Soy Milk and Estrogen Levels: An Explanatory Guide


August 16, 2022

If you enjoy tofu or choose soy milk over dairy, you may be curious about how soy affects your health. However, there seem to be more doubts than answers regarding the role of soy plays in women’s bodies, especially concerning menopause and breast cancer. There are also many misconceptions.

Rumours about soy milk and estrogen may result in you questioning the security of this beverage. But do not worry; you do not have to miss your favourite soy latte. While soy milk includes compounds structurally related to estrogen, they do not operate like this hormone.

For many people, soy milk can be a portion of a nutritious, balanced diet and may undoubtedly have a few beneficial effects. Part of the uncertainty is due to the difficulty of soy’s consequences on the body. 

Soy: An Introduction

The soy in the food supply is a refined commodity of the soybean, and tofu is one of the most widespread sources. You will increasingly discover it in dairy substitutes like soy cheese, soy milk, and foods made for vegetarians, like soy burgers and other meat alternatives.

A study indicates that soy includes phytoestrogens or plant-based estrogens. These are the primary two isoflavones— daidzein and genistein, that function like estrogen, the female sex hormone within the body. Because estrogen plays a role in everything from breast cancer to sexual reproduction, this is where a maximum of the soy discussion arises.

Soy is unusual in that it includes a high concentration of isoflavones, a kind of plant estrogen (phytoestrogen) identical to human estrogen but with many fewer effects.

Soy isoflavones can compel estrogen receptors in the body and cause vulnerable estrogenic or anti-estrogenic action. Furthermore, soy isoflavones and soy protein occur to have various activities in the body based on the additional factors:

Type of Soy

  • Whole soy diets such as tofu and soybeans
  • Processed like soy-based veggie burgers or soy protein powders
  • Fermented or unfermented soy foods
  • When using supplements, contain isoflavones or soy protein.

Does Soy Milk Contain Estrogen?

A study indicates that soy milk does not include estrogen but contains phytoestrogens. These are primarily present in the three forms of isoflavones: Daidzein, Genistein, and Glycitein.

Research indicates that the number of isoflavones in soy milk (and additional soy products) is affected due to the agricultural situations, the soybean cultivar, and processing. However, the specific concentrations of isoflavones in your cup of soy milk, i.e. phytoestrogens, are not similar to estrogen.

The HealthifyMe Note

Depending on the level of hormones already present in the body, soy may have estrogenic effects. Estradiol, the main form of oestrogen in the human body, circulates in the blood at substantially higher levels in premenopausal women than in postmenopausal women. Soy may behave as an anti-estrogen in this situation, but it may act like oestrogen in postmenopausal women. Breast cancer in women is divided into hormone-positive and hormone-negative subtypes, and these tumours respond differently to estrogens.

Estrogens vs Phytoestrogens 

Estrogens are a group of steroid hormones, usually categorised as female sex hormones. The three significant estrogens secreted in the female body are Estrone (E1), Estradiol (E2), and Estriol (E3). The most well-known is estradiol, also known scientifically as 17β-estradiol.

Phytoestrogens are the isoflavone compounds in soy and nonsteroidal plant hormones structurally related to estrogen. They can compel the two kinds of estrogen receptors in the body, realised as ERα and ERβ,3 and commonly choose the latter of those two receptors.

According to research, your body may react similarly to or differently when phytoestrogens attach to these receptors than when oestrogen does. For example, when estradiol attaches to the ERβ receptor, it is thought to facilitate the growth of specific cancer cells. Yet when particular isoflavones bind to the receptor, it is assumed that they may deter the development of those cancer cells.

Most studies associating soy consumption with an increased risk for breast cancer and other types of cancer are conducted on lab animals. However, the American Cancer Society (ACS) notes that because humans metabolise soy more than rats, these conclusions may not apply to people. Furthermore, studies examining how soy affects humans have shown no evidence of a possible threat.

The ACS asserts that because research on the connection between soy and cancer is still developing, much more examination is needed. However, as it sits, soy does not occur to present any cancer risk.

Some research indicates that soy reduces cancer risk. Early research shows that hormone fluctuations in men who eat soy products daily could protect against prostate cancer. A 2019 research found that soy intake could reduce breast cancer risk in Chinese women. However, there isn’t significant evidence that soy definitively boosts or reduces cancer risk.

Cautions with Soy

Many researchers have examined the consequence that soy may have on thyroid health. Currently, soy does not conclusively cause thyroid infection. However, restricting soy consumption may be advantageous for those on thyroid medications for hypothyroidism because soy may impair the effectiveness of some drugs. Also, avoid soy at least four hours after seizing your prescription is approved.

