Warning on Tomatoes and Prostate Cancer
Photo: C.P. Storm/Creative Commons
Bad news: lycopene, an anti-oxidant found in large quantities in tomatoes, doesn't prevent prostate cancer.
Worse news: Beta-carotene might actually increase the risk of developing an aggressive form of prostate cancer, according to a study published in the journal Cancer Epidemiology Biomarkers & Prevention.
So men can stop stuffing themselves with tomatoes in the hopes of warding off prostate cancer.
Researchers carefully measured the amount of anti-oxidants in 28,000 men's blood, looked to see who among their study subjects developed prostate cancer and compared them to those who had not developed cancer. (This is called a case-controlled study and as such is not definitive but merits further exploration.)
The investigators found no evidence that lycopene offers any protection against developing prostate cancer.
At least, lycopene doesn't increase the risk of developing prostate cancer either.
Alas, the study investigators found that high levels of beta-carotene, a popular vitamin supplement, was linked to more cases of cancer that had spread beyond the prostate.
Whether beta-carotene actually causes the increased risk of aggressive prostate cancer is, of course, an open question that case-controlled studies, like this one, are not designed to answer. But the findings echo another beta-carotene study from 1996 that was randomized, double-blind and placebo-controlled (the most rigorous scientific study design available.) The 1996 study found that smokers who take even modest amounts of beta-carotene have a higher risk of lung cancer. Presumably the vitamin fueled the cancer's growth.
Next question, posed by Tom Paulson at the Seattle Post Intelligencer: Will Heinz stop marketing its Classico pasta sauce as one way to reduce men's risk of prostate cancer? (Kudos to Paulson for bringing up the advertising link, but he may want to brush up on the differences between lycopene and beta-carotene, which he confused in his article.)
Bottom line: Eating lots of vitamins or even lots of tomatoes won't make up for an unhealthy lifestyle. And even if you do everything right, you can still develop cancer. Tomatoes are food and should be enjoyed as food, not taken as medicine.
Sources: U Peters, et al. Serum Lycopene, Other Carotenoids, and Prostate Cancer Risk: a Nested Case-Control Study in the Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial. Cancer Epidemiology Biomarkers & Prevention 16, 962-968, May 1, 2007
GS Omenn, et al. Effects of a Combination of Beta Carotene and Vitamin A on Lung Cancer and Cardiovascular Disease. New England Journal of Medicine; Volume 334:1150-1155, May 2, 1996.
2 comments:
It seems that we (the public) have an insatiable desire to hear news of food substances that help prevent disease. It is always a dangerous thing because such news is almost always retracted after further scientific investigation. I think you hit it on the head. Eating a lot of a certain food item cannot make up for an unhealthy lifestyle.
Other examples of this sort of thing include:
1. In January 2006 the American Heart Association reported that a review of 22 studies on the effects of soy protein with isoflavones demonstrated minimal or no benefit on cholesterol and therefore they could not recommend the use of isoflavone supplements in pills or food for the prevention of heart disease.
2. In February 2007 the Boston Globe reported that the most rigorous study of raw garlic and garlic supplements concluded that garlic 'stinks at' lowering cholesterol.
3. In 2006 FOX News wrote about a 2004 review of 7 clinical trials that attempted to examine whether cranberry juice/products prevented urinary tract infections (UTI’S). The review concluded that there was no evidence that cranberries could prevent UTI’S in men, women and children.
We all (me included) want our shortcuts--don't we? Thanks for the other examples.
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