Phytoestrogens

Related Terms

8-Prenylnaringenin (8-PN), biochanin A, coumestans, coumestrol, daidzein, enterodiol, enterolactone, equol, flax phytoestrogens, flaxseed, formononetin, genistein, glycitein, hop extract, Humulus lupulus L., isoflavones, isoflavonoid phytoestrogen, lignans, matairesinol, O-desmethylangolensin (O-DMA), prenylflavonoids, Pueraria lobata (kudzu), red clover, secoisolariciresinol diglucoside (SDG), soy.
Combination product examples: MenoHop?, PHYTO SOYA?, Promensil?, Rimostil?, SoyaVital?.
Note: This review does not include mycoestrogens, which are estrogenic fungal products and not intrinsic components of plants. They are found in pasture grasses and legumes infected by the fungal genus Fusarium.

Background

The word "phytoestrogen" is derived from phyto, meaning "plant" and estrogen, because of the ability of these compounds to affect estrogenic activity in the body. Phytoestrogens are a diverse group of polyphenolic, nonsteroidal plant compounds that may cause both estrogenic and antiestrogenic effects. The estrogenic effects of phytoestrogens are similar, although less intense, than those of estrogens made by the human body. There are reportedly approximately 300 plant species containing phytoestrogen compounds that have some degree of estrogen activity.
The three major classes of phytoestrogens are isoflavones, lignans, and coumestans. Isoflavones are prominent in soy-based foods. Lignans are minor components of cell walls and fibers of seeds, fruits, berries, vegetables, grains, and nuts. Linseed (flaxseed) is a rich source of lignans. The primary coumestan is coumestrol. It is found in alfalfa and clovers, and in low levels in soybeans and peas.
Several population studies have indicated that phytoestrogens have health benefits. These include possible protection against menopausal symptoms and osteoporosis, as well as a potential reduction in breast cancer, prostate cancer, and cardiovascular disease risks. Both isoflavone and lignan phytoestrogens may have antioxidant activity.

Evidence Table

These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. GRADE *


Evidence suggests that certain populations that consume large amounts of soy protein have lower cardiovascular morbidity and mortality. Soy protein has been reported to reduce serum lipid levels by up to 10%. Preliminary evidence suggests that soy protein is superior to isoflavones isolated from red clover for reduction of serum lipid levels. Additional research is needed in this area.

 B


Evidence suggests that certain populations that consume large amounts of soy protein have lower cardiovascular morbidity and mortality. Soy protein has been reported to reduce serum lipid levels by up to 10%. Preliminary evidence suggests that soy protein is superior to isoflavones isolated from red clover for reduction of serum lipid levels. Additional research is needed in this area.

 B


Foods rich in phytoestrogens may help alleviate symptoms of menopause, such as vaginal dryness, burning, itching, painful intercourse, and decreased interest in sex. Additional, well-designed studies are needed before firm conclusions may be made.

 B


Foods rich in phytoestrogens may help alleviate symptoms of menopause, such as vaginal dryness, burning, itching, painful intercourse, and decreased interest in sex. Additional, well-designed studies are needed before firm conclusions may be made.

 B


It has been theorized that phytoestrogens, such as isoflavonoids found in soy and red clover, may increase bone mineral density in postmenopausal women and reduce the risk of fractures. Further studies are required before a firm conclusion may be made.

 B


It has been theorized that phytoestrogens, such as isoflavonoids found in soy and red clover, may increase bone mineral density in postmenopausal women and reduce the risk of fractures. Further studies are required before a firm conclusion may be made.

 B


Some evidence suggests that isoflavones may have a beneficial effect on cognitive function in postmenopausal women. Additional research is needed in this area.

 C


Some evidence suggests that isoflavones may have a beneficial effect on cognitive function in postmenopausal women. Additional research is needed in this area.

 C


Multiple studies have shown that dietary intake of phytoestrogens derived from soy, lignans, or red clover reduces the risk of osteoporosis in postmenopausal women by inhibiting bone resorption, stimulating bone formation, preventing bone loss, and increasing bone mineral content. Additional studies are needed before a conclusion can be made.

