Phytoestrogens are natural compounds that exist in many plants and foods, such as dairy, flaxseeds, hops, and soy. These compounds have a similar chemical structure to estrogen.

Estrogen is a hormone that is essential for health in all sexes, although females have higher amounts. It helps keep the bones strong, regulates metabolism, and supports fertility.

Phytoestrogens may have a similar effect on the body to estrogen, which may help those with low estrogen, such as people going through menopause.

However, it is important to note that people have to consistently consume fairly high amounts of phytoestrogens for them to have any measurable effect on the body.

This article explores the health benefits and risks of phytoestrogens. It also lists foods that are high in phytoestrogens.

A note about sex and gender

Sex and gender exist on spectrums. This article will use the terms “male,” “female,” or both to refer to sex assigned at birth. Click here to learn more.

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Many vegetables contain phytoestrogens. Credit: Dougal Waters/Getty Images

Phytoestrogens are naturally occurring compounds found in over 300 plants. They mimic estrogen, which is a hormone that has many functions in the body.

In females, estrogen influences sexual development, menstruation, and libido. In males, adequate estrogen also supports libido and sexual function, including the ability to get an erection.

In all sexes, estrogen plays a role in regulating the metabolism of fats and glucose, bone strength, and brain health. As a result, having adequate amounts of estrogen is important.

Phytoestrogens may have a similar effect to estrogen in the body. They are also antioxidants and are anti-inflammatory.

However, most foods contain low amounts of phytoestrogens. In comparison to the amount of estrogen the body naturally produces, the intake from everyday foods is usually very small.

Phytoestrogens imitate estrogen because their chemical structure is very similar to that of estradiol. This is a form of estrogen the body produces.

When phytoestrogens enter the body, the body’s estrogen receptors treat them as if they were estrogen. But the body also does not absorb the phytoestrogens from foods very well. As a result, a person has to eat relatively high amounts of them to affect their health.

For example, soy contains a phytoestrogen known as isoflavone. A person needs to consistently consume between 40 and 70 milligrams (mg) per day, or an average of 50 mg per day, of isoflavones to produce health effects.

In Asia, where soy products are a staple food, the average daily intake of isoflavones is between 15 and 50 mg. In the West, the average amount is only around 2 mg per day.

This means most people are probably not eating enough phytoestrogens to have any effect on their health overall.

Some foods that contain phytoestrogens include:

Soy products

Unprocessed soybeans are high in the most well-studied phytoestrogen, isoflavones. Processing soybeans into different foods, such as tofu, reduces their isoflavone content.

Examples of products containing soy include:

  • tofu
  • tempeh
  • miso

Nuts and seeds

Flaxseeds are one of the main sources of a type of phytoestrogen known as lignan. To a lesser extent, many other nuts and seeds also contain phytoestrogens, including peanuts and sunflower seeds.

Grains

Some grains contain also contain lignans. These include:

  • wheat
  • rye
  • oats
  • barley

Dairy

Dairy products contain phytoestrogens, too. This includes:

  • cow’s milk
  • yogurt
  • butter

Fruits and vegetables

Certain fruits contain phytoestrogens, including:

  • apples
  • pomegranates
  • grapes
  • berries

Vegetables that contain phytoestrogens include:

  • garlic
  • turmeric
  • carrots
  • celery
  • potatoes
  • sweet potatoes
  • broccoli
  • cabbage
  • spinach
  • alfalfa sprouts
  • collard greens
  • beans

Herbs

Some plants people use as herbal medicine also contain phytoestrogens, including:

  • red clover
  • hops
  • chaste berry

Drinks

The following beverages are sources of phytoestrogens:

  • coffee
  • tea
  • beer
  • red wine

Scientists are still learning about what the benefits of phytoestrogens may be.

Additionally, a 2020 research review indicates that whether phytoestrogens are beneficial depends on the person, their hormone levels, how much they consume, and how much their body absorbs.

Phytoestrogens may:

Reduce menopause symptoms

A 2022 study evaluated the effects of giving 40 mg of soy isoflavones twice daily for 12 weeks to perimenopausal and postmenopausal women. In each group, respectively, the authors recorded the following results:

  • 42.5% and 33.1% reduction in hot flashes
  • 45% and 30.1% reduction in sleep disturbances
  • 37.5% and 40% reduction in symptoms of depression
  • 16.1% and 14.2% reduction in sexual dysfunction

The authors note that while isoflavones cannot completely replace hormone therapy, they have a “good safety profile” and may be suitable for long-term use. Twice daily doses appear to be the most effective.

Lower the risk of osteoporosis

Low estrogen can contribute to weak bones, or osteoporosis. Males and females can both experience osteoporosis, but females can get it earlier in life because of menopause.

A 2019 review of previous research notes that results on whether soy isoflavones can prevent osteoporosis are mixed. One meta-analysis found a weak association between them and an increase in bone density.

