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Isoflavones

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Introduction

Isoflavones are compounds found in many different plants. They are found most in soy products. Isoflavones mimic estrogen. They have been used to ease symptoms of menopause and lower blood pressure. Isoflavones have also been used to lower the risk of some types of cancer. They can be taken as a pill or powder.

Dosages

40 to 80 milligrams daily

What Research Shows

Likely Effective

Body weight —likely to reduce body weight, fasting glucose, and insulin level in postmenopausal women A1
Breast cancer—likely to lower the risk in pre- and post-menopausal women C1
Colorectal cancer—may lower the risk D1
High Blood Pressure—likely to lower blood pressure E1, E2
Menopause—likely to ease hot flashes and improve memory G1-G6
Obesity—likely to reduce body mass in women H1
Osteoporosis—likely to increase bone mineral density in women I1, I2

May Be Effective

Type 2 diabetes —may modestly lower risk in men and women who eat low to moderate amounts of soy J1

Unlikely to Be Effective

High cholesterol—unlikely to lower cholesterol F1

Not Enough Data to Assess

Bone health B1

Editorial process and description of evidence categories can be found at EBSCO NAT Editorial Process.

Safety Notes

It is likely safe to take isoflavones in small doses for a short time. Not enough studies have been done to say whether it is safe to use for a long period. Women who are pregnant or breastfeeding should not take large doses of isoflavones.

Interactions

Talk to your doctor about any supplements or therapy you would like to use. Some can interfere with treatment or make conditions worse.

References►

A. Body Weight

A1. Zhang YB, Chen WH, et al. Soy isoflavone supplementation could reduce body weight and improve glucose metabolism in non-Asian postmenopausal women--a meta-analysis. Nutrition. 2013 Jan;29(1):8-14.

B. Bone Health

B1. Castelo-Branco C, Cancelo Hidalgo MJ. Isoflavones: effects on bone health. Climacteric. 2011 Apr;14(2):204-211.

C. Breast Cancer

C1. Fritz H, Seely D, et al. Soy, red clover, and isoflavones and breast cancer: a systematic review. PLoS One. 2013 Nov 28;8(11):e81968.

C2. Chen M, Rao Y, et al. Association between soy isoflavone intake and breast cancer risk for pre- and post-menopausal women: a meta-analysis of epidemiological studies. PLoS One. 2014 Feb 20;9(2):e89288.

D. Colorectal Cancer

D1. Yu Y, Jing X, et al. Soy isoflavone consumption and colorectal cancer risk: a systematic review and meta-analysis. Sci Rep. 2016 May 12;6:25939.

E. High Blood Pressure

E1. Taku K, Lin N, et al. Effects of soy isoflavone extract supplements on blood pressure in adult humans: systematic review and meta-analysis of randomized placebo-controlled trials. J Hypertens. 2010 Oct;28(10):1971-1982.

E2. Liu XX, Li SH, et al. Effect of soy isoflavones on blood pressure: a meta-analysis of randomized controlled trials. Nutr Metab Cardiovasc Dis. 2012;22(6):463-470.

F. High Cholesterol

F1. Qin Y, Niu K, et al. Isoflavones for hypercholesterolaemia in adults. Cochrane Database Syst Rev. 2013;(6):CD009518.

G. Menopause

G1. Jacobs A, Wegewitz U, et al. Efficacy of isoflavones in relieving vasomotor menopausal symptoms - A systematic review. Mol Nutr Food Res. 2009 Sep;53(9):1084-1097.

G2. Taku K, Melby MK, et al. Extracted or synthesized soybean isoflavones reduce menopausal hot flash frequency and severity: systematic review and meta-analysis of randomized controlled trials. Menopause. 2012;19(7):776-790.

G3. Thomas AJ, Ismail R, et al. Effects of isoflavones and amino acid therapies for hot flashes and co-occurring symptoms during the menopausal transition and early postmenopause: a systematic review. Maturitas. 2014 Aug;78(4):263-276.

G4. Cheng PF, Chen JJ, et al. Do soy isoflavones improve cognitive function in postmenopausal women? A meta-analysis. Menopause. 2015;22(2):198-206.

G5. Ghazanfarpour M, Latifnejad Roudsari R, et al. Topical administration of isoflavones for treatment of vaginal symptoms in postmenopausal women: A systematic review of randomised controlled trials. J Obstet Gynaecol. 2015;35(8):783-787.

G6. Li L, Lv Y, et al. Quantitative efficacy of soy isoflavones on menopausal hot flashes. Br J Pharmacol. 2015;79(4):593-604.

G7. Ghazanfarpour M, Sadeghi R, et al. The application of soy isoflavones for subjective symptoms and objective signs of vaginal atrophy in menopause: A systematic review of randomised controlled trials. J Obstet Gynaecol. 2016;36(2):160-171.

H. Obesity

H1. Akhlaghi M, Zare M, et al. Effect of Soy and Soy Isoflavones on Obesity-Related Anthropometric Measures: A Systematic Review and Meta-analysis of Randomized Controlled Clinical Trials. Adv Nutr. 2017 Sep 15;8(5):705-717.

I. Osteoporosis

I1. Ricci E, Cipriani S, et al. Soy isoflavones and bone mineral density in perimenopausal and postmenopausal Western women: a systematic review and meta-analysis of randomized controlled trials. J Womens Health (Larchmt). 2010 Sep;19(9):1609-1617.

I2. Wei P, Liu M, et al. Systematic review of soy isoflavone supplements on osteoporosis in women. Asian Pac J Trop Med. 2012 Mar;5(3):243-248.

J. Type 2 Diabetes

J1. Ding M, Pan A, et al. Consumption of soy foods and isoflavones and risk of type 2 diabetes: a pooled analysis of three US cohorts. Eur J Clin Nutr. 2016 Dec;70(12):1381-1387.

Last reviewed February 2020 by EBSCO NAT Review Board Eric Hurwitz, DC
Last Updated: 5/27/2020

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