Generic Name: phytoestrogens
Brand and Other Names: isoflavones, daidzein, genistein, ipriflavone, ostivone, soy isoflavones
Drug Class: Herbals
What are phytoestrogens, and what are they used for?
Phytoestrogens are natural substances that are similar to estrogens, the human female sex hormones. Phytoestrogens are taken to compensate for the drop in estrogen levels in menopausal women and relieve menopausal vasomotor symptoms such as hot flashes and night sweats, and prevent bone loss and brittle bones (osteoporosis). Natural sources of phytoestrogens include soy and soy products, nuts, seeds, legumes, cereals, fruits, and vegetables.
Phytoestrogens are a group of polyphenolic non-steroidal compounds that are structurally or functionally similar to estradiol, one of the forms of estrogen. Phytoestrogens include flavones, isoflavones, lignans, and stilbenes, and the most common phytoestrogens such as isoflavones have estrogenic effects, although weaker than natural human estradiol.
Phytoestrogens work by binding to estrogen receptors, protein particles that respond to estrogen. By binding to estrogen receptors, phytoestrogens have weak estrogenic effects in menopausal women, but may reduce natural estrogen’s activity and have anti-estrogenic effects in premenopausal women. Phytoestrogens also have antioxidant properties, may stimulate new bone cell generation, and increase sex hormone binding globulin (SHBG) that transports sex hormones to the tissues in the body.
Studies indicate isoflavones may have some efficacy in reducing menopausal symptoms such as hot flashes and night sweats, protect against menopause-associated heart disease and bone loss (osteoporosis), and reduce the risk of breast cancer, however, results are mixed for prevention of other cancers. Phytoestrogens are used for many other conditions as well, however, there is insufficient scientific evidence to support many of these uses.
Suggested uses of phytoestrogens include:
- Menopausal symptoms
- Treatment and prevention of osteoporosis
- High cholesterol levels
- Cardiovascular disease
- Diabetes
- Hormone-dependent tumor
- Weight loss
- Skin health
- Cognitive function
What are the side effects of phytoestrogens?
Warnings
- Do not take phytoestrogen supplements if you are hypersensitive to any of the components in the formulation.
- Do not take phytoestrogens if you are pregnant.
- Phytoestrogens may have the potential for disrupting endocrine function.
- Taking large quantities of phytoestrogen supplements may affect fertility.
Common side effects of phytoestrogens include:
- Allergic reactions
- Abdominal pain
- Muscle pain (myalgia)
- Sleepiness
Call your doctor immediately if you experience any of the following symptoms or serious side effects while using this drug:
- Serious heart symptoms include fast or pounding heartbeats, fluttering in your chest, shortness of breath, and sudden dizziness;
- Severe headache, confusion, slurred speech, severe weakness, vomiting, loss of coordination, feeling unsteady;
- Severe nervous system reaction with very stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, tremors, and feeling like you might pass out; or
- Serious eye symptoms include blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.
This is not a complete list of all side effects or adverse reactions that may occur from the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may also report side effects or health problems to the FDA at 1-800-FDA-1088.
What are the dosages of phytoestrogens?
There are no established dosages for phytoestrogens.
Suggested dosing:
Isoflavones
- 40 mg orally once daily
- Menopausal symptoms: 34-120 mg/day
- Hypertension: 18 mg orally twice daily
- Lung cancer prevention: 8.3-83.2 mcg/day
Ipriflavone
- 200 mg orally 3 times a day
Dosage modifications
Creatinine clearance (CrCl) 40-80 mL/min
- 200 mg orally twice daily
CrCl below 40 mL/min
- 200 mg orally once daily
Overdose
- There is no reliable information on phytoestrogen overdose. In case of overdose, report your symptoms to the FDA.

SLIDESHOW
What Is Osteoporosis? Treatment, Symptoms, Medication See SlideshowWhat drugs interact with phytoestrogens?
Inform your doctor of all medications you are currently taking, who can advise you on any possible drug interactions. Never begin taking, suddenly discontinue, or change the dosage of any medication without your doctor’s recommendation.
- Phytoestrogens have no known severe or serious interactions with other drugs.
- Phytoestrogens have moderate interactions with at least 69 different drugs.
