What are phytoestrogens?

Phytoestrogens are estrogen hormone-like chemicals found in plants. They include a group of chemicals such as isoflavones, flavones, coumestans and lignans. What makes this group of estrogen-like chemicals of medical interest is that their chemical structure is similar to that of estrogen in human body. And when consumed, depending on the concentration of the phytoestrogens in the diet and concentration of sex hormones in the body, life stage and gender, they have estrogenic and anti-estrogenic effects.

What are the benefits of phytoestrogens?

Several studies show that phytoestrogens have potential health benefits such as reducing risks of incidences of breast cancer, prostate cancer and cardiovascular disease. Phytoestrogens may reduce osteoporosis (bone loss) and menopausal symptoms. Besides, both flavonoid and lignan phytoestrogens have antioxidant activity. Phytoestrogen formulations are used by women in menopause as alternatives or complementary options to hormonal replacement therapy (HRT) because of concerns of side-effects or other considerations. Some studies also report potential benefits of phytoestrogens in lowering serum cholesterol levels.

What foods contain dietary estrogen (phytoestrogen)?

Estrogen is available in medically formulated pills. However, dietary estrogen (phyto estrogen) can also be found naturally in wide variety of plant-based foods, with the level varying depending on the source. The main food sources of phytoestrogen are soybean and flaxseed, and their derivatives. Other food types such as nuts, oil seeds and herbs are also good sources phytoestrogens, eventhough in relatively low concentrations. Below is a short list of foods with their corresponding phytoestrogen content,  as reported in a paper published by researchers in Canada. The Canadian researchers analyzed 121 food types including fruits, vegetables, herbs, grains, nuts and oils for their estrogen content. The food types, as reported from the study, with the highest total phytoestrogen content are listed in the two tables below.

Besides the amount, the composition of phytoestrogens varies from plant to plant. For example, isoflavones are found in high concentration in soy bean and soy bean food products (eg. tofu) where as lignans are mainly found in flax seed.

Table 1. Foods high in phytoestrogens content. The total phytoestrogen content is the sum of isoflavones (genistein, daidzein, glycitein, formononetin), lignans (secoisolariciresinol, matairesinol, pinoresinol, lariciresinol), and coumestan (coumestrol). (1 µg = 0.000001 g)