Does Soy Increase Breast Cancer Risk?

Written by Dr. Steve Chaney on . Posted in Soy and Breast Cancer

What Does the Latest Study Say?

Author: Dr. Stephen Chaney

does soy increase breast cancer riskDoes soy increase breast cancer risk?

“To soy or not to soy. That is the question.” If you are a woman, particularly a woman with breast cancer, it is an important question. Some experts say soy should be avoided at all costs. They say that soy will increase your risk of breast cancer. Other experts say soy is perfectly safe and may even reduce your risk of breast cancer.

If you are a breast cancer survivor, the question of whether soy increases or decreases your risk of disease recurrence is even more crucial. You have already endured surgery, chemotherapy, and/or radiation. You never want to go through that again.

 

Why Is There So Much Confusion About Soy?

soy confusionSoy isoflavones decrease estrogen production, strengthen the immune system, inhibit cell proliferation, and reduce the production of reactive oxygen species. These are all effects that might reduce breast cancer risk.

On the other hand, soy isoflavones also bind to estrogen receptors and exhibit weak estrogenic activity. This effect has the potential to increase breast cancer risk.

Cell culture and animal studies have only confused the issue. Soy isoflavones stimulate the growth of breast cancer cells in a petri dish. Soy isoflavones also stimulate breast cancer growth in a special strain of mice lacking an immune system. However, in studies in both mice and rats with a functioning immune system, soy isoflavones decreased breast cancer risk.

The confusion has been amplified by claims and counter-claims on the internet. There are bloggers who are more interested in the spectacular than they are in accuracy (Today we call this fake news). They have taken the very weak evidence that soy isoflavones could possibly increase breast cancer risk and have blown it all out of proportion.

Their blogs claimed that soy definitely increased breast cancer risk and should be avoided at all cost. Their claims were picked up by other web sites. Eventually, the claims were repeated so many times that people started to believe them. A “myth”was created.  I call it a myth, because it was never based on convincing scientific evidence.

In the meantime, scientists looked at the cell culture and animal studies and took a more responsible approach. They said “If this is true, it is an important public health issue. We need to do clinical trials in humans to test this hypothesis.”

It is easy to see why the general public still asks “Does soy increase breast cancer risk?”

 

breast cancer soyWhat Have Previous Clinical Studies Shown?

The question “Does soy increased breast cancer risk” was settled a long time ago. Some studies have shown no effect of soy consumption on breast cancer risk. Others have reported that soy consumption decreased breast cancer risk. A meta-analysis of 18 previous clinical studies found that soy slightly decreased the risk of developing breast cancer (J Natl Cancer Inst, 98: 459-471, 2006 Meta-Analysis-of-Soy-Intake-and-Breast-Cancer-Risk). None of those studies found any evidence that soy increased the risk of breast cancer.

What about recurrence of breast cancer in women who are breast cancer survivors? Between 2006 and 2013 there have been five major clinical studies (soy-and-breast-cancer-recurrence) looking at the effects of soy consumption on breast cancer recurrence in both Chinese and American populations. Once again, the studies have shown either no effect of soy on breast cancer recurrence or a protective effect. None of them have shown any detrimental effects of soy consumption for breast cancer survivors.

A meta-analysis of all 5 studies was published in 2013 (Chi et al, Asian Pac J Cancer Prev., 14: 2407-2412, 2013). This study combined the data from 11,206 breast cancer survivors in the US and China. Those with the highest soy consumption had a 23% decrease in recurrence and a 15% decrease in mortality from breast cancer.

 

breast cancer soy studyWhat Did The Latest Study Show?

In previous clinical studies the protective effect of soy has been greater in Asian populations than in North American populations. This could have been because Asians consume more soy. However, it could be due to other population differences as well. To better evaluate the effect of soy consumption on breast cancer survivors in the North America, this group of investigators correlated soy consumption with all-cause mortality in breast cancer survivors in the US and Canada (Zhang et al, Cancer, DOI: 10.1002/cncr.30615, March 2017).

The data was collected from The Breast Cancer Family Registry, an international research infrastructure established in 1995. The women enrolled in this registry either had been recently diagnosed with breast cancer or had a family history of breast cancer.

This study included 6235 breast cancer survivors from the registry who lived in the San Francisco Bay area and the province of Ontario in Canada. The women represented an ethnically diverse population and had a median age of 51.8 at enrollment.  Soy consumption was assessed either at the time of enrollment or immediately following breast cancer diagnosis. The women were followed for 9.4 years, during which time 1224 of them died.

