Last week, on one of the MM listservs, a rather heated discussion started from a study on prostate cancer and multivitamins recently published by the National Cancer Institute. Prostate cancer patients who take multivitamins, a list member wrote, are more likely to have more virulent cancers than those who do not. WHAT??? I couldn’t believe my eyes, so I did a bit of sleuthing. I discovered that Internet was plastered with scary news headlines, such as Multivitamins linked to prostate cancer, Multivitamin prostate warning, and even Vitamins may hike deadly prostate cancer risk, and Vitamins Tied to Prostate Cancer. Multivitamins had suddenly become Vitamins. Helloooo??? I immediately looked up the full study: http://tinyurl.com/2zmbxd.
According to the study, a very high intake of multivitamins increased the risk of a more rapid progression of this cancer in the advanced or fatal stages, BUT that same intake was not found to be harmful in the early stages or indeed in the prevention of prostate cancer. Therefore, multivitamins do NOT cause prostate cancer. A key point. One of many. Keep in mind that very high intake apparently meant taking MORE than seven multivitamins a week. Now, that is A LOT of vitamins. A few questions that popped into my mind were: what did these patients eat? Why were they supplementing with so many multivitamins? What about other factors? The study provides rather wishy-washy information on diet, limited to red meat, fish, alcohol and tomatoes. There are so many things involved in cancer that I am amazed that anybody reading this study and, indeed, the researchers themselves, could have come to any conclusions whatsoever.
The researchers report that, while heavy multivitamin users who also took an extra selenium, folate or vitamin E supplement had a statistically significant increased risk of localized prostate cancer, there was no such increased risk for those who took selenium, folate or vitamin E as individual supplements. This small but interesting fact is rather buried in the study, but I think it is worth mentioning. Multivitamins no, individual supplements yes.
Even more importantly, Heavy multivitamin use versus never use was associated with an increased risk of both advanced prostate cancer [ ] and fatal prostate cancer [ ] among men with a positive family history of prostate cancer, whereas no association was apparent among those without a family history. A few paragraphs later: confounding associations between individual agents [read: vitamins] that we were unable to assess and the risk of prostate cancer among men with a positive family history in our study were possible. Confounding is right.
Another tasty morsel: In our study, prostate cancer PSA screening was most frequent among heavy users of multivitamins, consistent with survey data [ ] showing men who used supplements were more likely to have PSA examinations than nonusers. Thus, it is possible that the positive association with heavy use of multivitamins along with certain supplements was spurious because more intensive screening led to increased diagnosis of localized prostate cancer in groups that used the supplements. Hmmm.so, unless my English fails me (which would not surprise me, since I have lived in Italy more than half my life ), vitamin-takers are more likely to get screened for prostate cancer. I think the implications are obvious. Spurious, indeed!
But the best is yet to come: excessive intake of certain individual micronutrients that are used in combination with multivitamins may be the underlying factor that is related to risk and not the multivitamins themselves. What, what, WHAT?! So multivitamins MAY not be the culprits, after all? Then what is the point of this study? What were those news headlines shouting about?
The abstract concludes: These results suggest that regular multivitamin use is not associated with the risk of early or localized prostate cancer. The possibility that men taking high levels of multivitamins along with other supplements have increased risk of advanced and fatal prostate cancers is of concern and merits further evaluation. Suggest, possibility ? Hardly a firm denunciation of multivitamins.
My wrap-up: the multivitamin/prostate cancer study is inconclusive, and the hype surrounding it is dangerous. I would not be surprised to learn that many cancer patients are now too afraid to take any vitamins at all. However, if I took vitamins (I do not, actually, not on a regular basis), this study would not convince me to stop taking them. Not in the least. Oh, and did I mention that the assessment of multivitamin use was based on a “self-administered, mailed food-frequency baseline questionnaire”? No comment. My advice: when you read a catchy headline similar to the above-mentioned ones, disregard it and go read the source for yourself.
Good sleuthing Margaret,
I notice the figure of seven multivitamins per week, and that’s exactly what I take myself. One a day. It doesn’t seem excessive; I hope it isn’t!
You analysis is precious!! You point out, you question every point: What a gift to anyone who reads it!
Medical reporting is incredibly flaky.. and you prove it, piece by piece. I thoroughly enjoyed reading this chapter of yours.
Bless you for a great piece of investigation and writing. Thank you.
Inexorable logic, Margaret, cold and ruthless. A clinical
dissection worthy of a surgeon.
7 multivitamins a week is undoubtedly the dosage taken by most people who take multivitamins. I don’t, so have no idea if there are warnings on the labels not to exceed 1 a day. But people who take them do so because of the convenience of taking 1 pill rather than the 2 or 3 fistfuls of pills and capsules I take every day.
Good piece of debunking, Margaret
It doesn’t appear from your study of the study that any logical conclusion can be reached, which simply shows that half of what you read in the papers is not true, and the other half is simply false. Nice piece of debunking, Margaret.
You have shown us that when someone’s conclusions have a certain smell of disbelief about them, it is best to check them out.