Health ConditionsHot flashes (HFs) are defined as transient sensations of heat, sweating, flushing, anxiety, and chills lasting for 1–5 minutes, and constitute one of the most common symptoms of menopause among women. More precisely, a hot flash is a rapid and exaggerated heat dissipation response, consisting of profuse sweating, peripheral vasodilation, and feelings of intense, internal heat.
Hot flashes are characterized by sudden strong sensations of fever or sweating on the face, neck, and upper chest area, as well as palpitations, anxiety, irritability, and panic. The maximum increase in temperature occurs in the digits and toes, where temperature may increase from a normal of 20°C to 33°C, though the symptoms of hot flashes are most intense in the upper torso, including the head, neck, and upper chest. Hot flashes often occur at night, interfering with sleep, affecting mental health, and lowering quality of life.
Previous studies have shown that up to 85% of women experience hot flashes. Hot flashes are also a common stressful symptom for individuals with cancer, particularly women with a history of breast cancer and men with prostate cancer. For men, the phenomenon of hot flashes often occurs as a result of medical or surgical treatment for prostate cancer; although up to 75% of men treated with androgen deprivation therapy may experience hot flashes, there are limited therapeutic options for their treatment.
The basis of hot flashes lies in abnormal hypothalamic thermoregulatory control, resulting in an abnormal vasodilatory response to minor elevations of core body temperature. The onset of hot flashes is hypothesized to be related to dysfunction of the thermoregulatory nucleus, which is essential in regulating the homeostatic range and the core body temperature. This nucleus maintains the core body temperature within a homeostatic range termed the thermoregulatory zone.
Recent studies suggest that hot flashes are triggered by small elevations in core body temperature acting within a reduced thermoneutral zone in symptomatic postmenopausal women. This narrowing of the thermoneutral zone may be due to elevated central noradrenergic activation, a contention supported by observations that clonidine and some relaxation procedures ameliorate hot flashes.
Various hormones and neurotransmitters modulate vasomotor symptoms, most importantly estrogen. The thinking is that ovarian estrogen withdrawal is the initial mechanism leading to hot flashes. Although the appearance of hot flashes coincides with estrogen withdrawal, this does not entirely explain the phenomenon, because estrogen levels do not differ between symptomatic and asymptomatic women.
Increasing evidence in rodents indicates that estrogens modulate body temperature in females via the central nervous system. Estrogen receptors are widely detected in the brain, especially in brain regions that maintain temperature and energy homeostasis.
Recent data suggest an important role for calcitonin gene-related peptide, hypothalamic kisspeptin, neurokinin B and dynorphin signal system, serotonin, and norepinephrine in the causation of hot flashes, in addition to estrogen deficiency, which plays a cardinal role.
When estrogen levels drop in menopause, negative feedback is removed, leading to an overactivity of KNDy neurons and an excessive release of Neurokinin B. Elevated NKB is now understood to be a key player in triggering the hot flash response by impacting the thermoregulatory center. Kisspeptin (involved in GnRH release) and Dynorphin (an opioid peptide with inhibitory effects) also contribute to the complex regulation within this neuronal network.
During menopause, when estrogen levels are low, abnormalities in the hypothalamic preoptic area (POA) of the thermoregulatory center can cause hot flashes. Under low estrogen conditions, differentially expressed proteins in the hypothalamus are associated with glutamatergic and GABAergic synapses. The number of glutamatergic neurons in the POA is decreased, while the number of GABAergic neurons is increased. Chemogenetics showed that rat body temperature decreased slowly after glutamatergic neurons were activated and increased quickly after glutamatergic neurons were inhibited, while it increased quickly after GABAergic neurons were activated and decreased slowly after GABAergic neurons were inhibited.
Thermoregulatory and brain activity changes during individual hot flash episodes observed in women with hot flashes suggest that hot flashes are under central nervous system influence. Because hot flashes affect only some women, preexisting neurobiological traits might predispose to their development. Previous studies have implicated the insula during the perception of hot flashes and the hypothalamus in thermoregulatory dysfunction.
Clusters of factors have been identified as associated with hot flashes, including menopausal stage, hormones, race/ethnicity, body mass index (BMI), smoking, alcohol consumption, and physical activity. Cigarette smoking, later menopausal stage, and low estrogen levels have been consistently associated with an increased risk of hot flashes.
Consistent evidence suggests that smoking is associated with an increased risk for hot flashes. There is a significant interaction between cigarette smoking and body mass index (BMI), so that thin women who smoked in the premenopausal period were most likely to experience hot flashes (prevalence ratio 1.9). Several risk factors for menopausal hot flashes were identified, including current and former cigarette smoking. Factors associated with decreased odds of hot flashes included more than five years of cessation of cigarette smoking.
Body mass index and body fat composition have been shown to be associated with both increased and decreased risk of hot flashes in different studies. In perimenopausal women, after controlling for confounders, a BMI ≥25 kg/m² was associated with an odds ratio of 2.00 for hot flashes. The relationship between BMI and hot flashes appears to be complex and non-linear, with evidence varying by menopausal stage and other co-variables.