Another study found that older women who consumed soy milk for over a year had a 2.3% increase in bone density. However, more research is necessary to prove it has a significant benefit.

Reduce the risk of cancer

According to a 2020 review of previous research, there is evidence that phytoestrogens in soy reduce the risk of numerous types of cancer, including breast, ovarian, and prostate cancers.

The data so far suggests that the more soy isoflavones a person consumes, the less likely they are to get these conditions.

Improve cancer treatment

There have been some claims that phytoestrogens help with treating cancer, as well as preventing it. They may improve the outcomes for:

  • Chemotherapy: The 2020 review includes previous studies that found certain phytoestrogens may enhance chemotherapy drugs, such as cisplatin, 5-fluorouracil, and topoisomerases. However, this depends on the compound. Some phytoestrogens have shown no effect.
  • Radiation therapy: The phytoestrogen genistein may increase the sensitivity of leukemia cells to radiation, while also protecting noncancerous cells. The same may also be true for resveratrol.
  • Hormone therapy: Doctors use hormone therapy to treat tumors with hormone receptors. There is some evidence that certain phytoestrogens may enhance these treatments, but the concept is still controversial.

More research is needed to fully understand whether phytoestrogens could play a useful role in cancer treatment. Additionally, phytoestrogens may not be appropriate for all types of cancer.

Benefit skin aging

Estrogen plays a role in skin health, and its reduction in menopause may contribute to the visible signs of aging due to a loss of collagen and elasticity. In addition to changes in appearance, wounds can also heal more slowly.

A 2021 narrative review notes that topical phytoestrogens may be a promising treatment. Some early studies have shown positive results, and the authors argue that phytoestrogens may have similar effects to topical estrogen creams but without as many side effects.

However, more high quality studies are necessary to determine the effectiveness and safety of this approach.

Research indicates that most people in Western countries do not eat enough phytoestrogens for them to have any health effects. However, people may still have concerns about the impact they could have. Here is what the research says.

Thyroid function

According to a 2020 research review, some studies have found that isoflavones can contribute to an underactive thyroid in people who already have an iodine deficiency. Iodine is a nutrient that is essential for thyroid function.

However, there are few studies proving this also happens in people with adequate iodine and a healthy functioning thyroid. Those with subclinical hypothyroidism or a thyroid deficiency may need to avoid consuming large amounts.

Low testosterone

In 2018, a study on protein supplements showed that soy had no effect on testosterone levels in males. In the study, 48 college-aged men did resistance training for 12 weeks. Some took soy protein, some took whey protein, and others took a placebo.

While whey protein resulted in higher testosterone levels, soy did not decrease it. It also did not increase estrogen levels.

A 2021 review of 38 previous clinical trials showed the same conclusion. The researchers found no evidence that either soy or isoflavones affected testosterone or estrogen levels in males.

Feminizing effects in males

Some people worry that eating too much soy, or other phytoestrogen-containing foods, may have feminizing effects on the body, such as causing breast tissue growth.

There is no scientific evidence to support this in humans. Studies demonstrating this effect have used high doses of phytoestrogens in rats or other animals.

A 2021 study involving 147 infants compared the effects of soy formula to cow’s milk formula and breastfeeding. From birth to 28 weeks of age, there were no differences in testosterone levels between the groups.

The group receiving soy formula did have a more rapid growth in penis length, and a slower growth in distance between the anus and genitals, in comparison to the breastfed group. This may indicate that soy has some effect on sexual development, but the authors observed no harmful effects.

Additionally, there were no differences between soy and cow’s milk formula.

Impact on fertility

Another concern about phytoestrogens is the impact they may have on fertility in males.

However, researchers conducting a 2020 review concluded that the research to date shows no effect of phytoestrogens on semen quality or infertility risk. In fact, they noted that some studies show a beneficial effect.

For example, a 2020 study in the United Kingdom involving 1,907 males with difficulty conceiving found that the soy isoflavone daidzein appeared to be a protective factor for sperm motility.

More research is necessary to fully understand how phytoestrogens work. Unless a person is taking phytoestrogen supplements, though, it is unlikely they will be consuming a harmful amount.

Phytoestrogens are plant-based compounds with a similar chemical structure to estrogen, a hormone that is present in all humans and is important for health. The potential benefits and risks of consuming high levels of phytoestrogens are not yet fully understood.

However, most foods contain only small amounts of phytoestrogens and are unlikely to cause any health effects, positive or negative, when a person consumes them in moderation. Even at therapeutic doses, the research on any potential risks of phytoestrogens remains mixed.

For those with low estrogen, adding more sources of phytoestrogens to the diet may reduce symptoms or the risk of osteoporosis. Anyone considering taking phytoestrogen supplements should discuss it with their doctor first.