Where Do Isoflavones Come From?

Soybeans are the best source of isoflavones

Most people get the main portion of their isoflavones from soy, and that is where they are found in the most abundance.

But you can also find them in red clover, kudzu, mung beans, alfalfa sprouts, black cohosh, chickpeas, and other plant foods. So how do you know which isoflavone source is best for easing the transition through menopause?

Simple. Of all isoflavone sources, soybeans have the highest content of genistein, the isoflavone that has the greatest ability to reduce the frequency and severity of hot flashes.

Isoflavone Contents of Some Foods (mg/kg as is)
Food Item Genistein Daidzein
Soybeans (dry) 738 466
Clover sprouts 4 ND*
Green beans (fresh) ND ND
Lima beans (dry) 0.1 0.2
Garbonzo beans (dry) 0.6 0.4
Pinto beans (dry) 2.6 0.1
Alfalfa sprouts ND ND
Lentils ND ND

*ND=not detectable

Source: USDA, Iowa State University Database on the Isoflavone Content of Foods, Release 1.2 -- 2000

While there are many clinical studies on soy isoflavones and various human health conditions, there are relatively few clinical studies on red clover or kudzu and those same human health conditions. Studies on red clover have been mixed.

The predominant isoflavone forms in red clover are biochanin-A and formononetin. In kudzu, the predominant isoflavone forms are daidzein and puerarin.

Soy isoflavones like Novasoy®, which are made from virtually the whole soybean, have higher genistein contents, just like the soybean itself. Genistein makes up approximately 50% of the isoflavones in soy, compared to less than 1% genistein in red clover and just 6% genistein in kudzu, for example.

That makes soy isoflavones like Novasoy the obvious choice for relief from menopause symptoms.