The results were as follows:

  • There was a 21% decrease in all-cause mortality for women who had the highest soy consumption compared to those with the lowest soy consumption.
  • The protective effect of soy was strongest for those women who had receptor negative breast cancer. This is significant because receptor-negative breast cancer is associated with poorer survival rates than hormone receptor-positive cases.
  • The protective effect was also greatest (35% reduction in all-cause mortality) for women with the highest soy consumption following breast cancer diagnosis. This suggests that soy may play an important role in breast cancer survival.
  • The authors concluded “In this large, ethnically diverse cohort of women with breast cancer, higher dietary intake of [soy] was associated with reduced total mortality.”

In an accompanying editorial, Omer Kucuk, MD, of the Winship Cancer Institute of Emory University, noted that the United States is the number 1 soy producer in the world and is in a great position to initiate changes in health policy by encouraging soy intake.  He said “We now have evidence that soy foods not only prevent breast cancer but also benefit women who have breast cancer. Therefore, we can recommend women to consume soy foods because of soy’s many health benefits.”  In light of this study, has the question “Does soy increase breast cancer risk” been answered?

 

Does Soy Increase Breast Cancer Risk?

soy breast cancer mythEvery clinical study has its limitations. If there were only one or two studies, the question of whether soy increases breast cancer risk might still be in doubt. However, multiple clinical studies have come to the same conclusion. Either soy has no effect on breast cancer risk and breast cancer recurrence, or it has a protective effect.

Not a single clinical study has found any evidence that soy increases breast cancer risk. It is clear that consumption of soy foods is safe, and may be beneficial for women with breast cancer. The myth that soy increases breast cancer risk needs to be put to rest.

On the other hand, we should not think of soy as a miracle food. Breast cancer risk is also decreased by a diet that:

  • Contains lots of fruits and vegetables.
  • Is low in processed grains & sweets and high in whole grains.
  • Is low in saturated & trans fats and high in omega-3 and monounsaturated fats.
  • Is low in red & processed meats and high in beans, fish & chicken.

Furthermore, diet is just one component of a holistic approach for reducing the risk of breast cancer. In addition to a healthy diet, the American Cancer Society recommends that you:

  • Control your weight
  • Be physically active
  • Limit alcohol
  • Don’t smoke
  • Limit hormone replacement therapy unless absolutely necessary.
  • Reduce stress

Does soy increase breast cancer risk?  No.

The Bottom Line

 

  • It is time to put the myth that soy increases breast cancer risk to rest. This myth is based on cell culture and animal studies, and those studies were inconclusive.
  • Multiple clinical studies have shown that soy either has no effect on breast cancer risk, or that it reduces the risk.
  • Multiple clinical studies have also shown that soy either has no effect on breast cancer recurrence in women who are breast cancer survivors, or that it reduces recurrence.
  • The latest clinical study is fully consistent with previous studies. It reports:
    • There was a 21% decrease in all-cause mortality for women who had the highest soy consumption compared to those with the lowest soy consumption.
    • The protective effect of soy was strongest for those women who had receptor negative breast cancer. This is significant because receptor-negative breast cancer is associated with poorer survival rates than hormone receptor-positive cases.
    • The protective effect was also greatest (35% reduction in all-cause mortality) for women with the highest soy consumption following breast cancer diagnosis. This suggests that soy may play an important role in breast cancer survival.
  • No clinical studies have provided any evidence to support the claim that soy increases either breast cancer risk or breast cancer recurrence.
  • On the other hand, we should not think of soy as a miracle food. Breast cancer risk is also decreased by a diet that:
    • Contains lots of fruits and vegetables.
    • Is low in processed grains & sweets and high in whole grains.
    • Is low in saturated & trans fats and high in omega-3 and monounsaturated fats.
    • Is low in red & processed meats and high in beans, fish & chicken
  • Furthermore, diet is just one component of a holistic approach for reducing the risk of breast cancer. In addition to a healthy diet, the American Cancer Society recommends that you:
    • Control your weight
    • Be physically active
    • Limit alcohol
    • Don’t smoke
    • Limit hormone replacement therapy unless absolutely necessary.
    • Reduce stress

 

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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Latest Article

Stress and Jaw Pain

Posted September 19, 2017 by Dr. Steve Chaney

Get Rid Of Jaw Pain Forever

Author: Julie Donnelly, LMT – The Pain Relief Expert

Editor: Dr. Steve Chaney

 

In this article we will show a connection between stress and jaw pain. 

stress and jaw painStress is a part of everyone’s life, but the way you handle it makes a huge difference.  People think of stress coming from challenges like divorce, bills, etc., but it can also come from happy situations. Positive life changes such as getting married or having a baby can also cause stress.

