Are Phytoestrogens Good For Your Health?

Their benefits are unclear, but they may help the following conditions

flaxseeds are phytoestrogens
Flaxseeds are a source of phytoestrogens. Gil Guelfucci/Moment Open/Getty Images

Phytoestrogens are plant-derived compounds present in foods such as whole grains, leafy greens, beans, soy, and garlic. Research suggests that phytoestrogens may mimic the action of estrogen and therefore may offer the same benefits as the hormone, such as protecting against bone loss and alleviating hot flashes in menopausal women. Phytoestrogens consist of isoflavones (the most well-known), prenylflavinoids, coumestans, and lignans.

 

In alternative medicine, dietary supplements containing phytoestrogens are sometimes used as prevention against hormone-dependent cancers (including some forms of breast cancer), heart disease, osteoporosis, and menopausal symptoms.

However, because phytoestrogens are endocrine disruptors, meaning they interact with and alter your hormones, some researchers raise the concern that their estrogenic properties could cause negative health effects. In fact, to date, phytoestrogens are one of the most controversial topics in the realm of nutrition and women's health. 

So far, studies on the health effects of phytoestrogens have yielded mixed results. Here's a look at several key study findings. 

May Lower Risk of Certain Cancers

Some research shows that consumption of phytoestrogens is associated with a decreased risk of colon, breast, ovarian, prostate, gastrointestinal, and endometrial cancers.

 

In 2016, a review of 17 studies found that soy isoflavone consumption was correlated with a 23% reduction in colorectal cancer risk. 

In 2015, a meta-analysis of 10 studies found that soy intake had a significant protective effect against endometrial cancer. 

In 2014, a review of 40 studies found that soy intake is associated with a slight reduction in gastrointestinal cancer risk.

 

As for breast cancer, some studies show that women in countries with a high consumption of isoflavones, such as the Japanese who eat miso soup frequently, have a reduced risk of breast cancer. Yet, previous studies have shown that phytoestrogens may stimulate the growth of breast tumors. 

May Stall Bone Loss

Some women have used phytoestrogens as an alternative to hormone replacement therapy, or HRT, a treatment approach used to reduce menopausal symptoms and decrease the risk of osteoporosis and cardiovascular disease. 

A 2013 study showed that phytoestrogens may inhibit cells that cause bone loss, and enhance bone formation and bone mineral density. 

A 2012 review of studies showed that soy isoflavone supplements significantly increased bone mineral density in women by 54%. 

However, a 2015 study showed higher rates of low bone mineral density in the lumbar spine and femoral neck among Japenese menopausal women with a higher isoflavone intake. Several researchers have concluded that there is not sufficient evidence to suggest that phytoestrogens improve bone density. 

May Lower Cholesterol 

Several studies have shown that phytoestrogens may lower the risks factors for heart disease. For example, a meta-analysis of studies published in 2011 showed that regular consumption of 1 to 2 servings of soy protein daily significantly reduced serum levels of "bad" cholesterol.

Older studies have shown similar links. 

But a 2016 review published in the British Journal of Pharmacology concluded that isoflavones do not significantly alter lipid levels, and phytoestrogens do not significantly reduce cardiovascular risk—however, lignans, in particular, may improve cardiovascular risk among smokers. 

Sources of Phytoestrogens

Phytoestrogens are present in a number of substances commonly found in dietary supplements, including:

  • Soy. Also found to fight hot flashes and lower cholesterol levels, soy contains phytoestrogen compounds called isoflavones. Preliminary research indicates that soy may also help keep bones strong, as well as slightly decrease the risk of breast cancer.
  • Red CloverAnother source of isoflavones, red clover is an herb often used to ease menopausal symptoms. This phytoestrogen has been found to tame hot flashes, as well as inhibit the loss of bone mineral density during menopause. Findings from preliminary research also suggest that red clover may reduce prostate cancer risk.

Other sources of phytoestrogens include alfalfa, hops, and vitex.

Using Phytoestrogens for Health

Ultimately, there is not enough conclusive evidence that phytoestrogens on their own are powerful enough to improve all these facets of health. And some doctors believe caution should be exercised consuming them due to potential adverse effects. 

For instance, some research suggests that genistein (a phytoestrogen found in soy) may interfere with the actions of tamoxifen (a drug used to treat breast cancer). What's more, people who have (or are at risk for) any type of hormone-sensitive condition may need to avoid phytoestrogens, due to their estrogen-like activity.

If you're considering the use of phytoestrogens in treatment or prevention of any health problem, it's crucial to consult your physician in weighing the potential benefits and risks. Self-treating a condition and avoiding or delaying standard care may have serious consequences.

Sources

 

Zhang GQ, Chen JL, Liu Q, Zhang Y, Zeng H, Zhao Y. Soy Intake Is Associated With Lower Endometrial Cancer Risk: A Systematic Review and Meta-Analysis of Observational Studies. Medicine (Baltimore). 2015 Dec.

Genevieve Tse, Guy D. Eslick. Soy and isoflavone consumption and risk of gastrointestinal cancer: a systematic review and meta-analysis. European Journal of Nutrition. February 2016, Volume 55, Issue 1, pp 63–73.

Yi Yu, Xiaoli Jing, Hui Li, Xiang Zhao, Dongping Wang. Soy isoflavone consumption and colorectal cancer risk: a systematic review and meta-analysis. Scientific Reports, May 2016.

Anderson JW, Bush HM. Soy protein effects on serum lipoproteins: a quality assessment and meta-analysis of randomized, controlled studies. Journal of the American College of Nutrition 2011 Apr;30(2):79-91. 

Wei P, Liu M, Chen Y, Chen DC.  Systematic review of soy isoflavone supplements on osteoporosis in women. Asian Pac J Trop Med. 2012 Mar. 

 

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