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Does Soy Cause Breast Cancer

It May Cause Chronic Inflammation

Does Soy Cause Cancer?

For years, the popular additive and cooking oil was considered a better alternative to health-harming saturated fats, but new research suggests that when it comes to weight gain, soybean oil may be just as bad. Our bodies evolved on a near equal balance of omega-6 fatty acids and omega-3 fatty acids however, over the last century, our diets have shifted completely to omega-6s. In fact, according to a study in Nutrients, most Americans are getting 20 times the amount of omega-6s than we really needa big problem considering omega-6s are inflammation-causing, fat-storing, and weight-gain-inducing whereas omega-3s are anti-inflammatory. One of the primary causes for this shift? High consumption of foods that have been fried in soybean oil, which has an omega-6 to omega-3 ratio of 7.5:1.

Checking For Risk Of Breast Cancer Recurrence

After an average of nine years after their breast cancer diagnosis, women who consumed the highest amount of soy, or more than 23 milligrams of soy per day, had a 9% lower risk of dying from any cause and a 15% reduced risk for breastcancer recurrence, compared to women who consumed 0.48 milligrams of soy per day or less.

These results were not considered statistically significant and therefore may be due to chance.

According to Shu, 23 milligrams per day of soy consumed is the equivalent of one glass of soy milk or a half cup of tofu.

Leif Ellisen, MD, PhD, of the Gillette Center for Breast Cancer at the Massachusetts General Hospital Cancer Center in Boston, says women often ask him whether soy is safe after breast cancer.

âThere are a lot of health benefits in soy, but there has been some theoretical concern that soy has molecules that resemble estrogen which may increase risk of breast cancer recurrence,â he says.

But ârather than any negative effect, this study suggested a benefit for these patients in terms of overall health and breast cancer recurrence,â he says. âThis is quite reassuring for women who were concerned that they might have to eliminate healthy soy foods from their diets.â

Dietary Soy Versus Soy Supplements

The isoflavones found in soybeans, sesame seeds, and legumes are about one hundredth as powerful as natural female estrogens. If you’re getting your isoflavones from dietary sources, you’d have a hard time overdosing yourself, unless you went on an all-soy diet. So wouldn’t those capsules containing soy isoflavones that are sold as hormonal support and bone health protection be safe? The answer is: it depends and we don’t really know at this time. Pills with isolated soy isoflavones may cause troublenot enough research has been done yet on people to determine whether or not high concentrations of those isoflavones may encourage the growth of breast cancer. If you’re taking soy supplements for menopausal symptoms, speak with your healthcare provider about what level of isoflavones may be safe for you.

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It May Block Protein Digestion

Soy is like that date who demands affection while refusing PDA and cuddling. Even though soy is packed with lean protein, it’s also packed with trypsin and protease inhibitorsenzymes that make the digestion of protein incredibly difficult, causing some gastric distress along with a deficiency in amino acid uptake if soy is eaten in excess. The only way to destroy these anti-nutrients is by soaking and cooking the beans.

Fermented Soy Will Heal Your Gut

Does Soy Really Decrease the Risk of Breast Cancer?

Toss the fart-y processed tofu and veggie burgers, and stick to fermented varieties like tempeh, miso, and natto, which are easier to digest. Smith explains that Fermented soy is generally thought of as better than regular soy because the fermenting process reduces anti-nutrients, such as phytic acid and sapoinin, and also because isoflavones are thought to be more available for our bodies to use in this form. Not to mention fermented foods are also a great source of gut-healthy probiotics which can promote healthy digestion. Natto, in particular, is touted for its unique benefits due to its high levels of vitamin K2which is important for cardiovascular and bone healthas well as the presence of nattokinase, an enzyme found in the fermented food which has been shown to dissolve blood clots.

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Higher Concentrations Of Isoflavones In Mouse Studies

Because of the differences in how soy isoflavones are metabolized in mice and humans, the mice in these were exposed to much higher concentrations of isoflavones than the amounts human beings typically eat. Researchers have concluded that the higher concentrations mean the outcomes are likely to be different for the two species.

When researchers conducted similar soy , whose biology is much closer to human biology, they found no increased risk of breast cancer among the primates who consumed soy.

What Human Studies Show

A number of long-term studies involving human populations have shown that eating soy foods does not increase the risk of breast cancer. On the contrary: Studies show that diets rich in soy may actually help to protect you from developing breast cancer.

A 2020 study that tracked the soy consumption of over 300,000 women in China found that moderate soy consumption did not raise the risk of breast cancer for women in the study. Women in the study who reported eating higher amounts of soy products experienced a lower risk of breast cancer.

A 2020 meta-analysis evaluated the results of 18 separate studies. After evaluating the results of these studies, researchers concluded that higher amounts of soy in the diet lowered the breast cancer risk for women. The protective effect was highest for women who had not yet reached menopause.

American Cancer Society say soy foods are safe and healthy for people to eat. They caution, however, that more research needs to be done to see whether taking isoflavone supplements is equally safe, since these supplements may have higher concentrations of isoflavones than there are in soy foods.

