regimen, day 1 in the hospital and 2 at hom then repeat every two weeks. Merci de Montreal.

Herman Kattlove said...

With stage 4 cancer, chemotherapy is usually continued as long as the cancer is still being held in check. Sometimes after several treatments, side effects become too much of a problem and different drugs are then used.

kurt black said...

I think that prevention and living well at a young age is very important. My kids take vitamun everyday and I am strict about it. The key to health is to be aware.