For some people, the solution to stress is to take a yoga class or practice tai chi regularly.  For others, running, exercising, or listening to music eases their mind.

In my Muscular Therapy office, people frequently tell me “I hold my stress in my shoulders,” or “…in my back.” However, a common stress reaction is to clench your teeth tightly. Actually, people hold stress all over their body, from headaches and clenched jaws to foot pain. I want to discuss how clenching your jaws is a common cause of TMJ. Fortunately, it’s a condition that is easy to treat by yourself.

Stress And Jaw Pain

jaw painJaw pain is commonly caused by a shortening of the masseter muscle. The masseter muscle (circled on graphic) is the muscle that contracts to enable you to chew your food.  Normally, as you chew the muscle shortens and then lengthens as you put more food into your mouth.  How can stress and jaw pain be related?  If you are under stress and your teeth are clenched, you miss the lengthening movement. This imbalance causes the muscle to shorten.

Put your fingers on your cheeks so you are pressing into your back teeth.  Now, clench your teeth and you’ll feel the muscle bulge.  If you clench your teeth when you sleep or you tend to clench your teeth when you are upset, you are setting yourself up for TMJ.

Stress And Jaw Pain (TMJ)

TMJ (Temporomandibular Joint) pain is a condition where your jaw bone rubs or “clicks” over the bone that is just in front of your ear. It is painful, and over time it will damage the bones. When you are under stress and clenching your teeth, you are shortening your masseter muscle. A phenomenon called “muscle memory” will cause the muscle to actually get stuck in the shortened position. The now-shorter muscle prevents you from opening your jaw completely.  For example, when you yawn.  As you are trying to yawn, your jaw flips over the bone and it hurts.

Several years ago, I had a client who had such tight masseter muscles that a dental surgeon was going to sever them so she could open her mouth.  This is a terrible solution because it would mean her mouth would hang open for the rest of her life. Fortunately for this client, she had to get medical approval before she could have the surgery.  When Dr. Cohen (the doctor I worked with) felt her masseter muscles, he refused to sign the permission form. He told her that she had to see me first.  Fortunately, I was there at the time.  It took just 30 minutes for me to release the spasms and teach her how to do the treatment.  At the end of the session she was pressing into both masseter muscles and opening her mouth.  She did it easily and without pain!  She started to cry because she came within one day of having this unnecessary surgery.

Her life was changed by just a simple self-treatment!

Self-Treatment For TMJ Pain

stress and jaw pain reliefHere is how to administer TMJ pain relief to yourself.  Place your fingers as shown in the picture to the left.  Clench your teeth so you can feel the muscles bulge.

Apply deep pressure on just one side for 5 seconds. Then release that pressure and apply deep pressure to the opposite side for 5 seconds. Go back and forth until it doesn’t hurt anymore.  Then find a different “hot spot,” and repeat.  Continue doing this until you can’t find any more tender points on your muscle and jaw.

To stretch the masseter muscle, just press deeply into the original point on the muscle pain free living book coverand slowly open your mouth wide.

Hopefully, you can now see the connection between stress and jaw pain.  Stress is a killer, and is the cause for pain all over your body.  It’s also important to find the cause of stress and do all that is necessary to resolve it.

My book, “Treat Yourself to Pain-Free Living,” will show you how to self-treat painful spasms throughout your body.  Don’t let the pain caused by stress stop you in your tracks. You can become pain-free, and then go and enjoy a yoga class to release stress from your life.

Wishing you well,

Julie Donnelly

julie donnelly

About The Author

Julie Donnelly is a Deep Muscle Massage Therapist with 20 years of experience specializing in the treatment of chronic joint pain and sports injuries. She has worked extensively with elite athletes and patients who have been unsuccessful at finding relief through the more conventional therapies.

She has been widely published, both on – and off – line, in magazines, newsletters, and newspapers around the country. She is also often chosen to speak at national conventions, medical schools, and health facilities nationwide.

These statements have not been evaluated by the Food and Drug Administration. This information is not intended to diagnose, treat, cure or prevent any disease.

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