There’s a lot of conflicting information about soy milk and estrogen. The confusion is understandable because research on how soy milk affects estrogen and other hormones is still ongoing.
Understanding soy milk’s connection to estrogen will help ease your concerns.
Soy milk contains isoflavones - a type of phytoestrogen (plant estrogen). They have a similar structure to human estrogen and can weakly block or mimic estrogen activity in the body.
Human estrogen is much stronger than soy milk’s isoflavones. So soy milk can’t affect estrogen levels unless you have very potent or high levels of isoflavones and low levels of estrogen in your body.
In this article, we’re going to look at when and how soy can affect estrogen levels. We'll also explore the pros and cons of soy milk’s estrogen-like effects on the body.
When Does Soy Affect Estrogen Levels?
Soy can affect estrogen levels depending on two things:
The Type Of Soy Product
Although phytoestrogens are weaker than estrogen, they can have substantial effects if highly concentrated.
Soy milk doesn’t affect estrogen levels as much as supplements with concentrated levels of soy proteins or isoflavones.
That’s why there are more cases of adverse reactions related to soy supplements than soy milk.
Including soy milk in your diet is much safer than supplementing with high doses of soy isoflavones.
You just need to drink it in moderation to enjoy its long-term benefits.
For reference, here's a look at how isoflavones are in common soy products based the USDA database.
Food | Isoflavones |
|---|---|
Soybean Butter | 0.57 |
Soy Hot Dog | 1.00 |
Soy Sauce | 1.18 |
Soy Milk | 2.56 |
Soy Cheese (Mozzarella) | 6.02 |
Soy Burger | 6.39 |
Soy Cheese (Parmesan) | 6.40 |
Soy Cheese (Swiss) | 7.90 |
Soy Noodles | 8.50 |
Tofu (Silken) | 18.04 |
Soy Yogurt | 33.17 |
Soy Paste | 38.24 |
Soy Fiber | 44.43 |
Soybean Chips | 54.16 |
Tempeh | 60.61 |
Soy Protein Drink | 81.65 |
Soy Protein Isolate | 91.05 |
Soybeans | 154.53 |
Soy Flour | 178.10 |
A Person’s Estrogen Levels
As mentioned earlier, estrogen levels can influence how soy’s isoflavones affect your body.
For instance:
Postmenopausal women have low estrogen levels, so isoflavones might have noticeable estrogenic effects on their bodies.
On the other hand, isoflavones might affect premenopausal women differently because of their high estrogen levels.
Here are the normal levels for estradiol (the primary form of estrogen):
Normal Estrogen Levels | |
|---|---|
Premenopausal Women | 30 - 400 pg/mL |
Postmenopausal Women | 0 - 30 pg/mL |
Men | 10 - 50 pg/mL for men |
Pregnant Women (1st Trimester) | 154 - 3,243 pg/mL |
Pregnant Women (2nd Trimester) | 1,561 - 21,280 pg/mL |
Pregnant Women (3rd Trimester) | 8,525 - >30,000 pg/mL |
Boys (1-10 years old) | <5 - 20 pg> |
Girls (1-10 years old) | 6 - 27 pg/mL |
Note: Estrogen levels can fluctuate. Consult your doctor to check if your estrogen levels are in a healthy range.
Health Benefits Of Soy Milk’s Isoflavones
A soy-rich diet can have the following benefits:
Treatment Of Menopausal Symptoms
Low estrogen levels in menopausal women can cause symptoms like hot flashes, insomnia, and mood changes.
Hormone replacement therapy (HRT) was traditionally used to treat menopausal symptoms. However, there were concerns about its potential negative effects.
Those concerns lead to the use of alternative treatments using phytoestrogens.
As such, soy-rich diets and isoflavone supplements have become popular among women who want to manage their estrogen levels.
The North American Menopause Society published a study where women used soy to reduce menopausal symptoms.
Researchers found that the frequency of the hot flashes was lower by the end of the trial.
Fertility Treatments
Research shows that soy isoflavones are beneficial for women undergoing fertility treatments. Women who included soy foods in their diet had higher clinical pregnancy rates, fertilization, and live births.
A clinical study also showed that soy isoflavones benefit women with polycystic ovarian syndrome (PCOS).
PCOS is a hormonal imbalance that can cause acne, irregular periods, infertility, and unwanted hair growth.
Researchers found that soy’s phytoestrogen had protective effects on metabolic and hormonal abnormalities associated with PCOS.
Women with PCOS also develop health issues such as :
- Type 2 Diabetes
- Gestational diabetes
- Heart disease
- High blood pressure
- High LDL (“bad”) cholesterol
- Stroke
- Depression and anxiety
Soy milk is good for women with PCOS because it might help manage such symptoms.
Protection Against Hormonal Cancers
Until recently, there was a misconception that soy was a cancer risk factor. However, the American Cancer Society refuted this belief.
Updated studies show that the phytoestrogen in soy milk lowers one’s vulnerability to cancer.
The isoflavones bind to estrogen receptors and block potent estrogen hormones that could potentially cause hormonal cancer.
A controlled study published in The American Association For Cancer Research Journal found that soy isoflavones can slow down prostate cancer progression.