 C


Multiple studies have shown that dietary intake of phytoestrogens derived from soy, lignans, or red clover reduces the risk of osteoporosis in postmenopausal women by inhibiting bone resorption, stimulating bone formation, preventing bone loss, and increasing bone mineral content. Additional studies are needed before a conclusion can be made.

 C


Approximately 30% of women afflicted with migraine have headaches associated with menstruation. Preliminary research suggests that a combination product containing soy, dong quai, and black cohosh may be effective in preventing menstrual migraines. Further research with phytoestrogens alone is needed.

 C


Approximately 30% of women afflicted with migraine have headaches associated with menstruation. Preliminary research suggests that a combination product containing soy, dong quai, and black cohosh may be effective in preventing menstrual migraines. Further research with phytoestrogens alone is needed.

 C


In laboratory research, phytoestrogens had anticarcinogenic properties, such as growth arrest, and may have caused programmed cell death in prostate cancer cells. Additional research is needed in this area.

 C


In laboratory research, phytoestrogens had anticarcinogenic properties, such as growth arrest, and may have caused programmed cell death in prostate cancer cells. Additional research is needed in this area.

 C
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)
* Key to grades

A: Strong scientific evidence for this use
B: Good scientific evidence for this use
C: Unclear scientific evidence for this use
D: Fair scientific evidence for this use (it may not work)
F: Strong scientific evidence against this use (it likley does not work)

Tradition / Theory

The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.

Dosing

Adults (18 years and older)
For cardiovascular risk reduction (postmenopausal), phytoestrogens derived from 40 grams of crushed flaxseed have been taken by mouth daily for two months. The isoflavone genistein has been taken by mouth at a dose of 54 milligrams daily for 6-12 months. Ninety milligrams of isoflavones (1:1:0.2 genistein:daidzein:glycitein) has been taken by mouth daily in two divided doses for six weeks. Isoflavones from Pueraria lobata (kudzu) have been taken by mouth in a daily dose of 100 milligrams for three months. Isoflavonoids (114 milligrams) have been taken by mouth daily for three months. Phytoestrogens (30 grams of soy protein, 132 milligrams of isoflavones) have been taken by mouth daily for 12 weeks.
For cognitive function, 100 milligrams of isoflavones from Pueraria lobata (kudzu) has been taken by mouth daily for three months.
For menopausal symptoms, 100 or 250 micrograms of an extract of hops (Humulus lupulus L.) standardized to 8-prenylnaringenin (8-PN) have been taken by mouth daily for 12 weeks. Daily doses of Promensil? (82 milligrams of total isoflavones) or Rimostil? (57 milligrams of total isoflavones) have been taken by mouth for 12 weeks. Phytoestrogens in the form of isoflavones have also been taken by mouth in doses of 35 milligrams (one capsule of SoyaVital?) daily for 12 weeks. Phytoestrogens in the form of isoflavones have been taken by mouth in a dose of 35 milligrams daily in two divided doses (one PHYTO SOYA? capsule containing 175 milligrams of soy extract corresponding to 17.5 milligrams of isoflavones) for four months. Phytoestrogens in the form of isoflavones have also been taken by mouth in a dose of 118 milligrams daily in soy supplements for three months. Muffins containing 25 grams of soy (42 milligrams of isoflavones) or 25 grams of flaxseed (50 milligrams of lignans) have been taken by mouth daily for 16 weeks. Isoflavonoids have been taken by mouth in a dose of 114 milligrams daily for three months.
For osteoporosis prevention, 114 milligrams of isoflavonoids has been taken by mouth daily for three months. A daily dose of isoflavones from red clover (26 milligrams of biochanin A, 16 milligrams of formononetin, one milligram of genistein, and 0.5 milligram of daidzein) has been taken by mouth for one year. Genistein (54 milligrams) has been taken by mouth daily for one year.
For prostate cancer, 240 milligrams of clover phytoestrogens has been taken by mouth daily for two weeks prior to prostatectomy.

Safety

The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.