Possible Benefits of Soy 

Women go through menopause when their oestrogen levels fall. Soy isoflavones can sometimes lessen the symptoms of menopause since they have an estrogen-like effect on the body. However, a study claims that this effect is rather debatable.

Early information showed that soy could even lessen the risk of heart disease. While those claims were relatively exaggerated, a study does show that a diet that swaps soy for animal protein can reduce LDL or “bad” cholesterol.

Finally, research revealed that soy could help minimise bone loss correlated with osteoporosis, lessening the risk for fractures. Researchers infer their outcomes indicate that postmenopausal women and others with low bone density could profit from eating soy.

Soy Phytoestrogens and Body Estrogen Levels 

Most research shows moderate soy consumption, including soy milk, does not affect oestrogen levels. A comprehensive meta-analysis has demonstrated that this is accurate for premenopausal women. In a related investigation, postmenopausal women showed no statistically significant changes.

A tiny non-significant boost in estradiol among postmenopausal women may arouse suspicion. However, experts said that the lack of other hormonal changes “argues against a physiologically relevant estrogenic impact.”

Phytoestrogens and Cancer Risk 

Much of the discussion surrounding soy milk and estrogen arose from the early interest that phytoestrogens would simulate estrogen and boost the hazard of hormone-dependent cancers. However, the study indicates that certain breast cancers, for example, are correlated with elevated estrogen levels.

Although there is no evidence linking soy milk’s phytoestrogens to an increased risk of breast cancer. Those isoflavones can compel the estrogen receptors, potentially obstructing the activity of the more potent estrogen hormone. According to the study, this may reduce the danger of breast cancer and other cancers.

Rather than taking isoflavone supplements, stick to eating foods that contain soy. Your body may experience several side effects from using isoflavone supplements at high doses. 

Other Concerns About Soy Milk 

Two other problems related to soy milk and phytoestrogens are worth examining.

Soy Milk and Thyroid Health 

Disagreement exists over soy’s consequence on thyroid health. The excellent recommendation likely relies on your recent thyroid health:

Some specialists advise reducing soy consumption if you have mild hypothyroidism. There are concerns that soy might affect the thyroid in a way that would cause someone to cross the line into full hypothyroidism. Despite the lack of evidence, some doctors or dietitians might still utilise it.

If you retain hypothyroidism and are dealing with synthetic thyroid hormone, you should prevent drinking soy milk or consuming other soy food commodities within four hours of taking your drug.

Moderate soy use is safe if you obtain enough iodine daily and have natural thyroid function.

Soy Formula and Babies

Specialists have raised interest in the potential hormonal consequences of phytoestrogens in soy protein procedures. According to estimates, 20 to 25% of formula-fed babies receive a soy-based baby procedure. People often use these formulas as alternatives to cow’s milk-based formulas.

Infants absorb the phytoestrogens in soy products, which may result in elevated levels in their relatively small bodies. However, problems exist over whether this may influence reproductive improvement during this critical time due to their capacity to bind to estrogen receptors.

Some research has implied that soy formula during infancy is directed to heavier or longer-duration menstrual bleeding during new adulthood in females. On the other hand, early disclosure of soy protein may lead to some beneficial protective effects against hormone-dependent cancers.

However, further long-term research in this region is essential as “no compelling evidence from animal, adult human, or infant communities that dietary soy isoflavones may adversely influence human health, reproduction, or endocrine function.” It’s vital to remember that only soy formulas—not soy milk products available in stores—should be utilised as choices for feeding babies.

Benefits of Soy Milk

Despite the disagreements described above, for most people, consuming soy milk in moderation can be a healthy addition or alteration to the diet. Consider these extra benefits:

High Protein Content

Research indicates that it has the most related nutritional contour to cow’s milk compared to other milk options. For example, a cup includes a comparable quantity of calories and seven to eight grams of protein (a nutrient that considerably other milk options, like almond milk or rice milk, are lacking). 

Helps PCOS

Some study suggests soy foods may be helpful for people with polycystic ovarian syndrome (PCOS).

Improves Cholesterol

Research indicates that soy protein reduces LDL cholesterol. Though the quantity is modest, experts understand it is in the range of a 3-5% reduction when eating 25 grams of soy protein daily. You can discover this protein in foods like tofu, soy milk, and edamame.

Reduces Menopausal Symptoms

Research showed that soy protein might lessen the harshness and regularity of hot flashes during menopause.

