{"ok":true,"entry":{"slug":"soy-isoflavones","kind":"supplement","name":"soy isoflavones","aliases":["genistein","daidzein","isoflavones"],"brands_sg":["NOW Foods","Nutricost","Swanson","Life Extension","21st Century"],"class":"phytoestrogen","tags":["womens-health","bone-joint"],"use_for":"menopausal hot flushes and postmenopausal bone density","use_after":"daily","use_duration":"pooled trials had a median duration of 24 weeks","take_with":null,"pros":["nccih: probably helps postmenopausal bone density","2024 meta-analysis of 63 rcts: bmd up at 3 sites","18 rcts, 40–200 mg/day: no effect on thyroid hormones"],"cons":["nccih: supplement form not shown to cut cancer risk","hot-flash efficacy disputed; nams does not endorse it","only 1 of 4 rcts lasting ≥2 years saw bmd improve"],"dose_note":"a 2012 meta-analysis of 13 rcts concluded that 50 mg a day of total isoflavones works if about 20 mg of it is genistein; the 2024 bone meta-analysis of 63 rcts found benefit where the intervention contained ≥50 mg/day genistein; across the 40 rcts pooled by viscardi et al. the median dose was 75 mg/day for a median of 24 weeks","dosage":{"ul":null,"unit":"mg","fda_dv":null,"rda_ai":null,"ul_status":"none_established","population":"general adult","hsa_max_daily":null},"ul_status":"none_established","sg_class":null,"cautions":["soy allergy — nccih notes some people are allergic to soy","pregnancy — nccih: amounts above those in food may be unsafe","breast cancer — nccih: supplements not shown to lower risk","not listed in hsa annex a or b (oct 2025) — not a clearance"],"clashes":[{"src":["nccih_soy_interactions"],"note":"nccih reports interactions with high-tyramine soy foods such as tofu and soy sauce; this is a soy-food effect, not shown for isoflavone tablets","with":"monoamine oxidase inhibitors (MAOIs)"}],"sources":[{"id":"nccih_soy_what","url":"https://www.nccih.nih.gov/health/soy","label":"NCCIH — Soy (what soy supplements contain)","quote":"Soy supplements may contain soy protein, isoflavones (compounds similar in structure to the hormone estrogen), or other components.","accessed":"2026-08-27"},{"id":"nccih_soy_hotflash","url":"https://www.nccih.nih.gov/health/soy","label":"NCCIH — Soy (menopausal hot flashes)","quote":"Soy isoflavone supplements or soy protein may help to reduce the frequency and severity of menopausal hot flashes, but the effect may be small.","accessed":"2026-08-27"},{"id":"nccih_soy_bone","url":"https://www.nccih.nih.gov/health/soy","label":"NCCIH — Soy (bone density)","quote":"Soy isoflavones probably have a beneficial effect on bone density in postmenopausal women.","accessed":"2026-08-27"},{"id":"nccih_soy_breast","url":"https://www.nccih.nih.gov/health/soy","label":"NCCIH — Soy (breast cancer)","quote":"soy products in supplement form have not been shown to reduce breast cancer risk.","accessed":"2026-08-27"},{"id":"nccih_soy_safety","url":"https://www.nccih.nih.gov/health/soy","label":"NCCIH — Soy (side effects and allergy)","quote":"Side effects of soy may include bloating, constipation, diarrhea, and nausea. Some people are allergic to soy.","accessed":"2026-08-27"},{"id":"nccih_soy_pregnancy","url":"https://www.nccih.nih.gov/health/soy","label":"NCCIH — Soy (pregnancy and breastfeeding)","quote":"The use of soy during pregnancy may be unsafe in amounts greater than those commonly found in foods.","accessed":"2026-08-27"},{"id":"nccih_soy_interactions","url":"https://www.nccih.nih.gov/health/soy","label":"NCCIH — Soy (interactions with medications)","quote":"Interactions between certain soy products containing high amounts of tyramine (such as tofu and soy sauce), and monoamine oxidase inhibitors … have been reported.","accessed":"2026-08-27"},{"id":"iso_bmd2024","url":"https://europepmc.org/article/PMC/PMC12245442","label":"Perspective: Isoflavones — Intriguing Molecules but Much Remains to Be Learned about These Soybean Constituents (Adv Nutr 2025) — bone mineral density","quote":"a meta-analysis of 63 RCTs … showed that in postmenopausal women, isoflavones significantly improved BMD at the lumbar spine, femoral neck, and distal radius … of the 4 longer-term (≥2 y) RCTs … only 1 reported BMD improved.","accessed":"2026-08-27"},{"id":"iso_taku2012","url":"https://europepmc.org/article/PMC/PMC12245442","label":"Adv Nutr 2025 isoflavones perspective — hot-flash dose threshold (Taku 2012 meta-analysis of 13 RCTs)","quote":"These authors concluded that taking 50 mg/d total isoflavones is efficacious if at least ∼20 mg that amount is genistein.","accessed":"2026-08-27"},{"id":"iso_hotflash_dispute","url":"https://europepmc.org/article/PMC/PMC12245442","label":"Adv Nutr 2025 isoflavones perspective — professional society positions","quote":"With respect to hot flash alleviation, there continues to be disagreement about the efficacy of isoflavones … because of the variable findings, the North American Menopause Society does not endorse isoflavones.","accessed":"2026-08-27"},{"id":"iso_viscardi","url":"https://europepmc.org/article/PMC/PMC12245442","label":"Adv Nutr 2025 isoflavones perspective — Viscardi et al. systematic review of 40 RCTs on estrogenicity","quote":"in postmenopausal women, isoflavones (median trial duration, 24 wk; median isoflavone dose, 75 mg/d) were without significant effect on endometrial thickness, vaginal maturation index, and circulating levels of follicle-stimulating hormone and estradiol","accessed":"2026-08-27"},{"id":"iso_thyroid","url":"https://europepmc.org/article/PMC/PMC12245442","label":"Adv Nutr 2025 isoflavones perspective — thyroid function","quote":"a meta-analysis of 18 RCTs published in 2019 showed that neither soy nor isoflavone intake (doses ranging from 40 to 200 mg/d) affects circulating levels of free thyroxine or free triiodothyronine","accessed":"2026-08-27"},{"id":"hsa_prohibited_2025","url":"https://file.go.gov.sg/hsa-chp-prohibited-restricted-ing-guidelines.pdf","label":"HSA — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev. No. 001 (Oct 2025)","quote":"The objective of this guideline is to highlight the substances of concern when used in HS and TM and is not meant to be an exhaustive list","accessed":"2026-08-27"},{"id":"iherb_sg","url":"https://sg.iherb.com/c/soy-isoflavones","label":"iHerb Singapore — Soy Isoflavones category (default order, 1 - 14 of 14 results); first 5 distinct brands in page order","quote":"NOW Foods, Soy Isoflavones, 120 Veg Capsules … Nutricost, Soy Isoflavones, 150 mg … Swanson Vitamins, Soy Isoflavones, 750 mg … Life Extension, Soy Isoflavones … 21st Century, Soy Isoflavones Extract, Standardized","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:31.341231+08:00"},"disclaimer":"kozen-x is not a medical device and does not give medical advice. it lists what published sources have written down. absence of a record is not the same as safe."}