Duration of hot flashes was associated with race, among other factors. In the final model, only race, alcohol consumption, leisure activity, and menopause status were retained as independent predictors. White women had significantly shorter hot flash durations than non-white women. The association between African-American race and increased likelihood, severity, and frequency of hot flashes can be strong when considered alone.
Anxiety remained a significant risk factor for hot flashes in multivariable analysis, with an increased risk of 5% for each one-point increase in the anxiety score. Higher education levels were protective, with 34% lower risk of hot flashes among women with education beyond high school.
Duration of hot flashes was associated with leisure activity levels, among other factors. Evidence on whether physical activity reduces menopausal symptoms is inconclusive. Earlier studies have suggested physical activity may act as a possible tool for decreasing some menopausal vasomotor symptoms.
Hot flashes are associated with an increased risk of chronic diseases such as obesity, metabolic syndrome, insulin resistance, and non-alcoholic fatty liver. Hot flashes are also associated with increased ambulatory systolic blood pressure.
Phytoestrogens (PEs) are nonsteroidal plant compounds with similar chemical structure to estradiol, and these compounds appear to demonstrate an estrogenic or anti-estrogenic effect depending on the circulating estrogen level. The two main categories of PEs are isoflavones and lignans; soybeans are rich in isoflavones, and lignans can be found in whole grains, legumes, fruits, vegetables, and flaxseed.
Asian women experience much less frequently vasomotor symptoms than women in America or Europe, and increased attention has been paid to different dietary habits, as the Asian diet is rich in phytoestrogens.
Soy (Glycine max) has been a staple food in East Asian cultures, including China, Japan, and Korea, for thousands of years, consumed in the form of tofu, miso, tempeh, edamame, and soy milk. Soy is a staple in many Asian diets and is consumed in greater quantities in Asian countries than in the United States. Its use as a targeted botanical remedy for menopausal symptoms, however, is a more modern extrapolation from epidemiological observations of lower hot flash rates in Asian women rather than a codified traditional practice for this indication specifically.
Soy isoflavone supplements or soy protein may help to reduce the frequency and severity of menopausal hot flashes, but the effect may be small, and research results have been mixed.
A systematic review and meta-analysis conducted according to Cochrane Handbook guidelines evaluated the effects of isoflavones on the frequency, severity, or composite score of hot flashes compared with placebo. From 277 potentially relevant publications, 19 trials were included. Soy isoflavone supplements, derived by extraction or chemical synthesis, were found to be significantly more effective than placebo in reducing the frequency and severity of hot flashes. Additional studies are needed to further address factors such as dose, isoflavone form, baseline hot flash frequency, and treatment duration.
A 2016 systematic review and meta-analysis of 62 studies involving 6,653 women found that specific phytoestrogen supplementations, such as soy isoflavones, were associated with modest reductions in the frequency of hot flashes and vaginal dryness, but no significant reduction in night sweats. However, many of the studies included in the review were of low quality.
Clinical trials show that daidzein and genistein, especially in equol-producing individuals, can reduce vasomotor symptoms such as hot flashes and night sweats. While results across studies vary, consistent findings support their safety and modest efficacy, particularly for women unable or unwilling to use hormone replacement therapy. Pharmacokinetic studies reveal moderate bioavailability and interindividual variability due to gut microbiota metabolism.
Although information on adverse effects is limited, soy extracts appear to be generally safe when taken for short periods of time. However, long-term use of soy extracts has been associated with thickening of the lining of the uterus.
Evidence strength: Moderate, but heterogeneous. Meta-analyses show a statistically significant but often modest effect on hot flash frequency and severity. Effect size is variable and influenced by equol-producer status, dose, and form of isoflavone.
Black cohosh was first used by American Indian or Alaska Native people. Extracts from black cohosh have been used as medicine to treat menopausal symptoms in Europe for over 50 years. It was traditionally used by Native Americans and early colonists to treat a variety of conditions including general malaise, abnormalities in kidney function, malaria, rheumatism, sore throat, and menstrual complaints. In Germany, black cohosh has been approved to treat menstrual period pain, menopausal symptoms, fast heartbeat, nervousness, irritability, sleep problems, noise or ringing in the ears, dizziness, sweating, and depression.
The constituents of black cohosh include triterpene glycosides and polyphenols. Black cohosh was initially believed to have estrogen-like activity and modulate tissue-specific subtypes of the estrogen receptor; more recent investigations suggest that it may have serotonergic activity. Purported estrogenic actions of black cohosh are refuted by current, up-to-date laboratory and clinical studies of commercially available hydroalcoholic extracts. Alternative mechanisms of menopausal symptom relief have been proposed, one of which suggests serotonergic activity by triterpenes to minimize episodes of hot flashes and bone loss.
A 2023 review of 22 studies of products containing black cohosh extracts, alone or in combination with other herbs, found that they were potentially beneficial for overall menopause symptoms. Data on specific symptoms showed improvements in hot flashes but not anxiety or depressive symptoms.
In three studies with placebo-control groups, there was no significant difference in hot flash frequency between the black cohosh group and the placebo group. Observational and open-label studies have shown some benefits of black cohosh on menopausal symptoms in cancer and noncancer populations; however, clinical trials have not consistently confirmed these effects.