Interactions

Interactions with Drugs
Phytoestrogen therapy (with genistein) may increase the risk of bleeding when taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants (blood thinners) such as warfarin (Coumadin?) or heparin, antiplatelet drugs such as clopidogrel (Plavix?), and nonsteroidal anti-inflammatory drugs such as ibuprofen (Motrin?, Advil?) or naproxen (Naprosyn?, Aleve?).
Phytoestrogens derived from soy supplements or flaxseed may result in decreases in fasting blood sugar, fasting insulin levels, and insulin resistance. Caution is advised when using medications that may also lower blood sugar. Patients taking insulin or drugs for diabetes by mouth should be monitored closely by a qualified healthcare professional, including a pharmacist. Medication adjustments may be necessary.
Phytoestrogens may also interact with agents that affect the immune system, anticancer agents, anti-inflammatory agents, antimigraine agents, bisphosphonates, cardiovascular agents, estrogens, fertility agents, or lipid-lowering agents.

Attribution

This information is based on a systematic review of scientific literature edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (www.naturalstandard.com).

Bibliography

Berrino F, Bellati C, Secreto G, et al. Reducing bioavailable sex hormones through a comprehensive change in diet: the diet and androgens (DIANA) randomized trial. Cancer Epidemiol Biomarkers Prev 2001;10(1):25-33.
Chiechi LM, Putignano G, Guerra V, et al. The effect of a soy rich diet on the vaginal epithelium in postmenopause: a randomized double blind trial. Maturitas 2003;45(4):241-246.
Crisafulli A, Altavilla D, Marini H, et al. Effects of the phytoestrogen genistein on cardiovascular risk factors in postmenopausal women. Menopause 2005;12(2):186-192.
D'Anna R, Baviera G, Corrado F, et al. The effect of the phytoestrogen genistein and hormone replacement therapy on homocysteine and C-reactive protein level in postmenopausal women. Acta Obstet Gynecol Scand 2005;84(5):474-477.
Greany KA, Nettleton JA, Wangen KE, et al. Probiotic consumption does not enhance the cholesterol-lowering effect of soy in postmenopausal women. J Nutr 2004;134(12):3277-3283.
Heyerick A, Vervarcke S, Depypere H, et al. A first prospective, randomized, double-blind, placebo-controlled study on the use of a standardized hop extract to alleviate menopausal discomforts. Maturitas 2006;54(2):164-175.
Jayagopal V, Albertazzi P, Kilpatrick ES, et al. Beneficial effects of soy phytoestrogen intake in postmenopausal women with type 2 diabetes. Diabetes Care 2002;25(10):1709-1714.
Lemay A, Dodin S, Kadri N, et al. Flaxseed dietary supplement versus hormone replacement therapy in hypercholesterolemic menopausal women. Obstet Gynecol 2002;100(3):495-504.
Lissin LW, Oka R, Lakshmi S, et al. Isoflavones improve vascular reactivity in post-menopausal women with hypercholesterolemia. Vasc Med 2004;9(1):26-30.
Messina M. The endometrial effects of isoflavones: a discussion paper. Complement Ther Clin Pract 2008;14(3):212-214.
Mitchell JH, Cawood E, Kinniburgh D, et al. Effect of a phytoestrogen food supplement on reproductive health in normal males. Clin Sci (Lond) 2001;100(6):613-618.
Peeters PH, Slimani N, Van Der Schouw YT, et al. Variations in plasma phytoestrogen concentrations in European adults. J Nutr 2007;137(5):1294-1300.
Tuohy PG. Soy infant formula and phytoestrogens. J Paediatr Child Health 2003;39(6):401-405.
Unfer V, Casini ML, Gerli S, et al. Phytoestrogens may improve the pregnancy rate in in vitro fertilization-embryo transfer cycles: a prospective, controlled, randomized trial. Fertil Steril 2004;82(6):1509-1513.
Zava DT, Dollbaum CM, Blen M. Estrogen and progestin bioactivity of foods, herbs, and spices. Proc Soc Exp Biol Med 1998;217(3):369-378.