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 their concentration 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 associate phytoestrogens with reduced risks of breast cancer, prostate cancer and cardiovascular diseases. Other phytoestrogen health benefits are reduced osteoporosis (bone loss) and menopausal symptoms. Both flavonoid and lignan phytoestrogens also have antioxidant activity. Medical 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 phytoestrogens?
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 amount varying depending on the plant type. 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.
The type of phytoestrogens and their relative concentration varies from plant to plant. For example, isoflavone phytoestrogens are found in high concentration in soybean and soybean food products (eg. tofu) where as lignan phytoetrogens are mainly found in flax seed.
Canadian researchers analyzed 121 food types including fruits, vegetables, herbs, grains, nuts and oils for their phytoestrogen content. The food types, as reported in the study, with the highest total phytoestrogen content are listed in the two tables below.
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)
|Phytoestrogen food sources||Phytoestrogens content (µg/100g)|
|Soy protein powder||
|Mung bean sprouts||