The American College of Obstetricians and Gynecologists states that the data does not show that the use of black cohosh is efficacious in treating menopausal symptoms. The North American Menopause Society echoes this position.
While black cohosh has been used safely in research studies that lasted as long as a year and is generally well tolerated, concerns have been raised that it may cause liver damage in some people. Cases of liver damage — some very serious — have been reported in people taking products labeled as black cohosh. These problems are rare, and it is uncertain whether black cohosh was responsible for them.
Evidence strength: Mixed and inconclusive for hot flash frequency specifically. One large 2023 meta-analysis found potential benefit for overall menopausal symptoms, but several placebo-controlled trials found no significant effect. Evidence quality is generally considered low to moderate.
Red clover (Trifolium pratense) has a long history of therapeutic use, primarily noted for its potential benefits in treating various health conditions. Traditional use historically centered on respiratory complaints such as coughs and bronchitis, as well as skin conditions. Its modern application for menopausal symptoms derives from its isoflavone content and parallels the soy isoflavone research pathway rather than from a direct traditional ethnobotanical lineage for this specific indication.
Red clover isoflavones have structural similarities to endogenous 17β-estradiol and exert their biological effects via activating estrogen receptors (ER), with a higher affinity for ER-β compared to ER-α. The herb contains isoflavones, which have estrogen-like properties and are thought to influence conditions such as menopausal hot flashes, but results from studies on their efficacy have been inconsistent.
A meta-analysis of eight trials (ten comparisons) demonstrated a statistically significant reduction in the daily incidence of hot flushes in women receiving red clover compared to those receiving placebo, with a weighted mean difference of −1.73 hot flushes per day (95% CI −3.28 to −0.18; p = 0.0292). The analysis showed substantive differences in comparisons of postmenopausal women with ≥5 hot flashes per day, when the follow-up period was 12 weeks, with an isoflavone dose of ≥80 mg/day, and when the formulations contained a higher proportion of biochanin A.
Studies on the effects of red clover on menopause symptoms such as hot flashes have had inconsistent results. A 2016 systematic review and meta-analysis found that red clover significantly improved vaginal dryness and vaginal atrophy, but showed less therapeutic effect on psychological status, sexual problems, and sleeping disorders. The review concluded that red clover consumption may decrease the frequency of hot flashes, especially in women with severe hot flashes (5 or more per day).
Evidence strength: Preliminary to moderate. The statistically significant effect reported in meta-analyses is modest in absolute terms, and high between-study heterogeneity limits generalizability.
Flaxseed is the richest source of lignans, which constitute one of the three major classes of phytoestrogens. The lignans associated with flaxseed are primarily secoisolariciresinol (SDG), the essential fatty acid alpha-linolenic acid (a biological precursor to omega-3 fatty acids), as well as fiber. Lignans are thought to have estrogen agonist and antagonist effects, as well as antioxidant properties. Flaxseed has been incorporated into human diets for millennia, primarily as a food ingredient; its specific application to menopausal symptoms is a modern research-driven inquiry.
Preliminary data suggested that flaxseed, as a rich source of dietary lignans, might be a potentially effective treatment for hot flashes. A phase III randomized, placebo-controlled trial was conducted to evaluate the efficacy of flaxseed in reducing hot flashes. Postmenopausal women with or without breast cancer were randomly assigned to a flaxseed bar (providing 410 mg of lignans) for 6 weeks versus a placebo bar. The results of this trial do not support the use of 410 mg of lignans for the reduction of hot flashes.
A separate double-blind, placebo-controlled RCT examined daily consumption of bread containing 25 g of flaxseed (46 mg lignans) over 12 consecutive weeks in 38 postmenopausal women. The outcome variables were the daily number of hot flashes, the Kupperman Menopausal Index, and endometrial thickness. This study similarly did not demonstrate superiority over placebo for climacteric symptoms.
Evidence strength: Weak to negative for hot flash reduction specifically. Despite theoretical rationale based on phytoestrogenic mechanisms, adequately powered randomized controlled trials have not confirmed efficacy.
Evening primrose oil has been used in traditional Western herbalism primarily for skin conditions and cyclical breast discomfort. Studies have shown that evening primrose may alleviate the side effects of hot flashes according to a systematic review of Iranian herbal medicines. However, the broader evidence base is not supportive: a recent review of several studies suggested that evening primrose oil was no more beneficial than placebo at reducing symptoms. Evidence strength is considered weak and insufficient to draw firm conclusions.
Valerian root has a long history of use in European and Asian traditional medicine, primarily as a calming agent and sleep aid. Systematic review evidence has identified valerian as among the herbs that may alleviate the side effects of hot flashes. There are some early signs that valerian root may help reduce hot flashes. One study of 68 women demonstrated that those who took valerian capsules three times a day for eight weeks experienced a reduced number of hot flashes. Evidence is preliminary and derived from small trials; more rigorous studies are needed.
