Phytoestrogens as Pharma Foods
*Corresponding author: Charu Gupta
Gupta C, Prakash D, Gupta S. Phytoestrogens as pharma foods. Adv Food Technol Nutr Sci Open J. 2016; 2(1): 19-31. doi: 10.17140/ AFTNSOJ-2-127
©2016 Gupta C. This is an open access article distributed under the Creative Commons Attribution 4.0 International License (CC BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Phytoestrogens are a diverse group of plant-derived compounds that structurally or functionally mimic mammalian estrogens and show potential benefits for human health. They can serve as potential alternatives to the synthetic selective estrogen receptor modulators which are currently being used in hormone replacement therapy. Estrogens play many important physiological roles in men and women. In women, life is severely affected by a variety of estrogen-related conditions such as osteoporosis, cognitive and cardiovascular disease, increased risk of breast cancer and other symptoms that decrease the overall quality of life. Phytoestrogens are effective in maintaining bone mineral density, prevent bone loss, and help in the prevention and/or treatment of such health related problems. They can be classified as flavonoids, isoflavonoids, coumestans, stilbenes, lignans and terpenoids. The main isoflavones, genistein and daidzein found in soybean, can exist as glucosides or as aglycones, and are readily hydrolyzed in the gut to their aglycones. The aglycones are easily transported across intestinal epithelial cells. Terpenoids (ferutinine, tschimgine, and tschimganidine) found in the Umbelliferae family have estrogenic activities. The main dietary source of phytoestrogenic stilbenes is trans-resveratrol from red wine and peanuts. Plant-derived foods may be an adequate source for a variety of phytoestrogens capable of producing a range of pharmacological effects and protection from various life threatening diseases. This article provides the comprehensive information about the main groups of phytoestrogens, their food as well as herbal or botanical sources, potential health benefits and probable health hazards.
DES: Diethylstilbestrol; SECO: Secoisolariciresinol; ER: Estrogen receptors; SHBG: Soy-based infant formulas; PPARs: Peroxisome proliferator-activated receptors; CV: Corn oil vehicle; G: Genistein; SBIFs: Soy-based infant formulas; BD: Betadefensin-2; S1P: Sphingosine-1-phosphate; CAMP: Cathelicidin antimicrobial peptide; VDR: Vitamin D receptor; SERM: Selective Estrogen Receptor Modulator; CVD: Cardiovascular disease; LDL: Low Density Lipoprotein; HRT: Hormone Replacement Therapy; BMD: Bone Mineral Density; AD: Alzheimer’s Disease.
It was observed that Asian populations have lower rates of cardiovascular disease, menopausal symptoms, breast cancer (and other hormone dependent cancers), diabetes and obesity than Western populations.1 The diet of Asian populations revealed that soy is the major part of food in an Asian diet. This observation has fueled the widely held belief that consumption of soy foods reduces the risk of disease. Phytoestrogens were first observed in 1926,2 but it was unknown if they could have any effect in human or animal metabolism. In the 1940s, it was noticed for the first time that red clover (a phytoestrogens-rich plant) pastures had effects on the fecundity of grazing sheep.2,3
Phytoestrogens as the name suggests are the estrogens (xenoestrogens) that are derived from the plants and not generated within the endocrine system. They can be consumed by eating phytoestrogenic plants and so are also known as “dietary estrogens”. A phytoestrogen is a plant nutrient that is somewhat similar to the female hormone estrogen. Due to this similarity, lignans may have estrogenic and/or anti-estrogenic effects in the body.
They are a diverse group of naturally occurring nonsteroidal plant compounds that because of their structural similarity with estradiol (17-β-estradiol), have the ability to cause estrogenic or/and anti-estrogenic effects,2 by sitting in and blocking receptor sites against estrogen. Research has shown that phytoestrogens have many health benefits such as reduction in incidence of cardiovascular diseases, prostate cancer and breast cancer. They also provide protection against post menopausal diseases including osteoporosis. Besides, both phytoestrogens such as flavonoids and lignan also possess antioxidant activity.
The major groups of phytoestrogens include flavones, isoflavones, coumestans and lignans. The former three chemically are flavonoids. Phytoestrogens in particular isoflavones are found in high amounts in soybean and their products like tofu whereas lignans are mainly found in flax seed.
Dietary estrogen (phytoestrogen) are found in wide variety of food products (including herbs), even though the level varies depending on the source. The food products with the highest total phytoestrogen content are nuts and oil seeds followed by soy products (Tables 1 and 2). The total phytoestrogen content presented is the sum of isoflavones (genistein, daidzein, glycitein, formononetin), lignans (secoisolariciresinol, matairesinol, pinoresinol, lariciresinol), and coumestan (coumestrol).
Food Sources of Phytoestrogens
The main food sources rich in phytoestrogens are nuts and oilseeds, followed by soy products, cereals and breads, legumes, meat products and other processed foods that may contain soy, vegetables, fruits, alcoholic and nonalcoholic beverages. Flax seed and other oilseeds contained the highest total phytoestrogen content, followed by soybeans and tofu.4 The highest concentrations of isoflavones are found in soybeans and soybean products followed by legumes, whereas lignans are the primary source of phytoestrogens found in nuts and oilseeds (e.g. flax) and also found in cereals, legumes, fruits and vegetables.
Phytoestrogen (PE) content varies in different foods, and may vary significantly within the same group of foods (e.g. soy beverages, tofu) depending on processing mechanisms and type of soybean used.5 Legumes (in particular soybeans), whole grain cereals, and some seeds are high in phytoestrogens. Some other examples of foods that contain phytoestrogens are linseed (flax), Sesame seeds, Wheat berries, Fenugreek, Oats, Barley,