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Soy - To Fear or to Feast?

November 24, 2018

I get asked ALL THE TIME - 'Is soy dangerous?'


Some people may be concerned about soy products and isoflavones/phytoestrogens - the possibility that the plant-based dietary oestrogen's could cause increased rates of malignancy


So I conferred with health colleagues and looked into the research regarding soy and phytoestrogens. 

I get it. I understand why people are afraid. Cancer is terrible and incredibly devastating. 

Having diagnosed cancer 100's of times on PET-Scans, on CAT scans, in the emergency department, and as a general hospital doctor, I can understand why people may want to avoid anything that may increase their risk of developing a malignancy. 

However, in the following research articles, including a very large literature review written by a Toxicologist and Food safety Researcher - multiple evidence based sources concluded that soy was associated with reduced rates of malignancy, cardiovascular disease, and menopausal symptoms.


Below are a collection of research articles and medical professional opinions on the topic. 


Big names who have written articles about soy include: 

- Dr. Neal Barnard

- Dr. Michael Greger

- Professor Ivonne Rietjens (PhD, Toxicologist and Food Safety Board Advisor)

- The Physicians Committee


Check out their articles below:


1. An article, "There’s no debate: Soy is beneficial to your health" by Dr. Neal Barnard (2016):
There’s no debate: Soy is beneficial to your health. Soy products have been shown beneficial for lung cancer prevention and survival, prostate cancer prevention, heart health and diabetes, bone health, inflammation, and hot flashes, among other conditions. 
 Soy is also beneficial in reducing breast cancer risk and in breast cancer survival. Xiao Ou Shu, M.D., M.P.H., Ph.D., who established the Shanghai Breast Cancer Survival Study, a cohort of more than 5,000 breast cancer survivors and who has also led several other epidemiological studies on soy food and breast cancer risk, will discuss the influence of soy food consumption on breast cancer risk and survival at this summer’s International Conference on Nutrition in Medicine.



2. Large Literature Review by Ivonne Rietjens et al (2017), published in the journal of Pharmacology, "Effects of phytoestrogens on breast cancer":

The use of soy‐based preparations has been proposed for the prevention and treatment of certain types of cancer, such as for the prevention and treatment of breast cancer in women and prostate cancer in men (Eisenbrand et al., 2007). 
Meta‐analyses of epidemiological studies conducted in women consuming high‐soy diets concluded that there is a significant trend of decreased risk for breast cancer upon increasing intake of soy food (Trock et al., 2006; Wu et al., 2008; Dong and Qin, 2011; Chen et al., 2014). High lignan exposure has also been associated with a reduced breast cancer risk in postmenopausal women (Velentzis et al., 2009; Buck et al., 2010). Fritz et al. (2013) reported a systematic review and meta‐analysis on the potential effects of soy, red clover and isoflavone intake on breast cancer incidence and recurrence. The analysis included 40 randomized controlled trials, 11 uncontrolled trials and 80 observational studies. The authors concluded that soy consumption may be associated with reduced risk of breast cancer incidence, recurrence and mortality. Soy intake consistent with a traditional Japanese diet (2–3 servings a day containing 25–50 mg isoflavones) may also be protective against breast cancer and recurrence."
Effects in Cardiovascular disease:
"Oestrogens have been shown to influence atherosclerosis and the related clinical events in a differential way (Rossouw et al., 2007; Cano et al., 2010). They may act not only as protectors against atherosclerosis but also as potential disruptors of established atherosclerotic plaques, the latter being important hallmarks in the pathogenesis of the arterial forms of cardiovascular disease. The concept that phytoestrogens may act in a similar way comes from the observation that in Asian populations with high levels of their consumption, the prevalence of cardiovascular disease is lower than in populations in Western countries (Gonzalez Canete and Duran Aguero, 2014).
"One study concluded that high isoflavone intake was associated with reduced risk of cerebral and myocardial infarctions in Japanese women, with the risk reduction being especially pronounced in postmenopausal women (Kokubo et al., 2007).



3: Soy & Breast Cancer: an update Written By Michael Greger M.D. FACLM on August 29th, 2011:


"We’ve known that regular soy consumption appears to both prevent breast cancer—the number one cancer killer of young women—and prolong survival in women battling the dreaded disease, but we haven’t understood why.
Soybeans naturally contain weakly estrogenic compounds called phytoestrogens (derived from phyton, the Greek word for “plant”). So the original theory was that the regular presence of the estrogen look-alikes in our bloodstream might trick our body into ramping down actual estrogen production as part of a negative feedback loop, like a thermostat that shuts off the heat when it senses it’s getting too warm.
This theory gained empirical support in 2006 when a group of British researchers showed that indeed the presence of phytoestrogens could effectively down-regulate the enzyme that human cells use to make estrogen (at least in a test tube). The theory fell into disfavor, however, when researchers subsequently failed to show that women who consumed soy ended up with less estrogen circulating in their bloodstream. From a breast cancer standpoint, though, we don’t care how much is in the blood, but how much is in the breast.
A new study just published this month measured estrogen levels inside the breasts themselves of women placed on a high versus low soy diet. This was accomplished by aspirating ductal fluid from the nipple, which is what bathes the very cells most likely to turn cancerous. After 6 months, the researchers found a trend towards lower estrogen levels inside the breasts of women eating two servings of soy foods a day. Not only does this aid our understanding of why soy may shield us from cancer, but can help explain the findings presented in today’s new video-of-the-day, which documents new research suggesting young girls drinking soymilk just twice a week may be protected against premature puberty."


4: The Physicians Committee, "Soy and Your Health - Cancer Prevention and Survival", http://www.pcrm.org/health/health-topics/soy-and-your-health:

Epidemiological studies have found that soy protein may reduce the risk for cancers including breast, colon, and prostate.1

Studies show that women who include soy products in their routine are less likely to develop breast cancer, compared with other women. In January 2008, researchers at the University of Southern California found that women averaging one cup of soymilk or about one-half cup of tofu daily have about 30 percent less risk of developing breast cancer, compared with women who have little or no soy products in their diets.2 However, to be effective, the soy consumption may have to occur early in life, as breast tissue is forming during adolescence.3,4

What about women who have been previously diagnosed with breast cancer? The Women’s Healthy Eating and Living Study showed that women previously diagnosed with breast cancer gain a major advantage by incorporating soy products into their diets. Those who consumed the most soy products cut their risk of cancer recurrence or mortality in half. Similarly, a study in the Journal of the American Medical Association reported results based on 5,042 women previously diagnosed with breast cancer who were participating in the Shanghai Breast Cancer Survival Study over a four-year period. The study showed that women who regularly consumed soy products, such as soymilk, tofu, or edamame, had a 32 percent lower risk of recurrence and a 29 percent decreased risk of death, compared with women who consumed little or no soy.5 Meanwhile, a study at Kaiser Permanente suggested much the same thing. Women who avoid soy products get no advantage at all. Those who include soy products in their diets appear to cut their risk of cancer recurrence.6

A 2012 analysis that combined the results of prior studies, including a total of 9,514 women from the United States and China, showed that those who consumed the most soy products were 25 percent less likely to have their cancer return, compared with those who tended to avoid soy products.7 Other studies, including the Women’s Healthy Eating and Living Study, have found that there was no effect or a favorable effect on breast tissue density in breast cancer survivors consuming soy, regardless of hormone receptor status.8,9



The medical and/or nutritional information on this website is for educational purposes only and is not intended to be a substitute for professional medical advice, diagnosis, or treatment.

Please seek medical advice before using diet to treat disease.

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