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ERr 731, black cohosh, shatavari, and gamma-oryzanol are four hot flash supplements backed by human clinical evidence. These ingredients intervene at different points along the temperature control pathway, from estrogen signaling in the hypothalamus to the autonomic surge that produces flushing and sweating.*
A hot flash happens when hormonal changes shrink the brain’s comfortable temperature range — the thermoneutral zone — so much that a tiny rise in core temperature triggers a full heat dump.
The collapse of the thermoneutral zone comes from three things going awry:
Estrogen signaling into the thermostat weakens.
The brain circuits that interpret that signal become jumpy and unstable.
The autonomic nervous system overreacts, launching the flushing and sweating of a hot flash.
The best hot flash supplements target each of the layers in that cascade: reinforcing estrogen signaling, stabilizing the brain circuits that regulate temperature, and modulating the sympathetic nervous system response that produces flushing and sweating [1].*
In this article, we’ll examine four hot flash supplements with human clinical evidence — including how each works, what clinical trials found, and where each fits into the brain’s temperature control pathway.*
What Are Hot Flashes?
Hot flashes are sudden, brief periods of sensations of intense heat, which are caused by alterations in the brain’s temperature‑regulation system during the menopausal transition. Most last about 1–5 minutes. Along with night sweats, they're classified as vasomotor symptoms (VMS).
They are one of the hallmark perimenopause symptoms, affecting ~85% of women during the transition. And although each individual hot flash is transient, episodes often recur for years.
The Study of Women's Health Across the Nation (SWAN) — the largest and longest running longitudinal study of the menopausal transition in US women — found that hot flashes lasted a median of 7.4 years across the menopausal transition.
That’s a brutally long horizon for a momentary event. Which is why hot flash relief is table stakes for the best perimenopause supplements.*
Comparing Hot Flash Supplements: Mechanism and Evidence
What Is ERr 731 And Does It Help With Hot Flashes?
ERr 731 is a standardized extract of rhapontic rhubarb (Rheum rhaponticum) with clinical evidence for relieving hot flashes during perimenopause. In a randomized placebo-controlled trial, ERr 731 reduced hot flashes from about 12 to fewer than 3 per day after 12 weeks, while the placebo group remained near baseline.*
ERr 731 is a standardized extract of rhapontic rhubarb. Not the kind of rhubarb people bake into pies. It's a different species, with kind of a weird backstory [4].
For centuries, medicinal rhubarb was one of Europe's most coveted and most expensive imports, shipped from China as a prized remedy. When European botanists finally bred their own version as a cheap substitute — Rheum rhaponticum — it proved to be a sad disappointment, lacking the compounds that gave true medicinal rhubarb its punch [5].
But this "failed" rhubarb contained something that wound up being far better.
Rheum rhaponticum is rich in hydroxystilbenes, polyphenols that are structurally related to resveratrol [6].
Chemical structure of rhaponticin, a hydroxystilbene and major constituent of ERr 731. From V.P. Dubey, V.P. Sureja, D.B. Kheni, J. Biomed. Res. 38 (2024) 278–286. Licensed under CC BY 4.0.
These polyphenols bind to estrogen receptors, specifically ERβ. In fact, ERr 731's hydroxystilbenes have been shown to activate ERβ at levels comparable to natural estrogen, while showing no detectable activation of ERα [4].
ERβ is densely expressed in the preoptic area of the hypothalamus, the region that houses the neurons that set the thermoneutral zone [7]. By selectively stimulating ERβ there, ERr 731 helps to restore some of that estrogen‑dependent upstream signaling that narrows as ovarian estrogen declines.*
The strongest evidence for ERr 731 in hot flashes comes from a randomized trial in perimenopausal women who started out pretty deep in the miserable end of the vasomotor symptom spectrum. Twelve hot flashes a day, every day.
One group got ERr 731, the other got placebo.
At week 12, the placebo group was basically still stuck at baseline, going from 12.1 hot flashes to 11.4. Not great.
Meanwhile, the group on ERr 731 was averaging just 2.8 per day, with nearly 4 in 5 (78.6%) reporting major improvement [8].
The supplement's benefits seem to have staying power, too.
In an open-label follow-up over almost two years, women who improved continued to respond to ERr 731, and nothing scary showed up on the safety side [9].