A systematic review of 19 RCTs found that anise (Pimpinella anisum) and licorice (Glycyrrhiza glabra) were among the herbs that may alleviate the side effects of hot flashes. Both plants have long histories in Middle Eastern and traditional European herbal medicine. Evidence from this context is preliminary and largely derived from small trials; methodological quality limits interpretation.
The European Menopause and Andropause Society (EMAS) emphasizes the importance of lifestyle. There is growing evidence that lifestyle factors such as diet, physical activity, smoking, and alcohol consumption have a significant impact on health and menopausal symptoms.
A randomized controlled trial tested a low-fat vegan diet with whole soybeans in postmenopausal women. A randomized controlled trial of 84 postmenopausal women studied how a low-fat vegan diet with daily soybeans affects hot flashes. The study suggested that severe hot flashes were reduced by 92% in the group that ate the vegan diet. However, evidence about a soy diet alleviating menopausal symptoms is mixed overall.
A Women's Health Initiative study aimed to determine whether a dietary intervention designed to reduce fat intake and increase intake of fruit, vegetables, and whole grains, combined with weight loss, reduces vasomotor symptoms in postmenopausal women. Results from this large study were complex and did not yield straightforward conclusions about fat reduction alone and hot flash reduction.
Consuming white meat, dairy products, vegetables, and following a Mediterranean diet pattern with proper weight reduce the symptoms of menopause, while excessive consumption of high-protein diets, especially red meat, oil, and salt, increases the risk of osteoporosis as a major complication of menopause. Eating foods such as soy and legumes, adequate calcium intake, omega-3 fatty acids, and vitamins D, E, B2, B1, and C, as well as the consumption of natural antioxidants and regular physical activity, can reduce the effects of menopause, especially hot flashes.
In the case of obesity or overweight, losing just 5 kg of weight improves the tolerability of hot flashes by 30%. Research shows that higher body fat is linked to menopause symptoms like hot flashes and night sweats. A 2023 study found that women who had obesity were more likely to have more severe menopausal symptoms, and also found that lifestyle changes leading to weight loss may help reduce hot flashes.
Some research suggests that moderate alcohol consumption is associated with shorter durations of hot flashes. Women consuming at least 12 alcoholic drinks in the previous year had a significantly shorter duration of hot flashes with a smaller effect of hot flash duration on increasing in time to peak severity compared to those who consumed less. However, these relationships are epidemiological and should be interpreted with caution, as alcohol confers numerous other health risks and findings across studies are inconsistent.
Regular exercise ensures metabolic health and reduces the number and intensity of hot flashes. There is mixed evidence on exercise and hot flashes. Some research suggests that exercise could help reduce this symptom. However, exercise can also sometimes trigger hot flashes in the short term. Smaller trials have reported benefits, such as supervised aerobic and resistance programs that improved thermoregulation and lowered symptom severity.
Increasing physical activity is one alternative to hormone therapy. Evidence on reducing cardiovascular disease by physical activity exists especially among postmenopausal women. However, evidence on whether physical activity reduces menopausal symptoms is still inconclusive.
Confirmed risk factors for menopausal hot flashes include current and former cigarette smoking. Factors associated with decreased odds of hot flashes include more than five years of cessation of cigarette smoking.
Because hot flashes are triggered by core body temperature elevations, procedures to reduce core temperature, such as lowering ambient temperature, are beneficial. Lifestyle modifications are proposed as the first step in the management of less severe hot flashes.
27-Deoxyactein is a key triterpene glycoside and active constituent of black cohosh (Cimicifuga racemosa), the most extensively studied botanical for menopausal hot flashes. Its presence is used to standardize black cohosh extracts studied in multiple RCTs demonstrating reductions in vasomotor symptoms.
8-Prenylnaringenin (8-PN) is the most potent known plant-derived phytoestrogen, derived from hops (Humulus lupulus). It has been specifically studied in RCTs for menopausal hot flashes; a combination trial (soy isoflavones + 8-PN + melatonin) demonstrated improved hot flashes in postmenopausal women, though standalone RCT results are conflicting.
Alfalfa is rich in phytoestrogens (coumestrol, formononetin, biochanin A) that bind estrogen receptors and may mitigate vasomotor symptoms. A study combining alfalfa with sage in 30 menopausal women reported reduced hot flashes. Broader Cochrane evidence on phytoestrogens from multiple plants shows modest hot flash reduction.
Multiple recent randomized, double-blind, placebo-controlled trials have assessed standardized A. racemosus (shatavari) root extract for vasomotor symptoms including hot flashes in perimenopausal and menopausal women, with positive results. The mechanism is attributed to phytoestrogenic activity of steroidal saponins (shatavarins) that bind estrogen receptors.
Epimedium prenylflavonoids act as phytoestrogens binding estrogen receptors, providing a plausible mechanism for alleviating vasomotor symptoms like hot flashes in postmenopausal women. A publication in the Journal of Ethnopharmacology documented icariin's binding to estrogen receptors potentially alleviating menopausal discomfort. The 24-month human bone trial included menopausal women without reporting hyperplasia, suggesting a safe estrogenic profile.
