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What are isoflavones? 

Isoflavones are naturally occurring plant compounds that have similar structural properties to estrogen. They are also known as phytoestrogens. Isoflavones are found in soybeans as well as other legumes, nuts, fruits, and cereals. 

What are sources of isoflavones? 

Isoflavones are a type of flavonoid found in food. There are two main types of isoflavones: genistein and daidzein. The main source of isoflavones are soybeans and soy foods such as soy nuts, soy milk, tofu, miso, and edamame. 

Does soybean oil contain isoflavones? 

Although soybeans are a major source of isoflavones, the content of isoflavones in soybean products varies greatly with processing. Soybean oil is highly refined, meaning it goes through several processing steps to produce it. Therefore, soybean oil has insignificant levels of isoflavones and is not considered a good source of these types of flavonoids. 

What are the health effects of isoflavones? 

Isoflavones have exhibited antioxidant, anti-inflammatory, antimicrobial, and anticancer properties. Isoflavones help reduce oxidative stress in the body by neutralizing free radicals. Because of this, they are particularly helpful in chronic diseases in which inflammation occurs such as obesity, atherosclerosis, rheumatoid arthritis, and cancer. Isoflavones are also beneficial for perimenopausal and postmenopausal women becuase they help alleviate some of the side effects of diminished natural estrogen in the body. 

What do isoflavones do for fertility? 

Isoflavones are phytoestrogens, meaning they are structurally similar to estrogen. Phytoestrogens have a phenol ring similar to estrogen that can bind to specific estrogen receptors in certain tissues of the body. Studies have shown that consuming soy products in typical doses poses no harmful effects on ovulation in women or fertility in men. Even in amounts greatly exceeding the typical soy intake, soy consumption does not lower testosterone in men, raise estrogen levels, or adversely affect sperm. There is some research showing that extremely high soy intake (>60g soy protein daily) can increase menstrual cycle length and decrease FSH and luteinizing hormone levels. However, most people do not consume this much soy protein per day and therefore should not be a great concern for those trying to conceive. 

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Photo of Kristin Ricklefs-Johnson

Medically reviewed by:

Kristin Ricklefs-Johnson, Ph.D., RD

Kristin is an RDN who also earned her Ph.D. in Nutrition from Arizona State University with an emphasis on insulin resistance, lipid metabolism disorders, and obesity. She completed her post-doctoral fellowship at Mayo Clinic where she focused on nutrition-related proteomic and metabolic research. Her interests include understanding the exact mechanism of action of various genetic variations underlying individual predispositions to nutrition-related health outcomes. Her goal is to help all individuals prevent chronic diseases and achieve long, healthy lives through eating well.

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