Isoflavones

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Structural formula of isoflavone.

Isoflavones , also called isoflavonoids , are mostly yellowish colored plant dyes which, as derivatives of isoflavones, belong to the class of flavonoids . They are secondary plant substances that u. a. exercise a function for plant defense against pathogens .

The basic body isoflavone occurs in types of clover . Some of the better-known isoflavones are daidzein , as the glucoside daidzin in soy flour, genistein from soybeans and red clover , prunetin from the bark of plum trees , biochanin A from chickpeas , red clover and the like. a. Clover species, orobol, santal made of sandalwood , redwood, etc. a. Wooden, pratensein made of fresh red or meadow clover and iridine in some irises .

Some selected isoflavones and their structure
Surname structure R 5 R 7 R 3 ' R 4 '
Isoflavone Isoflavone num.svg -H -H -H -H
Daidzein -H -OH -H -OH
Genistein -OH -OH -H -OH
Prunetin -OH -OCH 3 -H -OH
Biochanin A -OH -OH -H -OCH 3
Orobol -OH -OH -OH -OH
Santal -OH -OCH 3 -OH -OH
Prateness -OH -OH -OH -OCH 3

effect

Like the lignans , the isoflavonoids have a weak sex hormonal effect on humans in high doses because of their chemical-structural similarity to the 17-keto steroids ( estrogen , androgens ). They are therefore also called phytoestrogens . In alternative medicine , women are recommended to consume flavonoids or soy preparations during menopause when they have hot flashes and sweats. A modest effect of isoflavones on hot flashes was described by the North American Menopause Society (NAMS) in 2016. In addition, a preventive effect for hormone-dependent cancers such as breast and prostate cancer is being discussed. Various long-term studies from Canada, the Netherlands and Japan have shown that high isoflavone levels in the blood correlate with a low rate of breast cancer. In addition, a meta-analysis of 35 studies showed that soy isoflavones significantly reduce the risk of breast cancer in the women examined in Asia, while this effect did not occur in Western countries. One of these studies, which was carried out on 334,850 women between 35 and 70 years of age, proves the safety of soy isoflavones.

For this reason, they are offered in countless dietary supplements .

However, approved drugs are not available on the German drug market because their effectiveness has not yet been proven. On the contrary, some doctors warn against excessive consumption of soy products and dietary supplements with isolated isoflavones, because flavonoids are suspected of inhibiting thyroid hormone production and causing goiter . Current clinical studies and various meta-analyzes and reviews, however, tend to confirm the positive effects of soy isoflavones and could not confirm this suspicion.

In a statement from the Federal Institute for Risk Assessment (BfR) from 2007, considerable concerns were still expressed.

A scientific opinion from the European Food Safety Authority (EFSA) from 2015 states that there is no evidence that isoflavones in dietary supplements are harmful to postmenopausal women at the usual dosage. The Federal Institute for Risk Assessment (BfR) agreed with this view in 2017. The EFSA safety study shows in detail that isoflavones at a dose of 35 to 150 mg daily, taken in through food or supplements, do not have any negative effects on the breast, uterus and thyroid. The effects are obviously independent of the source: positive effects were achieved both with isoflavones from soy food and with soy and red clover extracts. In epidemiological studies it has been proven that phyto-osterogenic preparations have no growth-promoting effect on the breast or uterus.

Occurrence in food

Isoflavones are mainly found in soybeans and products made from them.

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

See also

Individual evidence

  1. ↑ a b entry on isoflavones. In: Römpp Online . Georg Thieme Verlag, accessed on June 20, 2014.
  2. ↑ The role of soy isoflavones in menopausal health: report of The North American Menopause Society. (PDF) Retrieved January 18, 2016 (English).
  3. ↑ Beatrice A. Boucher, Michelle Cotterchio a. a .: Use of isoflavone supplements is associated with reduced postmenopausal breast cancer risk. In: International Journal of Cancer. 132, 2013, p. 1439, doi: 10.1002 / ijc.27769 .
  4. ↑ Meinan Chen, Yanhua Rao et al .: Association between Soy Isoflavone Intake and Breast Cancer Risk for Pre- and Post-Menopausal Women: A Meta-Analysis of Epidemiological Studies. In: PLoS ONE. 9, 2014, p. E89288, doi: 10.1371 / journal.pone.0089288 .
  5. ^ R. Zamora-Ros, P. Ferrari, CA González, A. Tjønneland, A. Olsen, L. Bredsdorff, K. Overvad, M. Touillaud, F. Perquier, G. Fagherazzi, A. Lukanova, K. Tikk, K. Aleksandrova, H. Boeing, A. Trichopoulou, D. Trichopoulos, V. Dilis, G. Masala, S. Sieri, A. Mattiello, R. Tumino, F. Ricceri, HB Bueno-de-Mesquita, PH Peeters, E. Weiderpass, G. Skeie, D. Engeset, V. Menéndez, N. Travier, E. Molina-Montes, P. Amiano, MD Chirlaque, A. Barricarte, P. Wallström, E. Sonestedt, M. Sund, R Landberg, KT Khaw, NJ Wareham, RC Travis, A. Scalbert, HA Ward, E. Riboli, I. Romieu: Dietary flavonoid and lignan intake and breast cancer risk according to menopause and hormone receptor status in the European Prospective Investigation into Cancer and Nutrition (EPIC) Study. In: Breast Cancer Research and Treatment . Volume 139, Number 1, May 2013, pp. 163-176, doi: 10.1007 / s10549-013-2483-4 . PMID 23572295 .
  6. ↑ Isoflavones and L-Carnitine: more risk than benefit. In: Pharmaceutical newspaper online. 26/2010.
  7. ↑ Mn. Chen, Cc. Lin, cf. Liu: Efficacy of phytoestrogens for menopausal symptoms: a meta-analysis and systematic review. In: Climacteric. 18, 2015, p. 260, doi: 10.3109 / 13697137.2014.966241 .
  8. ↑ A. Lethaby, J. Marjoribanks, F. Kronenberg, H. Roberts, J. Eden, J. Brown: Phytoestrogens for menopausal vasomotor symptoms. In: Cochrane Database of Systematic Reviews. Issue 12, 2013, Art. No .: CD001395. doi: 10.1002 / 14651858.CD001395.pub4 .
  9. ↑ BfR: Isoflavones - BfR
  10. ↑ Isoflavones in food supplements for postmenopausal women: no evidence of harmful effects. Retrieved November 9, 2015.
  11. ↑ Isoflavones are safe. (No longer available online.) Archived from the original on January 25, 2016 ; Retrieved January 25, 2016 .
  12. ↑ EFSA confirms the safety of isoflavones. (PDF) Retrieved January 19, 2016 (English).
  13. ↑ M. Lipovac, P. Chedraui, C. Gruenhut, A. Gocan, C. Kurz, B. Neuber, M. Imhof: The effect of red clover isoflavone supplementation over vasomotor and menopausal symptoms in postmenopausal women. In: Gynecological endocrinology: the official journal of the International Society of Gynecological Endocrinology. Volume 28, number 3, March 2012, pp. 203-207, doi: 10.3109 / 09513590.2011.593671 . PMID 21870906 . (PDF)
  14. ^ ED Faure, P. Chantre, P. Mares: Effects of a standardized soy extract on hot flushes: a multicenter, double-blind, randomized, placebo-controlled study. In: menopause. Volume 9, Number 5, Sep-Oct 2002, pp. 329-334. PMID 12218721 .
  15. ↑ a b c d e f 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 .
  16. ↑ 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 .
  17. ↑ a b c d e f 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 .
  18. ↑ a b c d Testing 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 .