Biochanin A is an isoflavone found in red clover and chickpeas, metabolized in vivo to genistein. As a key constituent of red clover isoflavone preparations validated in meta-analysis (statistically significant −1.73 hot flushes/day), it contributes to the documented phytoestrogenic activity relevant to hot flash reduction.
Black cohosh (Cimicifuga racemosa) is the most extensively studied botanical for menopausal hot flashes. Multiple RCTs are documented in the NIH ODS fact sheet; it appears to act via serotonergic rather than estrogenic pathways. Evidence is mixed across trials but overall supports modest reductions in hot flash frequency and severity.
B. falcatum has been traditionally used for menopausal symptoms including hot flashes in East Asia. In a clinical trial, a decoction with B. falcatum as a major ingredient showed efficacy for relieving vasomotor symptoms in postmenopausal women. In vivo studies also confirm potent hypothermic effects.
At least two RCTs have tested Vitex specifically for hot flashes in peri- and postmenopausal women, with one finding significant reductions in frequency and severity versus placebo. A combination trial with St. John's wort found no significant difference from placebo. Evidence is mixed and the herb's phytoestrogenic and dopaminergic mechanisms provide partial mechanistic rationale.
Daidzein is a soy isoflavone metabolized to the more potent equol by gut flora in some individuals. Clinical trials, particularly in equol-producers, show reduction in vasomotor symptoms including hot flashes. Evidence is modest and population-dependent based on individual microbiome composition.
Clinical trials of soy isoflavones including daidzin-containing preparations have shown modest reductions in hot flash frequency in menopausal women, especially in equol-producing individuals. The Cochrane review found inconsistent overall evidence, while some individual RCTs demonstrated significant benefit.
A small clinical study (Yakoot et al., 2011) found that a herbal formula containing damiana improved menopausal symptoms including vasomotor symptoms. MSKCC acknowledges this evidence while noting confirmatory research is needed. Damiana's phytoestrogenic and anti-aromatase properties provide biological plausibility.
DHEA has been studied for vasomotor symptoms including hot flashes in postmenopausal women. Evidence is limited and inconsistent; oral DHEA is generally not considered effective enough to treat bothersome vasomotor symptoms as a standalone therapy. A Cochrane review found only uncertain evidence that DHEA decreases menopausal symptoms including hot flashes.
Evening primrose oil (EPO) contains gamma-linolenic acid (GLA) and has been used for menopausal hot flashes. A 2018 RCT showed EPO reduced hot flash severity; a 2021 RCT found it reduced night sweat frequency and severity but not hot flash frequency. Evidence is mixed but the ingredient is consistently studied and used for this indication.
Fennel-containing preparations have been tested in human RCTs for menopausal hot flashes. A fennel-valerian combination showed significantly reduced hot flash frequency and severity vs. placebo at 1–2 months. A standalone fennel RCT showed no significant difference over placebo, attributed to a high placebo response.
Standardized fenugreek seed extract has demonstrated significant reductions in hot flash frequency in menopausal women in multiple RCTs. One 90-day RCT with 1,000 mg/day reported a 47.8% decrease in hot flashes, with 32% of fenugreek-group women reporting complete resolution. The effect is attributed to fenugreek's phytoestrogenic activity increasing circulating estradiol.
Flaxseed is a rich source of the dietary lignan secoisolariciresinol diglucoside (SDG), metabolized to enterolignans with weak phytoestrogenic activity. Clinical trials for menopausal hot flashes show mixed results—smaller studies demonstrate benefit while a phase III NCCTG RCT did not confirm significant efficacy at 410 mg lignans/day.
Formononetin is a methoxylated isoflavone found primarily in red clover, serving as a metabolic precursor to daidzein. As a major constituent of red clover isoflavone preparations that have demonstrated statistically significant hot flash reductions in meta-analysis (−1.73/day vs. placebo), it contributes to the phytoestrogenic activity of clinically validated red clover extracts.
Japanese clinical trials beginning in the early 1960s demonstrated gamma oryzanol reduces hot flashes in menopausal and surgically postmenopausal women. In one study of 21 women given 300 mg/day for 38 days, more than 67% experienced a 50% or greater reduction in symptoms. The proposed mechanism involves suppression of LH secretion by the pituitary and stimulation of hypothalamic endorphin release.
Genistein is the predominant soy isoflavone and has the strongest individual clinical evidence for menopausal hot flashes. A 2-year double-blind RCT (n=389) showed a 56.4% reduction in mean hot flush frequency after 12 months of 54 mg/day genistein without adverse endometrial effects. Evidence is among the strongest for any single phytoestrogen.
A 2022 systematic review of 15 placebo-controlled RCTs found ginseng significantly reduced hot flash scores (SMD: −0.34, 95% CI: −0.66 to −0.01) and overall menopausal symptom burden in postmenopausal women. However, effects on hot flash frequency specifically, hormone levels, and endometrial thickness were not consistently demonstrated. Evidence quality is rated low to moderate due to risk of bias in the included studies.
GLA (via evening primrose oil) has been tested in multiple RCTs for menopausal hot flashes with some evidence of benefit. A randomized double-blind trial (n=56 menopausal women, BMJ 1994) found gamolenic acid from EPO significantly reduced daytime hot flush frequency. Subsequent trials and systematic review data support a modest but real effect on hot flush severity and frequency.
