Do multivitamins cause breast cancer? An observational cohort study conducted in Sweden, recently published in the American Journal of Clinical Nutrition, suggests they may.
In such trials, people answer questions about their lives, and are then observed to see what happens to whom. These studies can be powerful when large -- this one followed nearly 35,000 women for close to ten years -- but they are never as definitive as intervention trials in which people are randomly assigned to treatment A or treatment B. People who decide to do 'A' may differ in a whole variety of ways from people who decide to do 'B.'
In this case, they did. Women who took multivitamins also used oral contraceptives and hormone replacement therapy more, and exercised less, for example, than the women who did not take the supplements.
Roughly 25 percent of the women in the study routinely took a multivitamin, and were 19 percent more likely to be diagnosed with breast cancer after adjusting for other potential explanations.
There's the headline, but let's work those numbers over just a bit. That 19 percent risk increase, if real, is a "relative" risk increase. How big is the absolute risk?
A total of 681 cancers developed over roughly 10 years in 26,312 women not routinely taking multivitamins. The risk of breast cancer in these women in any given year was thus about 0.26 percent.
In the 9,017 women taking multis routinely, there were 293 breast cancers over that same decade. Among these women, then, the absolute risk of breast cancer in any given year was 0.32 percent.
The relative difference between a risk of 0.32 percent and 0.26 percent is, indeed, about 19 percent. But the absolute difference is 0.06 percent. In other words, if multivitamins are truly the cause of the apparent risk difference, they would increase your breast cancer risk by considerably less than one tenth of one percent; 1,667 women would need to take multivitamins for a year before one extra case of breast cancer occurred.
So, clearly, there is no cause for panic.
But there is cause for reflection, and perhaps reorientation. After all, we take multivitamins in the hope they will do us good, not in the hope they won't do us harm. And while evidence is scant that they do us good, this study is not the first to hint of potential harm -- other researchers have found a similar association between multis and breast cancer.
There are plausible mechanisms. Tumors grow less well when certain nutrients -- folate prominent among them -- are in rate-limiting supply. A multivitamin might "feed" cells in a tumor.
If folate is the relevant nutrient in Sweden, it may not be relevant in the U.S., since we fortify our food supply with folate (doing so dramatically reduces the occurrence of a congenital anomaly called 'neaural tube defect') and the Swedes do not. Even Americans NOT taking multivitamins are getting supplemental folate. Folate, however, is just one potential explanation for the findings.
Of course, if what prevents a tumor from growing is having too little of a nutrient to feed the tumor cells, it raises a question: is there enough of the nutrient to feed healthy cells optimally? Not getting cancer is important, but so is being vital and energetic. This study could not address that issue.
If we want optimal nutrients for healthy cells but don't want to feed tumors, the source of nutrients may be crucial. The best source -- the source strongly and consistently associated with lower risk of just about every disease -- is wholesome foods. No supplement is a substitute for them.
But something called a "whole food based" supplement may come close. Products such as Juice Plus, currently under study in my lab, take all of the nutrients from plant foods and concentrate them into capsules for those who simply can't or won't eat the recommended servings of fruits and vegetables daily (that's most Americans!). Unlike multivitamins which take nutrients out of context and repackage them, whole food supplements maintain the natural array and concentration of nutrients -- thousands of them -- found in the foods themselves. It may be that nutrients only work as they should in concert, like the various instruments in a symphony orchestra. There is both science and theory to support this notion, although no decisive evidence yet that whole food supplements promote health over the long-term while avoiding potential harms of standard multivitamins. But it seems plausible to me that this might be true, and further study is well justified.
Finally, not all nutrients are equal when it comes to breast cancer risk. Supplementation with calcium, and possibly vitamin D, in the Swedish study were actually associated with reduced risk. So along with "don't panic," let's add: don't toss out the baby with the bathwater. I favor vitamin D supplementation, vary my calcium recommendations depending on diet, and routinely encourage supplementation with omega-3 oils. I have not yet abandoned use of multivitamins, but am growing steadily less enthusiastic.
If multivitamins increase breast cancer risk, the increase is very, very small. While quite meaningful at the population level, it is very unlikely to make a difference in your life. Still, the association could be real -- and there are other ways to optimize your nutrient intake. The best of these is to eat those fruits and vegetables Mom recommended all along.
Dr. David L. Katz; www.davidkatzmd.com
Follow David Katz, M.D. on Twitter: www.twitter.com/DrDavidKatz
Mark Hyman, MD: Vitamin D: Why You Are Probably NOT Getting Enough and How That Makes You Sick
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Breast cancer - Wikipedia, the free encyclopedia
National Breast Cancer Foundation® Official Site - Information ...
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Breast cancer - Wikipedia, the free encyclopedia
WebMD Breast Cancer Center: Types, Symptoms, Causes, Genes ...
National Breast Cancer Foundation® Official Site - Information ...
NO, it doesn't .
It suggests that healthy tissue grows better and faster, including cancer tissue.
The header of this is Big Pharma hysteria.
I started taking supplements two weeks ago, and I think it's the Vitamin C which is causing me problems.
Now I'm more inclined to commit to healthy eating and regular juicing of fresh vegetables as a way to get a large and trusty does of many vitamins.