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Differences In How Soy Is Processed

First, mice process the soy differently than humans do. To understand how, a little background is necessary. Soy contains several kinds of phytoestrogens . Phytoestrogens are plant-based substances that act like estrogen in the body.

According to the American Cancer Society , certain types of breast cancer have been traced to increased estrogen in the body. Thats what gave researchers cause for concern about soy and breast cancer. However, in humans, phytoestrogens turn into genistein and daidzein, two isoflavones that are very different from and much weaker than human estrogen.

In fact, soy has been proven to in tissues. In tissues with breast cancer cells, estrogen stimulates the multiplication of cancer cells. When soy blocks this stronger form of estrogen, it is playing an active role in reducing the risk of breast cancer.

Systematic Review And Doseresponse Meta

Mayo Clinic Minute: Does Soy Increase Breast Cancer Risk?

We searched on PubMed, Embase and Cochrane library from their dates of inception to March 2019 for prospective studies examining the association between soy intake and breast cancer. Studies using concentrations of isoflavones or their metabolites in biological samples were not included owing to the difficulty in converting biological concentration into amount of soy isoflavone intake. However, we believed that this had no great impact on the result because studies using biological concentrations as exposure assessment were mainly conducted among populations with pretty low level of soy intake . We excluded studies if the amount of soy intake was unavailable and could not be estimated using relevant data. We also excluded reviews, non-human studies, abstract-only publications or editorials. If the same cohort study published more than one original articles on soy intake and breast cancer, the paper reporting the largest sample size, longest follow-up time, or the widest variation in soy intake levels was kept. In addition, studies in which participants soy intake levels were very low were not included in the quantitative synthesis as the weights contributed by these studies were negligible. Detailed literature searching strategy, data extraction methods, and quality assessment of individual study were presented in Appendix.

All statistical analyses were performed with Stata . All P values were two-sided and statistical significance was defined as P< 0.05.

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It Can Prevent Postmenopausal Symptoms

Hot flashes are no fun. Studies link the debilitating symptoms of peri- and postmenopause to declining levels of estrogen. And according to a review of 16 studies published in the British Journal of Clinical Pharmacology, soy isoflavones can aid with your menopause symptomsalbeit they only provide half of the maximum effect and work 10 weeks slower than traditional hormone replacement therapy drug, estradiol, in terms of reducing hot flash frequency. Isoflavones are a class of phytoestrogens, plant versions of human estrogen. In other words, they nearly mimic estrogen’s structure, allowing them to function in the same estrogen pathways which can help relieve hot flash symptoms. Chickpeas also contain phytoestrogen, which makes them one of the healthiest foods for women.

Lower Risk Of Recurrence

What about women who have been diagnosed with breast cancer? Researchers found that women diagnosed with estrogen-negative breast cancer who ate the most soy isoflavones had a 21% lower risk of dying from cancer compared with those who ate the least.

The Womens Healthy Eating and Living Study also showed that soy may help protect breast cancer survivors. Researchers found that women who ate the most soy cut their risk of cancer coming back or cancer death in half. Another study followed 5,042 women previously diagnosed with breast cancer for four years. Women who regularly consumed soy products like soy milk, tofu, or edamame came out ahead. They were about a third less likely to have their cancer come back, and 29% less likely to die from cancer compared with women who ate little soy. Numerous other studies confirm these findings. Women who avoid soy get no advantage, while women who consume soy are less likely to have their cancer return.

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Straight Talk About Soy

The Takeaway: Soy is a unique food that is widely studied for its estrogenic and anti-estrogenic effects on the body. Studies may seem to present conflicting conclusions about soy, but this is largely due to the wide variation in how soy is studied. Results of recent population studies suggest that soy has either a beneficial or neutral effect on various health conditions. Soy is a nutrient-dense source of protein that can safely be consumed several times a week, and probably more often, and is likely to provide health benefitsespecially when eaten as an alternative to red and processed meat.

Soy is exalted as a health food by some, with claims of taming hot flashes, warding off osteoporosis, and protecting against hormonal cancers like breast and prostate.

At the same time, soy is shunned by others for fear that it may cause breast cancer, thyroid problems, and dementia, though these claims have not been substantiated.

Whether published in a popular press article or a well-designed clinical study, some debate about soy remains. As a species within the legume family, nutrition scientists often label soy as a food with potential for significant health benefits. However, due to contrary research that suggests possible negative effects of soy in certain situations, there has been a hesitancy to wholeheartedly promote soy.

Thus, there are many factors that make it difficult to construct blanket statements about the health effects of soy.

Unfermented soy foods

Research On Soy And Disease

Is Soy Healthy for Breast Cancer Survivors?

Learn more about the research on soy and specific diseases or other conditions:

Soy protein took center stage after research showed that it might lower levels of harmful cholesterol. A 1995 meta-analysis of 38 controlled clinical trials showed that eating approximately 50 grams of soy protein a day in place of animal protein reduced harmful LDL cholesterol by 12.9 percent. Such reductions, if sustained over time, could mean a greater than 20% lower risk of heart attack, stroke, or other forms of cardiovascular disease. In response to this finding, in 1999 the Food and Drug Administration allowed companies to claim that diets low in saturated fat and cholesterol that also contain soy may reduce the risk of heart disease.