Soy isoflavones including glycitein reduce vasomotor symptoms (hot flashes) in menopausal women by acting as phytoestrogens at hypothalamic estrogen receptors. Meta-analytic evidence confirms that soy isoflavones improve hot flash frequency and severity in postmenopausal women. Glycitin is a constituent of the isoflavone preparations used in these trials.
A single-blind, parallel, dose-comparison human study in 22 postmenopausal women found that HMRlignan at 72 mg/day for 8 weeks reduced mean weekly hot flash frequency by 50% in the high-dose group. ENL levels increased substantially from baseline alongside this symptomatic improvement. No significant safety concerns were identified.
A single-blind, parallel, dose-comparison RCT in 22 postmenopausal women (36 mg/d or 72 mg/d for 8 weeks) showed statistically significant reductions in hot flash frequency, particularly at the higher dose. The higher dose produced roughly a 55% reduction in hot flashes at 4 weeks and a sustained ~50% reduction at 8 weeks. HMRlignan is rapidly absorbed and converted to enterolactone, a phytoestrogen that modulates estrogen receptor activity, providing a plausible mechanism.
Hops contains 8-prenylnaringenin (8-PN), considered the most potent phytoestrogen yet identified, which binds estrogen receptor-alpha. Multiple RCTs have tested standardized hop extracts for vasomotor symptom relief in menopausal women, with a 100 µg/day dose of 8-PN showing superiority to placebo at 6 weeks. Effects are modest and not always sustained at 12 weeks.
Isoflavones are a class of phytoestrogens (including genistein, daidzein, formononetin, biochanin A) found in soy, red clover, and kudzu, extensively studied in RCTs for menopausal hot flashes. Multiple systematic reviews support modest but statistically significant reductions in hot flash frequency, with efficacy modulated by individual equol-producer status.
Kudzu (Pueraria lobata) root is rich in isoflavones including puerarin, daidzin, and daidzein, with established phytoestrogenic activity. Memorial Sloan Kettering cites human evidence for hot flash and night sweat benefit attributed to its isoflavone content. An RCT of kudzu flower extract versus placebo was conducted in menopausal women.
A double-blind placebo-controlled RCT in 90 menopausal women found that 330 mg licorice extract three times daily for 8 weeks significantly reduced both the frequency and severity of hot flashes compared to placebo. Phytoestrogenic compounds in licorice are the proposed mechanism. This is one of the strongest single-herb clinical trials for a menopausal symptom.
Evidence for lignans in reducing hot flashes is mixed. Some earlier studies using flaxseed (21 mg lignans via 40 g/day) found efficacy comparable to conjugated estrogen for mild menopausal symptoms. However, a Phase III RCT (Mayo Clinic, NCCTG N08C7) using 410 mg lignans/day in postmenopausal women found no significant reduction versus placebo. A 2025 review found flaxseed lignans reduced perimenopausal symptoms overall.
Maca (Lepidium meyenii/peruvianum) is a Peruvian Andean root with long traditional use for reproductive and menopausal health. Multiple double-blind RCTs demonstrate significant reductions in vasomotor symptoms including hot flashes in peri- and postmenopausal women through non-estrogenic hormonal mechanisms.
A clinical study in 180 menopausal women found that a supplement containing magnolia bark, soy isoflavones, and lactobacilli more effectively reduced hot flash severity and frequency than the comparator. The 634-woman multicenter RCT found both control and magnolia-containing supplement groups experienced relief from vasomotor symptoms including hot flashes, though magnolia specifically enhanced psycho-affective rather than vasomotor outcomes.
Melatonin has been evaluated in clinical trials for menopausal hot flashes via GABAergic and thermoregulatory mechanisms. One double-blind RCT found 3 mg melatonin produced significant improvement in vasomotor symptoms in women with severe climacteric symptoms. A combination RCT (soy isoflavones + 8-prenylnaringenin + melatonin) also demonstrated improved hot flashes. Evidence is preliminary.
Gamma-oryzanol (γ-oryzanol), derived from Oryza sativa bran oil, has been used in Japan since the 1960s for menopausal hot flashes and is approved there for this indication. Multiple clinical studies show 67–85% of women experienced significant symptom reduction at 300 mg/day.
A randomized clinical trial (Fahami et al., 2010; PMC3203277) compared passionflower to St. John's wort in 59 menopausal women over six weeks. Both groups showed significant decreases in menopausal symptoms—including hot flashes, night sweats, insomnia, depression, and headaches—at weeks three and six (p<0.05). The proposed mechanism involves passionflower's GABAergic activity reducing central nervous system hyperexcitability associated with estrogen withdrawal, as menopause-related symptoms are partly linked to low GABA tone.
Paeonia lactiflora extract has demonstrated effects on menopausal hot flashes in animal models, acting on the hypothalamic-pituitary-gonadal axis, serotonergic pathways, and neuropeptide signaling. Clinical reviews suggest Chinese herbal formulas containing white peony have comparable effects to hormone therapy for menopause symptoms.