- Mild interactions of phytoestrogens include:
- anamu
- bazedoxifene/conjugated estrogens
- cimetidine
- conjugated estrogens
- conjugated estrogens, vaginal
- danshen
- devil's claw
- dexlansoprazole
- esomeprazole
- estradiol
- estrogens conjugated synthetic
- estrogens esterified
- estropipate
- famotidine
- ibuprofen/famotidine
- lansoprazole
- mestranol
- nizatidine
- omeprazole
- pantoprazole
- rabeprazole
- theophylline
The drug interactions listed above are not all of the possible interactions or adverse effects. For more information on drug interactions, visit the RxList Drug Interaction Checker.
It is important to always tell your doctor, pharmacist, or health care provider about all prescription and over-the-counter medications you use, as well as the dosage for each, and keep a list of the information. Check with your doctor or healthcare provider if you have any questions about the medication.
Pregnancy and breastfeeding
- There isn’t any reliable information on the safety of taking phytoestrogens during pregnancy. Avoid if you are pregnant.
- There is no information on whether phytoestrogens are excreted in breast milk, or their effects on breast milk production or on the breastfed infant. Use with caution.
- Never take any supplements, including phytoestrogens, if you are pregnant or breastfeeding without first checking with your healthcare provider.
What else should I know about phytoestrogens?
- Phytoestrogens absorbed from food is safe for most people. Phytoestrogen supplements are possibly safe for most adults when taken in recommended doses.
- Check with your healthcare provider before taking any herbal supplement, including phytoestrogens.
- Take phytoestrogens exactly as per label instructions.
- Dietary supplements often contain many ingredients. Check labels for the components in the phytoestrogen product you choose.
- Phytoestrogens are marketed as dietary supplements and are not regulated by the FDA. Products may differ in formulations and strengths, and labels may not always match contents; exercise caution in choosing your product.
- Store safely out of reach of children.
Summary
Phytoestrogens are natural substances that are similar to estrogens, the human female sex hormones. Phytoestrogens are taken to compensate for the drop in estrogen levels in menopausal women and relieve menopausal vasomotor symptoms such as hot flashes and night sweats, and prevent bone loss and brittle bones (osteoporosis). Common side effects of phytoestrogens include allergic reactions, abdominal pain, muscle pain (myalgia), and sleepiness. Do not take phytoestrogens if you are pregnant. Consult your doctor if breastfeeding.
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Treatment & Diagnosis
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- Menopause and Perimenopause, A Woman's Guide to
- Male Menopause
- Premature Menopause
- Perimenopause
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- Male Menopause
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- Menopause Symptoms
- Ask the Experts - Menopause
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Medications & Supplements
- estradiol valerate - injection, Delestrogen
- estradiol, Alora, Climara, Delestrogen, Depo-Estradiol, Divigel, Elestrin, Estrace, and Others
- estrogens cream - vaginal
- esterified estrogens and methyltestosterone, Estratest, Estratest HS
- Side Effects of Premarin Vaginal Cream (conjugated estrogens)
- estrogens conjugated (Premarin)
- Side Effects of Premarin (conjugated estrogens)
- Conjugated Estrogens (Cenestin, Enjuvia, Estrace, and Others)
- Side Effects of Estratest (esterified estrogens and methyltestosterone)
- estrogen/progestin - oral, Activella, Femhrt, Ortho-Prefe
- Side Effects of Prempro (conjugated estrogens/medroxyprogesterone)
- conjugated estrogens vaginal cream (Premarin Vaginal Cream)
- estrogens (synthetic)-vaginal cream
- estrogens conjugated synthetic (Cenestin)
- esterified estrogens (Menest)
- methyltestosterone w/ estrogen - oral, Estratest
- conjugated equine estrogens and medroxyprogesterone acetate, Prempro, Premphase
- Side Effects of Cenestin (conjugated estrogens)
- Side Effects of Menest (esterified estrogens)
Prevention & Wellness

Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
https://reference.medscape.com/drug/isoflavones-daidzein-phytoestrogens-344513
https://www.ncbi.nlm.nih.gov/books/NBK77935/
https://jamanetwork.com/journals/jamainternalmedicine/fullarticle/648139
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6390141/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3074428/
https://www.ncbi.nlm.nih.gov/books/NBK77935/