Phytoestrogens: Benefits vs. Negatives, Top Foods - Dr. Axe

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Are Phytoestrogens Good or Bad for You? Separating Fact from Fiction


Phytoestrogens - Dr. Axe

Phytoestrogens, or plant-based estrogens, are an almost mysterious part of nutrition. Just like it’s hard to tell if soy is bad for you or not, sometimes phytoestrogens are bad for you, and other times they can fight certain cancers!

To illustrate just how confusing phytoestrogens are, there are countless studies that show they can, in fact, fight and inhibit breast cancer … while at the same time, research out of Canada warns that low concentrations of certain phytoestrogens actually promote breast cancer tumor growth and inhibit certain drugs that treat the disease! No wonder they’re so difficult to wrap our heads around!

Their effects are controversial, and research, at first glance, even seems to conflict. However, understanding the role of phytoestrogens in your health is a key part to maintaining proper hormone levels throughout your life. So are phytoestrogens good or bad for you? Do they contribute to the estrogen epidemic or not? Let’s separate the fact from the fiction and look at the positives and negatives of these controversial plant estrogens.

What Are Phytoestrogens?

The word phytoestrogens comes from the Greek word “phyto,” or plant, and “estrogen,” the hormone that causes fertility in all female mammals. Phytoestrogens have also been termed dietary estrogens because they’re not created by the human endocrine system. They can only be ingested or consumed.

A similar class of non-endocrine estrogens is xenoestrogens, synthetic estrogens found in certain kinds of plastic and pesticide products. While I deal primarily with a discussion on phytoestrogens in this article, it’s important to consider the combination and interaction of all of the environmental estrogens you encounter.


In their natural state, phytoestrogens exist within plants as a natural defense against herbivores. Plants secrete these hormones to modulate the fertility of animals that may eat them to reduce further attacks. (1)

Soy is known as the most phytoestrogen-rich plant found in a typical Western diet. Although it was initially considered a superfood, the real story with soy is that it’s usually something to avoid. I’ll talk more about soy in a moment, but first, let’s talk a little more about what phytoestrogens are.

Part of what makes phytoestrogens a bit tricky is their ability to both mimic estrogen and act as an estrogen antagonist (meaning they behave in the opposite way of biological estrogen). They affect the body by attaching to estrogen receptors. Because they aren’t specifically necessary for a human diet, phytoestrogens can’t be considered actual nutrients. The most well-studied of the types of phytoestrogen compounds are isoflavones, also commonly referred to as soy isoflavones because most are found in soy and red clover.

The estrogenic and anti-estrogenic effects of phytoestrogens have often been thought of as overwhelmingly negative. For the majority of young women, extra estrogen in the body can lead to infertility, polycystic ovarian syndrome and even certain types of cancer. Men generally don’t need extra estrogen in their systems, either. However, in the case of women over the age of 50 experiencing decreased estrogen levels, extra estrogen can decrease cancer risk, among other benefits.

Health Benefits

Don’t fear! The research surrounding phytoestrogens isn’t all bad. While I encourage you to consult with your physician before making any major diet changes, for certain people (generally, women over 50), phytoestrogens can actually benefit you!

1. May Reduce or Prevent Certain Types of Cancers

Cancers related to hormone production can be treated, in part, by adjusting the hormone levels in the body by eating the right foods. Phytoestrogens have been studied extensively in connection with breast and ovarian cancers, with many positive results showing they can actually be natural cancer treatments for some.

A 2009 study of over 5,000 women diagnosed with breast cancer showed a significant decrease in death and recurrence of the disease of the patients on a diet rich in non-soy phytoestrogens, a finding that echoed a 1997 questionnaire study of breast cancer patients. (2, 3) Another project, spanning nine years and following 800 women, showed a 54 percent decrease in the occurrence of endometrial cancer in women eating a diet high in phytoestrogens. (4)

Regarding breast cancer in particular, it seems that apigenin might be the best of the phytoestrogens in reducing breast cancer cell growth. (5)

The jury is still out on exactly how and when phytoestrogens are most efficient in fighting hormonal cancers. Depending on the state of menopause, individual body makeup and the times at which high levels of soy are part of one’s diet, phytoestrogens may or may not be beneficial for cancer prevention and/or treatment. (6,7)

2. Enhance Heart Health

OK, they may not make you feel all warm and fuzzy inside, but phytoestrogens are proven to improve heart health, specifically in postmenopausal women. They can be used to treat arteriosclerosis, a disease characterized by fatty buildup within the arteries, and seem to do so by regulating many different hormone and chemical levels within the body. (8)

3. Improve Health During Menopause

Yes, it’s important to limit intake of phytoestrogen-rich foods and avoid high-estrogen foods during most someone’s life. However, a large variety of studies has proved these dietary estrogens actually help some women during menopause.