Phytoestrogens are a broad class of plant-derived compounds (isoflavones, lignans, coumestans) binding estrogen receptors, and are among the most studied non-hormonal approaches to menopausal hot flashes. Cochrane reviews and multiple systematic analyses confirm modest but statistically significant reductions in hot flash frequency versus placebo across multiple subclasses.
Progesterone alone or in combination with estrogen reduces vasomotor symptoms (hot flashes, night sweats) in perimenopausal and postmenopausal women. A PubMed-indexed RCT and clinical trial data confirm oral micronized progesterone cyclically given in perimenopause decreases hot flashes and improves associated sleep disruption.
Pycnogenol (French maritime pine bark extract) has been studied in multiple RCTs for menopausal symptoms including hot flashes. A double-blind RCT in 200 peri-menopausal women and a second trial in 38 women both demonstrated significant reductions in hot flash severity. Mechanism is non-hormonal, involving vascular relaxation via nitric oxide pathways.
Red clover (Trifolium pratense) isoflavones have been evaluated in multiple RCTs for menopausal hot flashes. A 2021 systematic review and meta-analysis of 8 trials found a statistically significant reduction of approximately 1.73 hot flashes per day versus placebo. Individual RCTs show reductions in hot flush frequency from the first month of supplementation.
Small human RCTs indicate resveratrol may reduce hot flash frequency and severity in perimenopausal and menopausal women through phytoestrogenic and vasodilatory mechanisms. A pilot randomized, placebo-controlled study in 80 perimenopausal women found 150 mg/day for 12 weeks reduced hot flash frequency by approximately 30% versus placebo. Evidence is preliminary due to small sample sizes.
The Rheum rhaponticum root extract ERr 731 has been tested in multiple RCTs and a 2-year clinical study for reduction of menopausal vasomotor symptoms including hot flashes. A 12-week double-blind RCT in 112 perimenopausal women showed significant reduction in hot flash frequency and severity versus placebo.
A 2019 RCT (Complementary Therapies in Clinical Practice) and an observational study (2024, Nutrients) both reported reductions in hot flash frequency and intensity with RJ supplementation in peri- and postmenopausal women. Phytoestrogenic activity of RJ provides a mechanistic rationale.
Sage (Salvia officinalis) has been evaluated in multiple clinical trials and a 2023 systematic review/meta-analysis, which found Salvia officinalis significantly reduces hot flash frequency in postmenopausal women. Traditional use in European folk medicine for hot flashes is also well-documented.
A 2016 randomized, double-blind, placebo-controlled trial (n=36 women aged 40–70) found that schisandra extract (BMO-30, ~392 mg/day) significantly reduced hot flashes, sweating, and palpitations versus placebo over 6 weeks, with continued improvement at 12 weeks (Kupperman Index and Menopause Rating Scale). A supportive mouse study using VCD-induced ovarian failure also demonstrated reduced tail skin temperature with schisandra treatment.
Secoisolariciresinol diglucoside (SDG) is the principal phytoestrogenic lignan of flaxseed, converted by gut bacteria to enterodiol and enterolactone. It has been directly studied in phase III RCTs for menopausal hot flashes. While a large NCCTG trial at 410 mg/day SDG did not show significant benefit versus placebo, smaller studies support its traditional phytoestrogenic use.
Sesame lignans are converted to enterolactone, a weak phytoestrogen that may reduce hot flash frequency by modulating thermoregulatory centers via estrogen receptor binding. The clinical study in 24 postmenopausal women using 50 mg sesame powder showed hormone status improvement, consistent with vasomotor symptom relevance. Evidence is preliminary and largely mechanism-based rather than from dedicated hot flash RCTs.
Multiple RCTs and meta-analyses demonstrate that soy isoflavones (genistein, daidzein) significantly reduce the frequency and severity of hot flashes in menopausal and perimenopausal women. A 2012 meta-analysis of 19 RCTs found isoflavones reduced hot flash frequency and severity by ~26% vs. placebo. Effects are real but modest compared to estradiol.
Soy isoflavones (primarily genistein and daidzein) have been studied in numerous RCTs for menopausal hot flashes with mixed but partially positive results. Several systematic reviews support modest efficacy, particularly in equol-producing individuals and those with higher baseline hot flash frequency. Classified as scientifically studied though not universally efficacious.
A systematic review and meta-analysis of 17–19 RCTs found soy isoflavones significantly reduced hot flash frequency by approximately 20% and severity by approximately 26% compared with placebo. Asian postmenopausal women, who consume substantially more dietary soy, have a markedly lower incidence of hot flashes than Western women. Evidence is clinically meaningful but effect sizes are moderate and heterogeneity across trials is high.
Multiple clinical studies, including a randomized double-blind placebo-controlled trial of 100 women, found SJW significantly reduced hot flash frequency, duration, and severity versus placebo by 8 weeks. NCCIH and Mayo Clinic acknowledge this as a small but consistent evidence base.
