Phytoestrogens are substances found in plants that mimic the effects of estrogen hormones in the human body. Studies have shown they have both positive and negative effects. Because they cause hormonal disturbances, they can be especially dangerous during pregnancy and early childhood.
A handful of studies has shown that phytoestrogen supplementation improves the hormonal profile of PCOS patients. While this would suggest they are also helpful in hormonal-type acne, we have to take these results with a grain of salt. As far as hormonal balance is concerned, phytoestrogens are a double-edged sword.
Phytoestrogens bind to estrogen receptors, but they are orders of magnitude weaker than real estrogens. In other words, they can fool the body into thinking estrogen levels are sufficiently high without actually providing the same effect real estrogens have.
In some cases they even worsen the hormonal imbalance. The human body uses an enzyme called aromatase to convert androgens into estrogens. Phytoestrogens can block that conversion. This leads to a situation where you have too much androgens and too little estrogens – the very imbalance that causes hormonal-type acne.
Finally, phytoestrogens can competitively inhibit the production of estradiol by aromatase, which would lead to lower endogenous estrogen levels.
Jefferson, W. N., Patisaul, H. B. & Williams, C. J. Reproductive consequences of developmental phytoestrogen exposure. Reproduction 143, 247–60 (2012). https://www.reproduction-online.org/content/143/3/247.full
Several studies have confirmed that phytoestrogen-rich diets can reduce estrogen levels in women. Many studies showed 20 to 30% reduction in estradiol levels after just one month of soy-rich diet.
Unfortunately, there’s very little research on how estrogens affect acne. The research we have suggests estrogens balance the effect of androgens and could protect against acne.
As such, it’s probably a good idea for women suffering from hormonal-type acne to avoid phytoestrogen-rich foods. Or at least treat them as suspect foods and keep an eye on how they affect your skin and menstrual cycle.
In 2009 Canadian researchers measured the phytoestrogen content for 121 common foods available in local supermarkets. Their results show that by far the biggest sources of phytoestrogens are:
- Soybeans (103920 micrograms/g)
- Flax seeds (379380 micrograms/g)
- Sesame seeds (8000 micrograms/g)
- Chia seed (similar quantity as sesame seeds, source)
These four foods have orders of magnitude more phytoestrogens than other foods. Just avoiding those foods cuts your phytoestrogen exposure by at least 90%.
You can find more detailed data on phytoestrogen content in common foods here: https://www.dietaryfiberfood.com/phytoestrogen-hormones/phytoestrogen-food-sources.php. But for practical purposes avoiding anything made of the above three foods should be sufficient.