{"id":5326,"date":"2025-10-01T23:57:05","date_gmt":"2025-10-02T03:57:05","guid":{"rendered":"https:\/\/www.chaneyhealth.com\/healthtips\/?p=5326"},"modified":"2025-10-01T23:57:05","modified_gmt":"2025-10-02T03:57:05","slug":"the-soy-myth","status":"publish","type":"post","link":"https:\/\/www.chaneyhealth.com\/healthtips\/the-soy-myth\/","title":{"rendered":"The Soy Myth"},"content":{"rendered":"

Why Is There So Much Confusion About Soy?<\/strong><\/span><\/h2>\n

Author: Dr. Stephen Chaney<\/strong><\/p>\n

\"soy\"<\/a>What is the truth about soy and breast cancer? Does it increase the risk of breast cancer, or is that just a myth? If you are a woman, particularly a woman with breast cancer, it is an important question.<\/p>\n

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. Who is right?<\/p>\n

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.<\/p>\n

Why Is There So Much Confusion About Soy?<\/strong><\/span><\/h2>\n

\"Questioning<\/a>Soy 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.<\/p>\n

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.<\/p>\n

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 decrease breast cancer risk.<\/p>\n

The confusion has been amplified by claims and counterclaims 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.<\/p>\n

Their blogs claim that soy definitely increases breast cancer risk and should be avoided at all costs. Their claims have been picked up by other web sites and blogs. Eventually, the claims have been repeated so many times that people started to believe them. A \u201cmyth\u201d has been created. I call it a myth because it was never based on convincing scientific evidence.<\/p>\n

In the meantime, scientists looked at the cell culture and animal studies and took a more responsible approach. They said \u201cIf this is true, it is an important public health issue. We need to do clinical trials in humans to test this hypothesis.\u201d<\/p>\n

What Have Previous Clinical Studies Shown?<\/strong><\/span><\/h2>\n

\"breast<\/a>The question of whether soy consumption increased the risk of developing breast cancer 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<\/a>). None of those studies found any evidence that soy increased the risk of breast cancer.<\/p>\n

What about recurrence of breast cancer in women who are breast cancer survivors? There have been five major clinical studie<\/a><\/span>s 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 urvivors.<\/p>\n

A meta-analysis of all 5 studies was published in 2013 (Chi et al, Asian Pac J Cancer Prev., 14: 2407-2412, 2013<\/a><\/span>). 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.<\/p>\n

What Did The Most Recent Study Show?<\/strong><\/span><\/h2>\n

\"Clinical<\/a>In earlier 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.<\/p>\n

To better evaluate the effect of soy consumption on breast cancer survivors in the North America, a 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<\/a><\/span>).<\/p>\n

The data were collected from The Breast Cancer Family Registry, an international research infrastructure established in 1995. The women enrolled in this registry either have been recently diagnosed with breast cancer or have a family history of breast cancer.<\/p>\n

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.<\/p>\n

The results were as follows:<\/p>\n