So ERr 731 is essentially stepping in for estrogen at the top of the chain. But estrogen signaling is only one piece of the hot flash circuit. *
Can Black Cohosh Reduce Hot Flashes and Night Sweats?
Black cohosh has clinical evidence for reducing vasomotor symptoms, including hot flashes and night sweats. In a large analysis of randomized trials, black cohosh reduced hot flash frequency by about 60% versus placebo. It appears to act on serotonin signaling in the hypothalamus, regulating the neural circuitry that determines when the body triggers a hot flash.*
Black cohosh comes from Actaea racemosa, a woodland plant native to North America. If you've ever gone hiking in the eastern US, there's a decent chance you've brushed past it.
Above ground, Actaea racemosa is an elegant wildflower, crowned with tall spikes of white flowers. The business end of black cohosh is buried underground. That tangled mass of knotted rhizomes and roots is what winds up in a supplement capsule [10].
It has been used for decades in Europe for hot flash relief, where it has accumulated an impressive track record [11].
In a large comparative analysis pooling 47 randomized trials, black cohosh for hot flashes came out on top as the best‑performing non‑hormonal option. In that dataset, it cut hot flash frequency by about 60% versus placebo [12].
Yet how exactly it pulls this off has been an ongoing scientific mystery.
For a long time, it was assumed that black cohosh worked by mimicking estrogen, not unlike ERr 731. But when scientists removed the ovaries of female rats — essentially throwing them into menopause — and then gave them black cohosh, their estrogen levels stayed flat.
To figure out what receptors it actually was activating, the same research team took black cohosh extract and ran it through a screen, testing it against potential molecular docking sites [13].
Black cohosh locked strongly on 5-HT₇ and 5-HT₁ₐ receptors. Both of which are serotonin receptors.
That might sound kind of strange, but these serotonin receptors are actually concentrated in the preoptic area of the hypothalamus. Serotonergic signaling is a key modulator of the thermoregulatory setpoint, and estrogen normally helps sustain healthy serotonergic tone. It is thought that 5-HT7 activation helps dampen the hyper-responsive firing of the thermoregulatory network that develops after estrogen withdrawal [14].*
So black cohosh is doing its work further downstream, in the neural circuitry that decides when to fire off a hot flash.*
How Does Gamma-Oryzanol Support Hot Flash Relief?
Gamma-oryzanol supports hot flash relief by regulating the autonomic nervous system — the final step in the brain’s temperature-control pathway that triggers flushing and sweating. In an open-label clinical study, 85% of women taking gamma-oryzanol experienced improvements in perimenopause symptoms after 4–8 weeks.*
Flash back to Japan in the 1950s. Post‑war Japan had every reason to turn homegrown raw materials into medicine instead of depending on imported Western drugs. So local scientists began systematically screening indigenous natural products. They started with the one thing that Japan already had mountains of: rice bran [15].
In 1954, researchers isolated a crystalline compound from rice bran oil and dubbed it oryzanol, after the botanical name for rice. Within a decade, gamma-oryzanol emerged as a remedy for menopausal complaints in Japan — especially hot flashes [16].
Modern clinical evidence for gamma-oryzanol is pretty sparse but consistent. In an open-label study of Japanese women, ~85% reported improvements in flushing and sweating [17].
At the same time, serum lipid peroxides (a marker of oxidative stress) fell. That parallel drop should be a clue as to how gamma-oryzanol might be working.
You see, gamma-oryzanol wasn't originally identified as a menopause remedy. It was first characterized as an autonomic regulator, with its action localized to the hypothalamus [18].
A hot flash is, at its core, an autonomic event. The sudden flushing, sweating, and heart palpitations are all outputs of the autonomic nervous system, launched by the hypothalamus when the brain's thermostat misfires.
During the menopausal transition, that thermostat is under heavy fire.
The hypothalamus is vulnerable to oxidative stress, with estrogen rendering some antioxidant support. As estrogen gets unstable, hypothalamic neurons are exposed to more oxidative damage, which pushes them into a hyper-excitable, hair-trigger state [19].
Animal research has shown that gamma-oryzanol crosses the blood–brain barrier intact, and distributes in the brain [20, 21].
