Food and drink

Does soy increase oestrogen in men?

Written by AI from saved sources. A script checks every quote and every figure against the saved sources, and a second AI compares each claim with its source. How we work and corrections

The broad 2021 review does not support a general rise in men’s blood oestrogen from soy. Soy contains plant compounds called isoflavones that can act on oestrogen receptors. A newer analysis suggests a rise in oestrogen.

Why people believe it

Germany’s nutrition information centre, BZfE, links the concern to isoflavones’ resemblance to oestrogen. It also points to their ability to mimic or block hormone action. That makes the question reasonable. One case report also describes symptoms after high soy-milk intake, including breast enlargement. These deserve attention.

“It raises my oestrogen”

The 2021 review combined 41 studies. These included controlled trials and studies without a comparison group. Data from studies without a comparison group were analysed separately from comparisons between treatment and control groups. Oestradiol was measured in 1,000 men. Oestrone was measured in 239 men. Neither showed a statistically significant change. It does not prove an effect impossible.

The 2025 analysis used a model to estimate a nonlinear rise in oestradiol. The estimated rise was about 6.5 picograms per millilitre at 72.2 mg of isoflavones daily. The comparison was with a zero mg/day reference dose. This is a statistical estimate, not a personal intake threshold. Only its abstract was saved. The authors caution that the few studies may limit how widely the findings apply. The 2021 review also discloses soy-industry relationships.

“It lowers testosterone”

The 2021 review’s pooled results found no significant testosterone change. But a separate trial studied middle-aged to older men at risk of prostate cancer returning after prostate removal. It found lower total testosterone after 18 months of soy protein isolate compared with a casein-based placebo. In that same comparison, soy protein did not affect oestradiol. Nor did it affect free testosterone. This finding concerns that patient group. Only the abstract was saved.

“It harms fertility”

An observational study involved 99 men at an infertility clinic. Sperm concentration was lower in the highest soy-food intake category than in men who ate no soy foods. The study could not establish cause. Its simple comparisons found no link with total sperm count. A separate study followed 184 men whose partners underwent IVF, a fertility treatment. It found no link between the men’s soy intake and live birth or other measured treatment outcomes. Its authors caution against extending this to conception without treatment.

“Soy milk can cause symptoms”

One case report describes low testosterone in a man. He drank about 1.2 litres of soy milk daily for three years. His product’s label suggested about 310 mg of isoflavones daily. Hormone tests improved after he stopped both soy milk and carbohydrate restriction. The authors considered weight loss an unlikely explanation. The reason: his weight when admitted in August was comparable to his weight at his first visit in May. Erectile dysfunction did not fully resolve. Oestradiol measured after stopping was low. One case cannot tell us how often this happens.

What official bodies say

EFSA’s assessment of isoflavone supplements for women around and after menopause excluded men. It was published on 21 October 2015. On 23 September 2025, the European Commission said those conclusions applied only to that subgroup of supplement users. It also said EFSA had issued no new conclusions following ANSES’s recommendations.

Germany’s BfR said on 2 August 2023 that necessary long-term safety studies of isoflavone supplements were unavailable. France’s ANSES recommended avoiding soy foods in meals served by institutions on 24 March 2025. ANSES based its general-population reference value on a higher rate of mammary-gland hyperplasia in male rats. It had moderate confidence in this value.

The Swiss FSVO’s undated FAQ was saved on 26 October 2026. It says adults may eat soy several times a week within a balanced, varied diet. It also notes uncertainty about high isoflavone intakes. At high isoflavone intakes, it urges particular caution for children, pregnant women and people with hormone-dependent diseases.

What people also ask

Does soy milk increase estrogen in males?
The broad hormone review did not find a significant increase from soy or isoflavones. The newer analysis prevents an absolute “never”.

What does soy milk do for men?
For the hormone question, studies disagree. The high-intake case report cannot predict everyone’s response.

Can soy milk cause high estrogen?
The newer analysis suggests an oestradiol increase. But it does not establish a personal threshold for high oestrogen. ANSES reports that isoflavone content varies between soy foods. It varies even among soy desserts on the French market.

Do soy milks increase testosterone?
The broad review found no significant testosterone increase from soy or isoflavones.

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