They can lower the risk of prostate cancer formation as well.
Research also found that isoflavones could lower cancer survivors’ risk of cancer recurrence and death.
They might counteract potent hormones, reducing the need for more estrogen production and increasing steroid production.
Isoflavones might also help fight against cancer because they are protective antioxidants. They can regulate oxidative stress and reduce damage caused by free radicals.
Bone Health
Osteoporosis is a condition that weakens bones by causing loss of bone density.
Menopausal women often suffer from this condition because they have low estrogen levels.
Estrogen is essential for bone health because it promotes the activities of cells that form new bones.
Research on soy isoflavones and osteoporosis showed a 54% increase in bone density by the end of the trial.
Thirty-six other studies also show that isoflavones can help improve bone health or prevent osteoporosis.
Drinking soy milk might help strengthen your bones because of its isoflavone, calcium, and iron content.
Prevention Of Heart Diseases
Estrogen affects heart health by influencing good and bad cholesterol levels.
Low estrogen levels lead to the increase of harmful cholesterol (LDL). High LDL levels then lead to the build-up of fat in the arteries, contributing to strokes and heart attacks.
According to The American Heart Association, postmenopausal women are increasingly using estrogen therapy to prevent heart diseases.
Studies show that soy phytoestrogen can also lower harmful cholesterol. Therefore, a soy-rich diet might be an excellent alternative to estrogen therapy.
Regular servings of soy milk might do wonders for your heart health.
Low Blood Pressure
Blood pressure experts claim that estrogen keeps blood pressure down. It does so by widening blood vessels allowing blood to flow easily.
People with low levels of estrogen are vulnerable to hypertension. Fortunately, soy isoflavones can help them lower blood pressure.
A clinical trial found that soy milk can help people with mild to moderate hypertension manage their blood pressure levels.
Skin Health
Estrogen is essential for skin health.
It’s responsible for the skin’s hydration, thickness, and elasticity. Estrogen also influences the production of hyaluronic acid, making your skin look younger.
Low estrogen levels lead to wrinkling, dryness, thin skin, less collagen, and decreased elasticity.
You can manage your skin health by including soy milk in your diet.
Research shows that phytoestrogen can act through estrogen receptors to offer the same benefits as human estrogen.
Soy isoflavones can also influence protein, collagen, and hyaluronic acid production. They can also protect your skin from oxidative stress, and harmful UV rays, among other things.
Risks Associated With Soy Milk’s Isoflavones
Thyroid Health
Estrogen affects thyroid function because it stimulates the growth of the thyroid gland. Too much estrogen can enlarge the thyroid gland, cause goiter, or block the absorption of thyroid hormones.
Excess soy intake might similarly interfere with thyroid function, depending on your estrogen levels and thyroid health.
You can safely consume soy milk if you have enough iodine, sufficient estrogen levels, and normal thyroid function.
However, soy milk is risky for people with low estrogen levels or hypothyroidism. Soy isoflavones might also interfere with the absorption of thyroid medication.
There’s still ongoing research on isoflavones and thyroid health. But it’s best to consult your endocrinologist before including any soy product in your diet.
Rare Hormonal Changes In Men
There’s only one rare case on record where soy phytoestrogens caused hormonal changes in a man.
The case study involved a 60-year-old man with very high estrogen levels and increased breast tenderness. He drank 12 cups of soy milk daily, which is more than the recommended amount.
Babies who consume soy-based formula also have high estrogen levels because of their diet. There were concerns that large concentrations of isoflavones in the formula would have negative reproductive effects on male infants as they grew older.
However, reports showed they had no reproductive issues as adolescents and young adults.
Moderate consumption of soy milk won’t extreme hormonal changes in men. The American Institute For Cancer Research even claims drinking 1 to 2 cups of soy milk daily is safe for both men and women.
Allergies
Estrogen causes an increase in histamine - a hormone that triggers allergic reactions.
Research shows that women’s allergic reactions peak when their estrogen levels are at their highest. This could be under oral contraceptives, around menstruation, during pregnancy, and when undergoing hormone replacement therapy.
High levels of soy phytoestrogens might trigger similar allergic reactions, especially during such times when women are most sensitive.
Also, avoid soy milk if you have soy allergies. And consult your doctor if you’ve never had soy foods and want to consume them for the first time.
The Soy Milk - Estrogen Connection
Soy milk doesn’t contain estrogen but has phytoestrogens such as isoflavones.
Isoflavones are too weak to affect you unless they’re highly concentrated in your body and you have low estrogen levels.
Studies show that isoflavones have many health benefits.
They can positively influence your reproductive, heart, bone, and skin health. Soy isoflavones might also help you treat and prevent hormonal cancers, among other health conditions.
Although isoflavone supplements are tempting, we recommend that you add more soy foods to your diet instead. Some isoflavone supplements are too potent and can cause different or negative effects on your body.
Consuming too much soy milk or soy foods can also lead to thyroid issues, allergic reactions, and severe hormonal changes in some cases.
We advise that you enjoy soy milk in moderation to avoid putting your health at risk.
Remember to consult your doctor if you want to include soy milk in your diet, especially if you have health issues or are under medication.