Once there, its ferulic acid component may act as a local antioxidant, supporting the redox environment of hypothalamic neurons and helping to quiet the excess firing that would otherwise spill out as inappropriate autonomic discharge — i.e., hot flashes.*
Does Shatavari Help With Menopausal Hot Flashes?
Shatavari helps reduce menopausal hot flashes by supporting estrogen signaling involved in temperature regulation. In a randomized placebo-controlled trial in perimenopausal women, standardized shatavari extract reduced hot flash scores by ~40% after four months. Shatavari’s steroidal saponins activate ERβ, targeting the upstream hormonal signal that helps keep the brain’s thermostat properly calibrated.*
Shatavari (Asparagus racemosus) is a climbing plant native to India.
The name is usually translated as something like, "she who possesses a hundred husbands," which is pretty on-brand for a plant that is supposed to keep you performing through hormonal chaos [22].
For millennia, practitioners of Ayurveda have relied on its root as a tonic for women's health [23].
Only recently has modern biology started to map how it really works.
Shatavari benefits for women emerge from steroid chemistry. Its root is packed with steroidal saponins known as shatavarins [24]. Chemically, they carry a 27‑carbon backbone that looks a lot like the scaffolding of human sex hormones — close enough that estrogen receptors recognize it and respond. Even better, shatavarins appear to bind preferentially to ERβ, the receptor system most relevant to temperature regulation in the hypothalamus [25].*
In recent years, human trials have started putting those biochemical attributes to the test for perimenopause symptoms.
In a randomized, placebo‑controlled trial in 75 perimenopausal women, four months of standardized shatavari extract made a serious dent in hot flashes. Compared to placebo, hot flash scores dropped dose-dependently — by ~40% in response to the 100 mg dose and 28% at 50 mg [26].
By activating ERβ in the hypothalamus, shatavari helps backfill the estrogen‑dependent signaling that normally keeps the brain’s thermostat from overreacting as ovarian estrogen drops.*
Frequently Asked Questions
How long do perimenopause hot flashes last?
Perimenopause hot flashes can last for years, with a median duration of 7.4 years across the menopausal transition. How long they persist depends a lot on when they started.
In the Study of Women’s Health Across the Nation (SWAN), which followed 1,449 women for almost 20 years, women whose hot flashes began after menopause experienced them for a median of 3.4 years.
In contrast, women whose symptoms began in premenopause or early perimenopause experienced them for a median of nearly 12 years, often continuing for more than 9 years after their final period [3].
In other words, the earlier hot flashes start in the transition, the longer they tend to last.
Is black cohosh safe for hot flashes?
Black cohosh is generally considered safe for most women when taken at recommended doses. Clinical studies have followed women for up to one year without identifying major safety issues [27].*
Safety concerns about potential liver injury arose from early case reports in the 2000s. But a meta-analysis of five randomized controlled trials involving 1117 women found no evidence that standardized black cohosh extract affected liver function [28].
And subsequent structured reviews found that most of the early cases had confounding factors — including products where the plant material could not be verified as authentic Actaea racemosa [29]. That’s why modern clinical guidance emphasizes using standardized extracts of authentic Actaea racemosa rather than unverified preparations.*
As with any new supplement, talking with your healthcare provider before starting black cohosh is a good idea.*
What's the difference between hot flashes and night sweats?
Hot flashes and night sweats are the same type of vasomotor symptom. The main difference is when they occur.
During waking hours, hot flashes typically begin with a sudden wave of heat across the chest, neck, and face, followed by flushing and sweating. Most last 1–5 minutes.
Night sweats are hot flashes that occur during sleep. Because you’re under bedding, sweating is often more intense and disruptive.
Both are driven by a narrowed thermoneutral zone in the hypothalamus, the brain region that regulates body temperature.
How long does it take for hot flash supplements to work?
Most hot flash supplements should be used consistently for 8–12 weeks before judging their full effect on perimenopause symptoms. Some women may notice improvements within the first few weeks, but studies show that benefits continue to develop over two to three months [8, 30]. The exact timeline varies by ingredient and individual response.
*These statements have not been evaluated by the Food and Drug Administration. These products are not intended to diagnose, treat, cure or prevent any disease.
