Phytoestrogens

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Phytoestrogens , also called phytoestrogens , are secondary plant substances , which include isoflavones and lignans . They are not estrogens in the chemical sense, but only have a structural similarity to them. This similarity enables a binding to estrogen receptors , whereby an estrogenic or anti-estrogenic effect can be achieved, d. that is, they act as endocrine disruptors . The best-known phytoestrogens are the isoflavones genistein , daidzein and coumestrol .

discovery

The first plant whose phytoestrogenic effect has been passed down is the sylphion ( Ferula historica ). It was used as a contraceptive , and so was the demand for it that it became extinct in the 2nd or 3rd century AD due to overuse.

In 1926, the chemists Loewe and Spohr succeeded for the first time in detecting the phytoestrogen estriol in pussy willow (200 mouse units (ME) estrogenic activity per kg fresh substance). In the following years several of these substances were found in various plants, such as B. palm kernels, rhubarb roots and red clover detected. Bradbury and White presented 36 different plant estrogens in 1954.

In 1930, pastures in Western Australia were made available to sheep farmers, including ground clover (Trifolium subterraneum L.). In 1941 the most severe fertility disorders up to sterility were observed in the female animals, which could be attributed to the phytoestrogens in the ground clover. The male animals showed a strong enlargement of the accessory sex glands, which often led to death. The same damage also occurred to the pasture plants alfalfa and red clover and could also be detected in cattle. In 1965, Thain reported on herd sterility of Jersey cattle in Tasmania, where the willow scar consisted of up to 80% ground clover. Furthermore, in 1966 Lotan and Adler in Israel demonstrated a clear connection between the feeding of alfalfa and cycle disorders in cattle. Fungal attack on the plants and ensiling also seem to greatly increase the estrogen effect of the plants. In alfalfa, leaf spot diseases caused abnormally high phytoestrogen levels (Krause 1970).

Occurrence in food

Soybeans and products made from them are particularly rich in the precursors of isoflavones that are active in the human body . Lignans are found mainly in flaxseed . Other sources of phytoestrogens are legumes , grain bran, and grain. They are also found in slightly lower concentrations in many types of vegetables and fruits, seeds, hops, sage, tea and some alcoholic beverages such as beer, wine and bourbon (whiskey). The level of phytoestrogen content in a food is also influenced by the variety, climate, harvest time and fruit ripeness.

Food Isoflavones mg / 100g (fresh weight) Isoflavones mg / 100g (dry weight)
Soy flour 171 173
Soy flour defatted 155
Soybeans 50 60-145 50-150
Soy nuts 149
Natto 82
Miso 60 77
red wine 30-50
beer 15-50
tofu 14-33 15-50
Yuba 45
soy milk 6.6 4.7-9.7
Soy sauce 5.2
liquorice 0.9
Peas 0-7.3
Beans 0-6.3
Soybean oil 0
Food Lignans µg / 100 g
linseed 370,000 371,100 384,500
Pumpkin seeds 20,300 21,400
Strawberries 1,578
Olives 1,254
Tea, black 1,100
cranberry 1,054
red wine 1,000
Sunflower seeds 818
Oat bran 790
Pumpkin 695
Wheat bran 664
Sesame seeds 661
blackberry 569
garlic 520
peanuts 460
lenses 457
asparagus 442
broccoli 256 437
Wheat , whole grain 410
Carrots 381
sweet potato 336
Apricot , dried 328
nuts 96-257
Soybeans 10-200
rye 112
barley 58
Food Coumestrol µg / 100 g
Alfalfa sprouts 1,197
Mung bean spr. 685
Soybean sprout 537
Pinto beans 301
Food Formononetin µg / 100 g
Alfalfa sprouts 1,126
liquorice 1,493
Green beans 1055
Bean sprouts 187

Ecological importance

A plant species that produces phytoestrogens has the advantage that the population of its predators , e.g. B. sheep and birds, by the fertility-reducing estrogenic effect is kept within limits. This gives the species a greater chance of survival. However, this is only a secondary ecological effect, as it does not protect the individual plant from the predator itself. The essential biological importance lies in the peculiarity of these polyphenol compounds as coloring, tanning and bittering substances , which make the plants inedible or difficult to digest or make them appear off-putting. Many phytoestrogens are also microbicides : They protect the plant from fungi and bacteria.

Health effects

The health significance of phytoestrogens is currently the subject of controversy. On the one hand, they are said to have positive effects on health and life expectancy, on the other hand there are also indications of negative properties in excessively high amounts in the diet. While soy-based baby food , which contains a high proportion of phytoestrogens, is quite common in the USA , such preparations are only available with a prescription in Germany. It is currently agreed that in adults, an amount that is normally ingested with food is relatively safe and can even be healthy. In a communication from the Federal Institute for Risk Assessment (BfR), the latter agrees with the assessment of the European Food Safety Authority (EFSA) that if the dosage and duration recommended by EFSA are adhered to, the consumption of food supplements with isolated isoflavones in women without existing estrogen-dependent diseases is in during or after menopause can be regarded as reasonably safe. However, in order to clarify the presence of any estrogen-dependent diseases that may be present, the BfR recommends seeking medical advice before taking such preparations.

Health-promoting effects: Due to their ability to bind to estrogen receptors and thus trigger effects similar to those of the body's own estrogens, phytoestrogens are said to have the ability to alleviate menopausal symptoms and reduce the risk of osteoporosis . Phytoestrogens are therefore comparable to the effects of hormone replacement therapies .

