We haven’t come across any evidence that eating soybeans (or soya beans) can help acne. What you might have heard about is the report of a very small study, suggesting that a moisturiser containing soya can help acne: it reduced the number of inflamed spots and general redness, and was thought to be starting to reduce the numbers of comedones.
The study lasted only 35 days, so the researchers could not be sure of its long-term effects; a bigger and longer-lasting study is needed to look at this further. Soya contains what are called phyto-oestrogens. These are plant versions of the female hormone oestrogens, so the moisturiser might work by altering the effect of androgens on the skin and thus reducing the production of sebum.
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