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Cancer Myths (5 posts)  RSS

The Bottom Line on Soy and Breast Cancer Risk

August 02, 2012

By Marji McCullough, ScD, RD

 

EDITOR'S NOTE: Dr. McCullough added the following statement 4/8/14 in response to questions related to sources of isoflavones:

Research on soy and cancer is highly complex, controversial, and evolving.

When concerns about soy are raised, they generally focus on findings from rodent models of cancer which tend to use isolated soy compounds like soy protein isolate or high doses of isoflavones (compounds found in soy).  However, soy is metabolized differently in humans than it is in mice and rats, so findings in rodents may not apply to people. (See: http://www.ncbi.nlm.nih.gov/pubmed/16614407 for more on this.)(Setchell, AJCN, 2011).  There is no evidence in the medical literature that soy protein isolate is bad for humans, compared to other forms of soy. Soy protein isolate is often used as a supplement in randomized studies of the effects of soy on health and none of these studies have shown harm.

Most of the studies suggesting benefits of soy consumption in people have measured how much soy foods people are eating, including tofu, soybeans, and soy milk.  These foods are more commonly eaten in Asian countries. In the U.S., purified forms of soy are used in the food supply, including in energy bars and soy hot dogs.  The few US studies that have measured these forms of soy do not suggest harm.    

More research is needed to understand the relationship between specific forms of soy and doses of isoflavones on cancer risk and recurrence. We also need to learn more about childhood exposure to isoflavones and risk of cancer. Until more is known, if you enjoy eating soy foods, the evidence indicates that this is safe, and may be beneficial (but note that miso, a fermented soy product, is high in sodium.)  It is prudent to avoid high doses of isolated soy compounds found specifically in supplements, as less is known about their health effects. As for other "hidden" sources of soy proteins, the evidence to date does not suggest harm or benefit. However, if you are concerned about these products, you can choose to avoid them.  


 

Before writing a blog about soy and breast cancer, I took an informal poll of a few friends to get a sense of what women believe about soy.  I asked them, "What do you know about eating soy food?  Is it good for you? Not good for you?" (I didn't even mention breast cancer.)  The responses I got were,  "I think it acts like estrogen in the body"; "Consuming any soy products increases the risk of breast cancer"; "I don't eat it a lot because I heard something negative but I can't remember what it was;" and "I've heard you should only have it in moderation."  Apparently, people are hearing that soy may not be good. But what's the truth? In this blog I'll walk you through what we know and what we don't know about soy and breast cancer, and give you some practical tips on eating soy. More...

Breast Cancer Myths: Separating Fact from Fiction

October 24, 2011

By Ted Gansler, MD, MBA, MPH



You have probably seen and heard a lot about breast cancer during the past few weeks, but as we approach the end of this year's breast cancer awareness month this is a good time to ask how much of the information you encountered is actually true. See if you know which of the following statements are true and which are false... More...

Will a vitamin a day keep cancer away?

August 16, 2011

By Marji McCullough, ScD, RD

 

Editor's note: Dr. McCullough added the following statement 12/20/13 in response to new studies being released:

Recent findings on multivitamin supplements published after the posting of this blog deserve mention. In 2012, the results of a randomized controlled trial (RCT) of a daily multivitamin supplement were published, showing a small but statistically significant lower risk of all cancers combined in male physicians followed over 11 years.  The supplement included 30 nutrients at levels similar to that found in a regular diet in the United States (≤100% recommended daily allowance (RDA)).  The U.S. Preventive Services Task Force (USPSTF) recently updated their review of vitamin and mineral supplements for the primary prevention of cancer and cardiovascular disease (CVD) and found there isn't much evidence that multivitamins or supplements help prevent cancer or CVD. But they add that a small benefit from multivitamin supplements on cancer in men was found, based on this study and an earlier RCT in France. The study in France found lower rates of cancer in men, but not women. The authors speculate that this may have been due to worse nutritional status - a generally less nutritious diet in the men - but more research is needed. In the study with the male physicians mentioned above, they all were well nourished but still saw some benefit.

There are still questions to answer about multivitamins and cancer from the RCTs: why only in men? Does whether you have a nutritious diet matter, and to what degree? Are these findings able to be replicated? Longer follow-up from these trials (to see long term effects) may provide more clues. In the meantime, these studies show that lower-dose multivitamins (with ≤100% RDA) appear safe and don't raise risk of cancer or CVD. Still, the best way to get nutrients is through a healthy diet, and the cost of multivitamins can add up. People should discuss the pros and cons of supplement use with their health care professional.

 

Original blog, 8/16/2011


Can popping vitamin pills prevent cancer? The simple answer is no, based on what we know so far. In fact, some vitamin supplements have even shown harm. What I'm talking about mostly are pills containing individual nutrients in amounts that are greater than that found in food. Before you stop reading, thinking this is simply another "just eat your vegetables" message, let me give you a little history.


Toward the end of the last century, scientists observed that people with healthy diets, and with higher levels of certain phytochemicals ("phyto" for plant) in their bloodstream, such as beta-carotene, had lower rates of cancer. But observations don't prove cause and effect.


So, after careful evaluation of promising dietary compounds, the scientists began planning randomized, placebo controlled clinical trials ("RCTs") with tens of thousands of healthy people to see if taking supplements of individual phytochemicals could actually prevent cancer. RCTs are considered by most to be the gold standard for proving something works. Most of the supplements tested were antioxidants, which are chemical compounds that combat "free radicals" in the body that can damage DNA and possibly lead to cancer. More...

Is your car killing you with benzene?

July 19, 2011

By Ted Gansler, MD, MBA


An e-mail message that may have come into your inbox recently claims that dangerous levels of a cancer-causing chemical (benzene) are released from the plastic surfaces of automobile interiors. The e-mail recommends opening the vehicle's windows to remove the benzene before using the air conditioner.

 

Although benzene is linked to leukemia, very little research has looked at whether the interior surfaces of cars release dangerous amounts of benzene, and the information that is available does not support the e-mail's claims. More...

Filed Under:

Cancer Myths | General | Ted Gansler

Busting Clinical Trials Myths

April 26, 2011

By Katherine Sharpe, MTS


"It might be time to consider a clinical trial." I have heard this many times in my work with the American Cancer Society. Unfortunately, in most cases, people think of clinical trials as the option of last resort, so they consider one only when all other treatment options have failed.

 

But the truth is that clinical trials should always be considered as a treatment option. In fact, there are clinical trials for almost every type of cancer and stage of disease - there are even clinical trials for cancer prevention! Without clinical trials, we would see virtually no advances in cancer treatment. 

 

The good news is that more and more people are considering a cancer clinical trial when they are first diagnosed - and that helps speed up breakthroughs in cancer care. But there is clearly a need for more people to learn about and consider this option.

More...

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