Menopause is the period of time in which a women transitions from her last menstrual cycle, ending fertility. While childbearing potential ends, menopause doesn’t have to mark the end of vitality and healthy sexuality. The biggest drawback to menopause is the unpredictable change in sex hormone levels, namely estrogen, progesterone and testosterone.

During perimenopause, some physicians suggest beginning to increase phytoestrogen intake to counteract the effects of the hormonal imbalances women begin to experience and balance hormones naturally. Some research indicates a drastic drop it in hot flashes for women in perimenopause eating a phytoestrogen-rich diet.

Another benefit phytoestrogens may offer to menopausal or postmenopausal women is a reduction in bone loss, leading to higher bone density and fewer breaks, when administered in dose-specific measures alongside vitamin D. (9) They’ve also been shown to regulate iron absorption into the bloodstream, offering mild anti-inflammatory effects and protecting against massive iron level fluctuations. (10)

As of yet, there is not sufficient evidence to suggest a phytoestrogen-rich menopause diet can totally counter and relieve menopause symptoms, but nothing truly can. The symptoms of this hormonal change can be managed but not completely avoided. I do recommend looking into natural alternatives to dangerous hormone replacement therapy.


4. Help with Weight Loss

The phytoestrogen genistein is highlighted in a study to determine the effects of phytoestrogens on obesity. Due to its various effects, genistein seems to have the ability to regulate obesity, although the reasons why are unclear. (11)

This weight loss benefit requires more research to draw specific conclusions, but the findings are encouraging. Of course, the best defense against obesity is a healthy, balanced diet and an active lifestyle.

5. Boost Libido

Yes, you read that right! Some reports suggest that phytoestrogens, specifically in beer, may delay ejaculation and increase libido. While too much of a good thing isn’t — well — good, the mild estrogenic effects of phytoestrogens from hops, bourbon and beer in the male body seem to increase the time you have to please your partner. (12)

However, remember that excessive phytoestrogen intake over time is not advisable for men — moderation is key.

Phytoestrogens positives and negatives - Dr. Axe

Negative Effects

While research supports these benefits described above, there are negative effects of phytoestrogens as well, of which you should be aware. These issues are mainly related to fertility and development. It’s also important to note that many of these studies delve into the effects of phytoestrogens in soy, which contains its own problematic issues.

1. Can Adversely Affect Fertility

Studies show that diets rich in certain phytoestrogens reduce the occurrence of pregnancies in humans, California quail, deer mice, Australian sheep and cheetahs. In some of these examples, the removal of phytoestrogens from the diet caused fertility levels to rebalance.

In addition, exposure to genistein and coumestrol, two specific phytoestrogen compounds, early in life may contribute to fertility issues later in development. They may cause decreased sperm levels, but this remains unclear throughout different research studies. (13, 14)

2. May Lead to Hormonal Issues

One particular area of concern is the appearance of plant-based estrogens in soy infant formulas, as the long-term consequences are still not well-understood. However, some research indicates possible negative correlations, including a higher occurrence of boys born with hypospadias, increased use of allergy medicines, and more severe menstrual bleeding and cramps for girls. Again, genistein was identified as the most likely culprit.

As with much of the information about phytoestrogens, there are conflicting ideas about whether or not they’re harmful in the long run. At least one study found no significant difference in people fed soy formula versus those fed with cow’s milk, so more research is still needed to make any firm conclusions. (15)

3. Potentially Stimulate Breast Cancer Growth

As I’ve already mentioned, phytoestrogens have the ability to inhibit the growth of certain cancers, such as breast cancer. However, a fascinating study out of Canada found that low concentrations of phytoestrogens actually may make breast cancers grow faster, as well as inhibit the effects of tamoxifen, the drug used to treat late-stage breast cancer.

In higher concentrations, the effect was the opposite, causing tumors to shrink and magnifying the impact of the drugs — showing just how complicated phytoestrogens really are. (16)

4. Increase Risk of Cognitive Decline and Dementia

Another concern to be aware of is the possibility of mental decline in connection with consuming a lot of phytoestrogens. While the evidence remains inconclusive, research suggests a link between dementia and cognitive decline with phytoestrogen intake.