Daily intake of a variety of fresh and locally grown whole food seems the safest way to go.
This is something the research community is very poor at communicating to the general public (perhaps because it is a caveat to any conclusion they draw); and the point should be made early and often with every 'finding' that is published...
There is an integrity of the body that evolved over time that perhaps cannot process large amounts of unnatural sources of food and medicine and over time they build up and cause cancer.
I was taught in herbology 101..that the human body can assimilate natural sources of vitamins much better than anything bought in a bottle.
There seems to be some sort of mythical awe concerning vitamins in the U.S.. If products containing GMOs or hormone milk had shown even a slight increase in cancer incidences, the outcry would have been tremendous.
However, a great deal of research has shown that natural environs of many vitamins assist in the uptake of these vitamins in the human body; probably because our bodies have evolved over millenia to digest them in these contexts... (For example, the oils in hot peppers assist in the uptake of the highly concentrated vitamin-C they contain; various molecules common in spinach and other leafy greens assist in the uptake of the B-vitamins they contain; etc.).
March 30, 2010
Dispatch: Multivitamins and Breast Cancer
By Curtis Porter
A Reuters headline asks “Could multivitamins raise breast cancer risk?” based on a decade-long study published in the American Journal of Clinical Nutrition which followed 35,000 Swedish women and their self-reported supplement use.
“This is a horrible headline, and a typical example of what epidemiologists are forced to resort to in order to get attention for their work, especially when it is an observational study of nutrition,” says Dr. Ross. “Many people like to take multivitamins because they imagine that there’s some magical health benefit, but with a few exceptions, almost every study I’ve seen about these supplements has failed to show that they have any beneficial effect, and some have proven harmful.
“When you consider that this study is based on people reporting their own use of vitamins over a decade, and that the increase in breast cancer risk that they found was only 19%, I have to ask you: does this study warrant this headline? It’s only slightly above the level of junk science because of its size, but to extrapolate a 19% increase in risk based on self-reporting is absurd.”
On a more personal note, I completely eliminated HOT FLASHES by removing dairy, ALL dairy from my diet. No cheese puffs, no ranch dressing, no milk or yogurt for two weeks. Then incrementally added dairy sparingly to find the offending product. I will not itemize my whole experience, but every woman I recommend this to have the same results. Hot flashes disappear.
We absorb hormones quickly and eliminate them slowly, therefore accumulate excess amounts over time. It would sometimes require a whole week for the hot flashes to subside after eating a meal laced with offending dairy. Cheeses like feta, colby, and cheddar were the most reactive.
Subsequently dairy is very very limited in my diet, and only organic at that.
If one in every eight women get breast cancer in their lifetime, then its root must be in something very common.
There is ample material to discuss without resorting to insults. Can't we raise the bar?
While it is true that most doctors are not formally trained in nutrition, I am. After an Internal Medicine residency, I did a second residency in Preventive Medicine, with a focus on nutrition in the prevention of chronic disease. I have written two editions of a nutrition textbook, directed nutrition courses at Yale for both medical and nursing students for years, and routinely participate in the training of nutrition professionals- such as dietitians. And so on; more details are available on my website for those interested.
I am not on the payroll of any drug company.
I am not on the payroll of Juice Plus, or any supplement company.
My opinions are just that- my opinions, not prostitution.
That doesn't mean you shouldn't disagree with me- some of you, doubtless, will. But I promise I will never waste your time, nor mine, writing in an area where I don't have genuine expertise, nor will I ever function as a mouthpiece for any views other my own. My opinions are not for sale.
My hope is for comments that offer perspective about content, rather than presumption about character. Reasonable people can disagree- that disagreement is most constructive when predicated on reason. Uninformed presumption and unsubstantiated accusations sully debate- and divert argument from the channels in which it may best cultivate perspective and insight.
Thanks for considering-
DK
Please accept that the following questions are not meant to be insulting, and please excuse my ignorance because I am neither a doctor nor a nutritionist.
1. Is it not true that the AMA recently advocated supplementation with multi vitamins, but that its recommendation is so basic and nonspecific that it could be construed to include formulations which might be classed as "supermarket brands" ?
2. Do you consider all multi vitamins to be equal, or do you concede that some formulations are more aligned with the findings of current research?
3. Do you believe that the quality of ingredients in all multi vitamins is equal, or do you concede that some manufacturers employ better ingredients and/or better manufacturing processes than others?
4. Do you believe or suspect that the formulation and/or the quality of ingredients of a multi vitamin might contribute to its efficacy and/or its possible harmful effects?
5. Can "whole food based" supplements also vary in formulation, quality of ingredients, and/or manufacturing process?
6. Do you believe that people can effect the state of their own well being by becoming increasingly educated about, and by self administering supplements; or is this a futile endeavor due to the current often conflicting state of research and development?
Please accept that these are sincere and not rhetorical questions as I am trying to do the best I can with my own maladies.
We get a lot of suggestions to pass on to women regarding what has worked, or specific products and supplements. There is not a one size fits all, and there are many variables that affect the efficacy, uptake, compliance, etc.
I also look at relative versus absolute. There is a tendency to looik at the problem in an absolute way, and the proposed solution in a relative way. Skews the data, like the study discussed.