However, a number of studies since have tempered that finding. According to a comprehensive update of soy research by the nutrition committee of the American Heart Association published in 2000, eating 50 grams of soy per day lowered LDL by only about 3%. In October 2017, after review of additional scientific studies since the health claim was authorized, the FDA proposed a rule to revoke the claim because numerous studies presented inconsistent findings on the relationship between soy protein and heart disease. Some of these inconsistencies may have resulted because soy was compared with a variety of alternative foods.

Another prospective study followed 1,954 American women who were breast cancer survivors for six years. Key highlights of the study:

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Is It Safe For Survivors

Studies of pre- and post-menopausal women suggest soy isoflavones may have a protective effect against breast cancer. Population studies indicate that soy consumption in survivors of breast cancer may be linked to decreased recurrence and greater overall survival. A 2017 study looked at more than 6,200 American and Canadian women with breast cancer. These women filled out surveys about what they ate and other lifestyle habits. Those women who ate the highest amounts of isoflavones had a 21% lower risk of having died from any cause, compared to the women who ate the lowest amount of isoflavones.

It Will Help Strengthen Your Bones

Many soyfoods are good non-dairy sources of calcium, which is particularly important in aging populations who become increasingly lactose-intolerant. This mineral is essential for maintaining bone health and preventing both osteoporosis and cancer. Just a half a cup of tofu provides you with 43 percent of your DV. And even though one cup of edamame serves up 9 percent of your DV of calcium, this form of soy may still possess high levels of phytates, which could prevent your body’s absorption of this mineral.

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You’ll Probably Be Exposed To Carcinogens

Smith tells us that the major concern with soy products is that they’re so over-produced and over-processedand the numbers certainly back her up. An astounding 94 percent of soybeans are genetically engineered in the US, according to the Center for Food Safety, which makes it the number one GM crop plant in the world. The issue here is that almost all genetically modified soybeans are designed to be “Roundup ready” . And after the FDA classified the main active ingredient in Roundup, glyphosate, as “probably carcinogenic to humans,” this means some seriously bad news for your health.

According to a study published in Food Chemistry, researchers found that genetically engineered soybeans accumulate and absorb high levels of glyphosate upon being sprayed during their growing seasonthey also have poorer nutritional profiles compared to organic soybeans. And even though the maximum residue level in the US is 20 mg/kg, countless studies in animals and using human cells have found serious negative health effects at concentrations far below the MRLs, including causing miscarriages and abnormal fetal development by interfering with hormone productions.

Is Soy Safe For A Person With Breast Cancer

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The consensus is that a person who has a diagnosis of breast cancer can safely consume soy products.

Products containing soy as a food additive in the form of soy lecithin and soy oil are also generally safe for people living with breast cancer. These products do not contain any phytoestrogen.

However, the Dana-Farber Cancer Institute points out that many doctors recommend that people with hormone-sensitive cancer minimize their intake of soy protein powder supplements or soy protein isolate.

Anyone who is considering making significant changes to their diet should speak with a doctor before doing so.

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Should Cancer Patients Avoid Soy

Do soy foods increase your cancer risk? April marks National Soy Foods Month, so lets explore that question.

According to historical documents and archaeological finds, soybeans were first cultivated sometime in the 11th century BC in the eastern half of northern China, and soy has remained an important part of Asian diets ever since. Soy was first introduced to the United States in the mid-1700s. These days, soy sometimes gets a bad rap, but it can be part of a healthy pattern of eating.

If You Have Breast Cancer

In 2017 , the Breast Cancer Family Registry followed the intake of soy isoflavones for 6,235 women diagnosed with breast cancer and living in the U.S. and Canada. It was found that women who ate the highest amounts of soy isoflavones had a 21 percent lower risk of death compared with women with the lowest intakes.

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Eating Soy May Turn On Genes Linked To Cancer Growth

Soybeans are the most widely used, least expensive, and least caloric way to get large amounts of protein. You can eat soybeans in many forms, including tofu, the beans themselves , soy milk, miso, and soy powder.

Soy foods have a lot of isoflavones, which are weak estrogen-like compounds found in plants. Because estrogen can promote the development, growth, and spread of breast cancers, doctors have worried that eating a lot of soy foods or soy isoflavones might worsen the prognosis of women diagnosed with breast cancer.

While past research results have been mixed, a small study done by researchers at the Memorial Sloan Kettering Cancer Center and Weill Cornell Medical College suggests that for some women, adding a medium amount of soy to their diets turns on genes that can cause cancer to grow.

The research was published in the Sept. 4, 2014 issue of the Journal of the National Cancer Institute. Read the abstract of The Effects of Soy Supplementation on Gene Expression in Breast Cancer: A Randomized Placebo-Controlled Study.

During those 2 to 3 weeks, the women were randomly assigned to receive either:

  • soy protein
  • a placebo that looked like the soy protein

The study also didnt look at:


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