Soy Isoflavones Side Effects

Updated April 17, 2017

Soy isoflavones are oestrogen-like compounds called phytoestrogens found in soy. They can be taken as supplements or from eating soy food products. The American Hearts Association recommends adults add 25g of soy into their daily diet due to its many health benefits, such as preventing hormone-related cancers, reducing heart disease risks and a plant-based substitute for protein. However, many side effects are associated with soy isoflavones.

High Blood Pressure

A 2004 case study by the Department of Nutrition of Arizona University on soy isoflavones hormone replacement therapy for post-menopausal women revealed elevated blood pressure to the point of hypertensive crisis.


Since soy is a type of bean, it produces intestinal effects like gas, constipation, diarrhoea and bloating.


The oestrogen-like hormones may induce ovulation and affect fertility in women.

Birth Defects

Pregnant women should not consume a high level of soy isoflavones due to increased risks of low bone density for the baby and possible birth defects for male babies, such as hypospadias in which the urinary opening is abnormally placed.


Some may experience unexpected allergic reactions such as difficulties in breathing and skin rash.

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About the Author

LH Lee spent two years backpacking from 2007 to 2009. Since her return in 2009, she has contributed various travel articles to Off Track Planet and Matador. Lee holds a Bachelor of Fine Arts in screenwriting from the School of Visual Arts and is a recipient of The Media Workshop from UCLA.