Asian women who frequently take phytoestrogens such as genistein through soy products have a roughly 25% lower risk of dying from breast cancer than other women of comparable age and body condition. In addition, it has long been known that the common epithelial breast cancer variant is hormone-dependent and that its growth is therefore stimulated by estrogens. This can be seen in various phenomena: women who do not produce estrogens do not get breast cancer; after menopause , the risk drops significantly; Hormone replacement therapy in menopause has been linked to a significant increase in breast cancer risk; Anti-estrogens are part of breast cancer therapy. One can therefore assume that starting phytoestrogens in childhood, as indicated by an animal study, and the resulting protection against natural estrogens is responsible for the corresponding effect - also against prostate cancer.

There are also potential health risks associated with taking phytoestrogens. It is most commonly associated with infertility and developmental disorders. For example, a one-sided diet with a certain clover that contains phytoestrogens will reduce the fertility of sheep. There are also a number of other studies with wild animals and domestic animals that support the results. Laboratory studies have shown that a phytoestrogen-rich diet can have negative effects on the fertility of laboratory animals for life. In addition, the differentiation of organs before and after birth can be disturbed by high doses of certain phytoestrogens and the risk of uterine cancer increases.

In a study published in 2013 by the American National Birth Defects Prevention Study, a reduced risk of giving birth to an infant with penile hypospadias was found with increased consumption of phytoestrogens. However, more research on the subject is needed to confirm these data. In addition, there are indications that children who were fed soy-based infant formula have more allergies and menstrual problems later than those who received cow's milk-based formula. With regard to the allergy risk in particular, one has to ask hypothetically whether the ingredients of soy can trigger later allergies and whether physiological ingredients in cow's milk protect against it.

It is now assumed that the gynecomastia that occurs with regular beer consumption is at least partially due to phytoestrogens contained in the beer, since the hops used to make beer contain small amounts of these substances that act like estrogens. However, what is known as false gynecomastia also occurs in the context of obesity , as is often observed in beer drinkers. This can be combined with real gynecomastia (actually enlarged mammary glands), since (especially intra- abdominal ) fat tissue has the ability to convert androgens into estrogens.

Web links

  • Phytoestrogens on e.hormone , a website of the Tulane / Xavier Center for Bioenvironmental Research (English)

Individual evidence

  1. ↑ Arno Hennig (Ed.): Minerals, Vitamins, Ergotropics. Deutscher Landwirtschaftsverlag, Berlin 1972. P. 407ff
  2. ↑ a b c d e f g h i j k l m n o p q r s t u v w x y z aa ab ac ad ae Regina Verena Piller: Phytoestrogens in the diet and their influence on the risk of breast cancer (dissertation ). In: http://mediatum.ub.tum.de/ . Technical University of Munich, June 12, 2006, accessed on August 2, 2020 .
  3. ↑ a b c d e f Angela Mörixbauer: Soy, soy isoflavones and health effects. In: https://www.ernaehrungs-umschau.de/ . Nutrition review, March 2019, accessed on August 2, 2020 .
  4. ↑ a b c d e f g h i j k l m n o Dr. oec. troph. Antonie Danz: Phytoestrogens - plant substances with hormonal effects. In: https://www.ugb.de/ . The Association for Independent Health Advice (UGB), 2015, accessed on August 2, 2020 .
  5. ↑ a b c d e f g h Examination for estrogen-like substances with a bio test. In: https://www.laves.niedersachsen.de/ . Lower Saxony State Office for Consumer Protection and Food Safety, 2011, accessed on August 2, 2020 .
  6. ↑ a b c d Tulane University's endocrine disruption tutorial about Phytoestrogens
  7. ↑ Food supplements with isolated isoflavones (PDF; 41 kB) BfR Communication No. 043/2015 of November 16, 2015.
  8. ^ Adlercreutz, Mazur: Phyto-oestrogens and Western diseases . 1997, PMID 9187225
  9. ↑ Messina et al .: Soy foods and soybean isoflavones and menopausal health . 2002, PMID 12557810
  10. ↑ Genistein - model material for describing the endocrine effects of phytoestrogens . Gesellschaft Deutscher Chemiker, BUA-Stoffbericht 222. Wissenschaftliche Verlagsgesellschaft S. Hirzel, Stuttgart 2000, ISBN 3-7776-1037-2 , s. innovations-report.de
  11. ^ Anthony S. Fauci et al .: Harrison's Principles of Internal Medicine , 17th Edition. 2008, ISBN 0-07-146633-9 , pp. 563, 567
  12. ↑ Lamartiniere et al .: Genistein studies in rats: potential for breast cancer prevention and reproductive and developmental toxicity . 1998, PMID 9848507
  13. ↑ HW Bennetts, EJ Underwood: The estrogenic effects of subterranean clover (Trifolium subterraneum); Uterine maintenance in the ovariectomized ewe grazing on clover . In: Aust J Exp Biol Med Sci , 29 (4), 1951, pp. 249-253
  14. ↑ Leopold et al .: Phytoestrogens: adverse effects on reproduction in California quail . 1976, PMID 1246602
  15. ↑ Setchell et al .: Dietary estrogens - a probable cause of infertility and liver disease in captive cheetahs . 1987, PMID 3297906
  16. ↑ Carmichael SL, Cogswell ME, Ma C, Gonzalez-Feliciano A, Olney RS, Correa A, Shaw GM: Hypospadias and maternal intake of phytoestrogens . 2013, PMID 23752918
  17. ↑ JS Gavaler: Alcoholic beverages as a source of estrogens . In: Alcohol health and research world , 1998, PMID 15706799 , full text (PDF; 153 kB)
  18. ↑ ER Rosenblum et al .: Isolation and identification of phytoestrogens from beer . In: Alcohol Clin Exp Res , 1992, PMID 1443418
  19. ↑ SR Milligan et al .: Identification of a potent phytoestrogen in hops (Humulus lupulus L.) and beer . In: J Clin Endocrinol Metab , 1999, PMID 10372741