Ammonium succinate–based dietary supplements have been tested in multiple randomized, double-blind, placebo-controlled trials in perimenopausal and postmenopausal women and significantly reduced hot flushes. A pooled analysis of two RCTs (n=227) found significant alleviation of 16 of 21 menopausal symptoms on the Greene Climacteric Scale. Estradiol levels also increased significantly.
Valerian root (Valeriana officinalis) contains phytoestrogenic compounds and has been evaluated in a double-blind RCT of 68 menopausal women, showing significant reductions in hot flash severity and frequency versus placebo over 8 weeks. Evidence is preliminary but originates from a controlled clinical trial.
Multiple RCTs have tested vitamin E for menopausal vasomotor symptoms. A Mayo Clinic placebo-controlled crossover trial found vitamin E (800 IU/day) reduced hot flashes by approximately one per day versus placebo—statistically significant but clinically modest. A separate RCT in postmenopausal women found vitamin E (200 IU twice daily for 8 weeks) reduced hot flash frequency by roughly one-third.
Vitex agnus-castus (chaste tree) has been evaluated in RCTs for menopausal vasomotor symptoms including hot flashes. A 2025 systematic review confirms evidence from clinical studies that it modulates dopaminergic, phytoestrogenic, and serotonergic pathways; RCTs show improvements in hot flashes and vasomotor symptoms versus placebo.
Wild yam's diosgenin is a phytoestrogen that interacts weakly with estrogen receptors, forming the basis for its use against menopausal hot flashes. The only rigorous human trial — a double-blind, placebo-controlled crossover study of 23 menopausal women (Komesaroff et al., Climacteric 2001) — found no statistically significant reduction in hot flash frequency or severity versus placebo. Evidence is therefore scientific in design but negative in outcome; human benefit is unproven.
Anemarrhena is a key ingredient in the classic TCM formula Zhi Bai Di Huang Wan, prescribed for menopausal hot flashes and night sweats. It is traditionally understood to 'nourish Yin and clear empty heat,' the TCM mechanism underlying hot flashes. Well-documented traditional use across multiple centuries of East Asian clinical practice.
Borage oil is traditionally and widely used by women for hot flash reduction, attributed to GLA's prostaglandin-modulating effects. Clinical RCT evidence using the closely related GLA source evening primrose oil found no benefit over placebo for hot flash frequency or severity. No borage-oil-specific RCT for hot flashes exists in peer-reviewed literature.
DIM is widely used by practitioners and consumers to alleviate menopausal hot flashes on the basis that it favorably shifts estrogen metabolism. No published RCT has used hot flash frequency or severity as a primary endpoint for DIM specifically. The use is extrapolated from DIM's known effects on estrogen metabolite ratios.
Wild yam (Dioscorea villosa) is widely used in traditional and alternative medicine for menopausal hot flashes, leveraging its phytoestrogenic diosgenin content. However, the best-available clinical evidence—a double-blind, placebo-controlled trial in 23 post-menopausal women—found no significant reduction in hot flashes versus placebo.
Dong quai (Angelica sinensis) has been used for over 2,000 years in Traditional Chinese Medicine for menopausal complaints including hot flashes, typically in multi-herb formulas. Controlled clinical trials of dong quai used alone have not demonstrated significant hot flash improvement, placing evidence primarily in the traditional category.
Dong quai root (Angelica sinensis root) is the same medicinal material as Dong Quai—used for millennia in TCM in combination formulas for menopausal complaints including hot flashes. Solo-use RCTs have not demonstrated significant hot flash reduction, placing evidence in the traditional-use category.
Kava is used in herbal medicine for hot flashes associated with perimenopause, leveraging its anxiolytic and neurovegetative-stabilizing properties. Clinical trials in perimenopausal women demonstrated improvement in mood, anxiety, and general climacteric complaints, but hot flash frequency and severity were not significantly reduced as primary endpoints. The specific hot flash indication therefore rests on traditional herbal practice rather than direct clinical proof.
Motherwort has a long traditional use for menopausal hot flashes, particularly those accompanied by nervous tension and palpitations. The EMA mentions it for menopausal symptoms, and traditional European herbalism consistently recommends it for this indication. No dedicated clinical trials confirm efficacy specifically for hot flashes.
Pregnenolone is used traditionally as a precursor-hormone supplement for menopausal hot flashes, based on its ability to support downstream estrogen and progesterone production. Specific controlled clinical trial evidence for pregnenolone reducing hot flashes is lacking; the relationship is primarily mechanistic and traditional-practitioner-based.
Hot flashes are a core indication in TCM for Rehmannia, classified as heat manifestations of Yin deficiency. Prepared Rehmannia (Shu Di Huang) and raw Rehmannia are both used in classical menopausal formulas such as Zhi Bai Di Huang Wan and Er Xian Tang. TCM clinical practice over centuries has consistently applied Rehmannia to night sweats and hot flashes associated with kidney Yin deficiency.
Rehmannia is used traditionally and in formulated TCM preparations for menopausal hot flashes and night sweats. Catalpol may stimulate adrenal cortical hormones, offering a biological basis. A few studies confirm effectiveness in reducing night sweats and hormone disruptions when rehmannia is taken as part of multi-herb formulas.
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