The factors that may cause this decline vary, depending on age and thyroid health, but it’s important to take good care of your brain — it’s the only one you’ve got! Don’t go overboard with phytoestrogen intake, especially if you might be at risk for cognitive disorders like dementia. (17)

Top Foods

Phytoestrogens exist in many foods, supplements and essential oils. Some of the highest concentrations can be found in (18):

  • Soybeans and soy products
  • Tempeh
  • Flaxseeds
  • Oats
  • Barley
  • Lentils
  • Sesame seeds
  • Yams
  • Alfalfa
  • Apples
  • Carrots
  • Jasmine oil
  • Pomegranates
  • Wheat germ
  • Coffee
  • Licorice root
  • Hops
  • Bourbon
  • Beer
  • Red clover
  • Clary sage oil
Phytoestrogens foods - Dr. Axe

All Soy Is Not Created Equal

As soy is the most concentrated source of phytoestrogens for the typical American, it’s important to examine the safety of soy itself — a subject debated quite a bit. So, is soy bad for you or good for you?

The answer is not a simple “yes” or “no.” It’s more complex. The difficulty of understanding the effects of soy is caused mainly by the form of available soy in the U.S. There is soy to eat and soy to avoid — and unfortunately, most soy in the U.S. falls into the latter category.

In Japan, one of the healthiest places on Earth, soy is a prevalent staple. However, the soy there is not genetically modified. That used to be the case in the U.S. as well. In 1997, only 8 percent of soy was genetically modified. As of 2010, about 93 percent of the soy in the U.S. was genetically modified — and that’s definitely not something you want to have in your body.

Another factor in the soy discussion is unfermented versus fermented soy. Unfermented soy contains a laundry list of nasty things you should avoid. Fermented soy, on the other hand, is a great probiotic food.

I advocate the removal of all soy milk, soy protein and most other forms of soy from your diet. The exception I generally make is for soy lecithin, a fermented soy product that has several health benefits.

Remember, if you’re a woman entering or going through menopause and may benefit from phytoestrogens in your diet, soy is not the only source.

The Dangers of Endocrine Disruptors

By now, you’ve probably heard of endocrine disruptors — synthetic or non-human hormones we’re exposed to or ingest that mess with our hormones. Some disruptors are more harmful than others. For example, the xenoestrogens in plastics, such as medicine bottles, are some of the worst for the balance of hormones in your body.

Phytoestrogens are weak estrogens in comparison to xenoestrogens or the biological estrogen the human body produces. They may not be as unsafe as other endocrine disruptors, but they should be considered generally undesirable for men and younger women, especially those who have issues with estrogen dominance.

But what are endocrine disruptors (ED)? I discuss it in detail in the link above, but in short, EDs are chemicals and natural compounds that interrupt hormonal balance in the body and may cause a host of health problems, especially when they build up over time. (19) The most prevalent appearance of EDs are chemicals found in plastics and pesticides, but they can also be found in the form of phytoestrogens, progestin (progesterone-mimickers) and even in many cosmetics.

The hormonal imbalances caused by these sneaky disruptors have led to an overall drop in the average age of puberty and may also contribute to various fertility issues, such as low sperm counts, endometriosis, and ovarian or testicular cancer.

Two of the best protections against a buildup of endocrine disruptors in your body are a diet full of organic, non-GMO foods and a lifestyle avoiding harsh chemicals wherever possible, such as in makeup or pesticides. The more you’re exposed to these disruptors — such as phytoestrogens — over the course of your life, the higher the likelihood that you will experience negative reactions.

One good way to modulate the impact of phytoestrogens in particular is to pair them with phyto-progestins (progestins specifically found in plants). Clary sage oil is an example of a source of both phytoestrogens and phyto-progestins, which balance the effects of one another and help protect your body against too much of one reproductive hormone.

Final Thoughts

As we’ve seen, phytoestrogens are not easily put into the healthy or unhealthy category. The truth of the matter is they can be beneficial in doses, particularly for women of menopausal age, but they also have adverse side effects, particularly for men.

As endocrine disruptors, your best bet is to limit your intake overall and consult with your doctor before deciding to either add more phytoestrogens into your diet or cutting them out completely.

One thing is for sure, however: You’re better off avoiding soy as your phytoestrogens source, instead opting for healthier, more nutritious options like essential oils and certain vegetables. The debate rages on in the research community, but if you keep these facts about phytoestrogens top of mind, you can optimize their benefits while limiting their negative side effects.

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