Soy protein-containing foods like tofu, textured vegetable protein and edamame do not significantly increase estrogen levels.
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Soy is a top source of protein and a useful and versatile component of a healthy plant-based diet. However, reports about the effects of soy on hormones make some people wary about eating it. Fortunately, based on up-to-date research, most experts agree that soy is safe.
Soy protein-containing foods, like tofu, textured vegetable protein and edamame, do not significantly increase estrogen levels in people of any sex. Soy may have mild, beneficial anti-estrogenic or estrogenic effects, depending on your time of life.
As explained by the Centers for Disease Control and Prevention (CDC), soy-based foods are the biggest dietary suppliers of isoflavones, which when consumed and metabolized have the potential to act as phytoestrogens, a class of compounds with weak estrogenic effects.
The CDC says soy estrogens, such as edamame or tofu estrogens, are much less potent than the hormone produced by the human body, but depending on your diet can be present in much greater quantities in the blood.
For example, infants who consume soy-based formula can have blood concentrations of isoflavones that are 13,000 to 22,000 times higher than the natural level of estrogen in babies not fed infant formula. This might seem like a worry, but followed through to adolescence and young adulthood, soy-fed babies show no adverse reproductive effects.
Neither does consuming soy, estrogens appear to have a negative effect in people assigned male at birth (AMAB). An August 2018 study in Scientific Reports found that when men (the language used in the study) combined soy protein supplementation with resistance exercise training, there were no changes to their levels of sex hormones.
Read more: Is Eating Soy Actually Bad for Your Health?
According to Harvard Health Publishing, the effects of soy on hormones in people assigned female at birth (AFAB) can be to either increase or decrease the effects of estrogen, which may benefit both those who are younger and older.
People who have not gone through menopause have much higher circulating levels of estradiol — the main type of estrogen hormone — than those who have gone through menopause, and in this younger age group soy isoflavones may compete with the actual hormone for receptor sites in the body, damping down the effect of excess estrogen. As too much estrogen can be linked with abdominal weight gain, fibroids, fatigue and anxiety, this may be beneficial for people who have not gone through menopause.
Around menopause, when estrogen levels dramatically fall, isoflavones can switch roles and are thought to help modestly supplement low levels of estrogen, which might have benefits for this group. Results are mixed, but a December 2014 review in the journal Climacteric found that plant estrogens, including soy estrogen, helped reduce the frequency of hot flashes in those going through menopause, without harmful side-effects.
Read more: 13 Surprising Vegetarian Sources of Protein
Soy Estrogen and Breast Cancer
The big question for most people wondering whether soy is safe is whether or not it can contribute to breast cancer.
In fact, far from being a breast cancer risk, the Mayo Clinic says that soy is one of the foods that can reduce breast cancer risk. Those who eat plenty of soy products from an early age reduce their risk of breast cancer in later life. This protective effect is less dramatic for people AFAB who eat smaller amounts of soy or who start eating soy later in life.
Even if you are a breast cancer survivor, it's OK to carry on eating soy products and to do so may be beneficial. A June 2017 study in Cancer surveyed more than 6,200 American and Canadian women (the language used in the study) with breast cancer and found those who ate the highest amounts of isoflavones had a lower risk of dying from any cause.
Expert advice from the American Cancer Society is that soy foods are healthy and safe. But soy supplements contain much higher isoflavone concentrations than food and aren't recommended until more research is carried out on them.
FAQs
Premenopausal women have much higher circulating levels of estradiol—the major form of estrogen in the human body—than postmenopausal women. In this context soy may act like an anti-estrogen, but among postmenopausal women soy may act more like an estrogen.
Does soy have estrogen side effects? ›
Soy contains isoflavones which are changed in the body to phytoestrogens. Phytoestrogen molecules are similar in chemical structure to the hormone estrogen. In some cases, these phytoestrogens can mimic the effects of estrogen. In other cases, these phytoestrogens can block the effects of estrogen.
Does soy increase estrogen pubmed? ›
The studies in women have provided modest support for beneficial effects. One cross-sectional study showed serum estrogens to be inversely associated with soy intake.
Is soy really feminizing? ›
These claims exist despite definitive data showing neither soy nor soy isoflavones lower testosterone levels,1 raise estrogen levels,1 affect sperm or sem*n,2-4 or cause gynecomastia in men. So, there may be some value in outlining the origins of this feminizing myth.
Should men avoid soy? ›
Yes, Boys Can Enjoy Soy!
The U.S. departments of Agriculture and Health and Human Services agree adding tofu, tempeh and soy protein powders to the protein category of their 2020-2025 Dietary Guidelines for Americans.
What are the negative effects of soy? ›
The most common side effects of soy are digestive upsets, such as constipation and diarrhea. Soy may alter thyroid function in people who are deficient in iodine. Current evidence indicates that it's safe for women who have had breast cancer or who are at risk for breast cancer to eat soy foods.
How much soy is too much for a woman? ›
How much soy is recommended? Can too much soy be harmful? Numerous clinical studies have found that daily consumption of up to 50 grams of soy protein is not only safe, but may also be effective in improving risk factors for chronic disease such as some types of cancer, diabetes, and cardiovascular disease.
What are 5 estrogen foods to avoid? ›
For example, many studies have found that Western-type dietary patterns characterized by high intakes of red meat, processed foods, sweets, dairy, and refined grains are consistently associated with higher estrogen levels ( 3 , 15 , 16 , 17 ).
Are eggs high in estrogen? ›
Another source of estrogen in foods is animal estrogen. Products like eggs or milk contain high estrogen levels because they are produced in parts of the animal's body that regulate its hormones. Eating high estrogen foods can help people who suffer from various conditions related to low estrogen levels.
What drink increases estrogen? ›
Red wine may contain higher levels of phytoestrogens due to its fermentation process. Beer also contains phytoestrogens, and its effect can be seen even with moderate intake. Hard liquor is metabolized faster than beer or wine, so it may have a more immediate effect on estrogen levels.
Not enough evidence exists to suggest a link between soy consumption and hormone changes in the body such as increased serum estrogen, breast cancer risk, thyroid hormone imbalances, and infertility.
Does soy protein increase estrogen in men? ›
When observing the effect of isoflavones/phytoestrogens on testosterone levels in men, extensive studies show that they have no effect on testosterone or estrogen in men. Furthermore, both men in the case studies discussed they derived a majority of their calories from one food – soy.
Does soy increase breast size? ›
Therefore, many people, especially women, believe that soybean-derived food can help their breasts grow bigger. This is in fact not correct. There is no evidence showing that phytoestrogen can make your breasts bigger, as the level of isoflavone found in soybeans is not high, and thus, not largely effective.
Does protein increase estrogen? ›
Adequate protein intake is essential for the production of estrogen, progesterone, and testosterone. All of these are critical for reproductive health, bone density, mood regulation, and more. One way that protein supports healthy hormones is by helping to balance blood sugar levels.
Does plant protein raise estrogen? ›
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.
Is soy a hormone disruptor? ›
Because it is a hormonally active diet, however, soya can also be endocrine disrupting, suggesting that intake has the potential to cause adverse health effects in certain circ*mstances, particularly when exposure occurs during development.
