Is multivitamin use really associated to an increased risk of breast cancer?

I’m bit disappointed with your presentation, and I’m wondering why you exactly choose this multi vitamin study to underpin your conclusion in this video. The Swedish cohort was from 2010 and in April of this year a meta-analysis, which is scientifically stronger in terms of proof, concluded : “Multivitamin use is likely not associated with a significant increased or decreased risk of breast cancer, but these results highlight the need for more case-control studies or randomized controlled clinical trials to further examine this relationship.” […]

Louis / Originally commented on Multivitamin supplements and breast cancer


Thank you so much Louis for taking the time to contribute! It is such a relief to see that meta-analysis come out. This video was queued up from my volume 5 DVD, reviewing the peer-reviewed nutritional science published between Spring 2010 to Spring 2011, and so I just missed it (it wasn’t indexed by the National Library of Medicine until August 19, 2011).

Of course negative findings don’t automatically “cancel” out positive findings. As one of my research preceptors once quipped: “if two people drill for oil in Texas and one finds oil and the other does not, one can’t conclude that the question of whether or not there is oil in Texas remains undetermined.” Similarly, the conclusion from the 2010 study profiled in the video is not necessarily invalidated: “These results suggest that multivitamin use is associated with an increased risk of breast cancer. This observed association is of concern and merits further investigation.” But it’s nice to know that if there is an effect it’s not one that has been replicated!

The critical question remains: should women take multivitamins or not? That depends on the risks versus benefits like any other life decision. Since both the risks and the benefits appear equivocal (see for example the National Institutes of Health State-of-the-Science Conference Statement on multivitamins, PDF here) I agree with the Cleveland Clinic Journal article I featured and would recommend women take the money they would have spent on the pills and instead buy some produce with more proven benefits (see my Breast Cancer and Diet post, for example). A similar recommendation can be made for men (as a similar meta-analysis likewise thankfully casts doubt on the multivitamin link there as well).

Until we know more, I agree with the conclusion from the meta-analysis you cite: “Until further studies assist in clarifying the association between multivitamin use and increased or decreased risk of breast cancer, health-care professionals should open discussions with their patients regarding multivitamin use and risk of breast cancer.”

Addendum: Reported in today’s Archives of Internal Medicine, a study from Iowa Women’s Health Study suggesting that multivitamin use may actually shorten women’s lives. To quote the editor: “Because commonly used vitamin and mineral supplements have no known benefit on mortality rate and have been shown to confer risk….A better investment in health would be eating more fruits and vegetables…”

Image Credit: United States Navy ID 110429-F-NJ219-021 / Wikimedia Commons

  • Harel

    My personal philosophy (developed not in a vacuum but informed by the overall “whole” of medical research I’ve read about in the last quarter century) is pretty strongly in favor of what you suggest Dr. Greger – natural whole foods over human supplements (or drugs, etc) I rarely take anything other than B12 and vit D (doctor prescribed) for this reason, and prepare almost all my vegan meals from scratch. That having been said, there is a huge question that seems to be left unaddressed (from what I can tell of the summaries here of both/all studies) which stands out: mainstream vitamins with their large number of questionable ingredients (fillers, coloring etc etc – I’m referring to all ingredients other than the vitamins themselves; and even the vitamins may be a case of “not all are created equal” in quality) versus vitamin pills that are not just vegan, but also have the least iffy ingredients. I’d like to see a study differentiate, or try to, between those two classes. Then there is the issue of possible harmful effects of megadoses. Combine those and ask this question: “mainstream chemicalized vitamins with megadoses, versus, vitamins with saner doses and with the least iffy ingredients (in fillers, coloring, etc) and the most natural sources of the vitamins/minerals” in a well desgined study, on (yet another factor) people who’ve used it long enough to be more likely a difference, say at least several years. I will not predict the latter will do as well or better than whole foods (my guess is whole foods always win, except, when a medical condition specific to the person is such that focused/higher doses have more benefits than negative side effects) but I wouldn’t be surprised if the latter type of vitamins/ingredients/doses do better than, or not as much harm as, the former type (mainstream/lots of chemical additives/fillers/ingredients, some in megadoses, etc). Have any researcher friends you could suggest this study to? ;-)

  • Sarah

    If multivitamins and supplements aren’t regulated and may not even contain the labeled ingredients, how do we know which D3 and B12 vitamin to get?

  • Michael K. Corrie Sr.

    I stay away from multivitamins but eat healthy, non processed foods, and take my favorite supplements, like AMLA, fenugreek. Please do a video on adaptogens like Aswagandha and maca, also my favorites that I recommend to my Yoga students.
    You are my nutrition guru. Keep it up!

  • Shaylen Snarski

    I rely on food for my nutrients, but I do take an organic whole foods based vegan multivitamin because sometimes it can be difficult to eat the amount and variety everyday to meet all your mineral and vitamin needs… mostly minerals is my concern. So for me my multi is an “insurance policy” that I don’t fall behind. I haven’t read all the articles on the studies above so I’m not sure if it’s mentioned in them, but I wonder what fillers and binders were in the multivitamins and also the sources of the vitamins and minerals would be interesting to know. I would imagine this would have a huge impact on results. It would be interesting to see the results of a study of a group of people on certain types of multivitamins, including the purest: organic, vegan, gluten free, yeast free and so on… Unless of course this has already been looked at, though there aren’t many organic, pure multivitamins on the market that I know of, so I would be surprised if it were.