The HealthifyMe Note

Soy is a nutrient-dense protein source that you may consume several times per week. Researchers regard soy as a health nutrient, with evidence of preventing osteoporosis, reducing hot flashes, and protecting against hormonal cancers such as prostate and breast cancer.


Soy is widely researched for its estrogenic and anti-estrogenic consequences on the body. Researchers may seem to draw contradictory results on soy, primarily because soy is examined in distinctive ways. However, results of recent population research suggest that soy has either a helpful or neutral consequence on several health conditions.

When used as an alternative to red and processed meat, soy is a nutrient-dense source of protein and is consumed several times per week. Soy is seen as a health nutrient by researchers, with indications of averting osteoporosis, taming hot flashes, and protecting against hormonal cancers like prostate and breast.

However, despite the lack of evidence, some people avoid soy because they believe it could cause thyroid issues, breast cancer, and dementia.

Research on the possible health benefits and hazards of soy is ongoing. As it proceeds, we will develop what we know about plant-based nutrition. But, for now, it looks like soy’s advantages surpass the cons.

Frequently Asked Questions(FAQs)

Q. Can drinking soy milk increase oestrogen?

A. Several studies indicate soy’s influential role in menopause. In a survey of forty-seven studies (11 of pre, 35 posts and 1 of perimenopausal women), soy isoflavone supplements put up estradiol (estrogen) degrees in postmenopausal women by 14%. Preliminary information indicates that soy product consumption, including isoflavones (phytoestrogens), can decrease serum estrogen levels. 

Q. Does soy milk increase or decrease estrogen?

A. Preliminary information suggests that consumption of soy commodities, which include isoflavones (phytoestrogens), can lessen serum estrogen levels. For example, sipping just two cups of soy milk or consuming one cup of tofu generates blood levels of isoflavones that can be five hundred to a thousand times higher than normal estrogen levels in women. 

Q. Does soy milk affect female hormones?

A. Isoflavones are a subtype of phytoestrogens present naturally in soy and function in the body as a weak oestrogen. Estrogen levels reduce during menopause, directing to indications like hot flashes. Since soy acts as a normal estrogen, it may help lessen these indications. Researches suggest soy’s helpful role in menopause. 

Q. Does soy milk have more estrogen than regular milk?

A. One of the most widespread myths regarding soy milk is that it negatively affects hormones due to toxic estrogen. Many researchers state that this is an ultimate myth. Soy contains zero oestrogens and mammalian oestrogen. 

Q. What does soy milk do to the female body?

A. Soy milk includes isoflavones, a class of chemicals known as “phytoestrogens.” These isoflavones react in the body like a vulnerable form of estrogen. Because of that, researchers have indicated that consuming soy milk and additional soy products might lessen the indications of menopause, such as hot flashes.

Q. What milk has the most estrogen?

A. In a small study suggested that after consuming cow’s milk, men’s levels of both male and female sex hormones significantly decreased. Oestrogen levels were noticeably higher in all participants—men, women, and children.

Q. What are the adverse effects of soy milk?

A. Soy can result in some mild stomach and intestinal side effects such as nausea, constipation, and bloating. It can also result in allergic reactions implicating itching, rash, and breathing difficulties in some people. 

Q. Why is Soy not suitable for females?

A. Soy, it turned out, includes estrogen-like solvents called isoflavones. And some outcomes indicated that these compounds could facilitate the growth of some cancer cells, mess with thyroid functioning, and impair female fertility. 

Q. Does soy sauce increase estrogen?

A. Phytoestrogens, typically known as isoflavones, are present in soy and can mimic the effects of the hormone oestrogen in the body. The consequences of soy isoflavones on human estrogen degrees are complicated. However, soy is safe for everyone to eat in moderation and can retain a modest impact on estrogen levels. 

Q. Can a woman drink soy milk every day?

A. According to the Dietary Guidelines for Americans, one to three eight-ounce servings of soy milk daily is safe for consumption and gives many nutrients similar to cow’s milk. Avoid soy milk blends with added sugar, and limit your intake to one serving daily.

About the Author

Nahida is a registered dietician with 9 years of experience, working extensively with individuals dealing with obesity, diabetes, thyroid and PCOD. In addition, she has worked with NGOs supporting cancer patients by providing them with nutritional counseling. After completing her post-graduation in Dietetics & Applied Nutrition from Mumbai University, she went on to finish her MBA in Healthcare Services. Nahida is also a certified diabetes educator from International Diabetes Center. Currently a Sr. Nutritionist with HealthifyMe, Nahida is looking forward to let people take their weight off their mind and body by enjoying the journey.

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