Phytoestrogens are estrogen hormone-like chemicals found in plants. Phytoestrogens comprise mostly isoflavones, flavones, coumestans and lignans. The former three are flavonoids. 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.

Several studies show that phytoestrogens have potential health benefits such as reducing risks of incidence 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. Phytoestrogens formulations are used by women in menopause as alternative or compelementary options to hormonal replacement therapy (HRT) for fear of side-effects or other considerations.

Estrogen is available in medically formulated pills. However, dietary estrogen (phytoestrogen) can also be found naturally in wide variety of plant-based foods, with the the level varying depending on the source. Below is a short list of phytoestrogen containing foods analyzed by researchers in Canada. The Canadian researchers analyzed 121 food types including fruits, herbs, grains, nuts and oils. The food types with the highest total phytoestrogen content are listed in the two tables below. Nuts, oil seeds and soy food products are the richest sources of phytoestrogens according to the report.

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).