Supplements and menopause: which ones actually work?

The "menopause" aisle in pharmacies has filled up in a few years: black cohosh capsules, isoflavone tablets, evening primrose oil capsules, "hot flash special" blends. The promise is attractive: relieving symptoms without going through hormone therapy. But what are these products really worth? This article sorts through them, without demonizing or overselling: what research shows, what it does not yet show, and what the official position of the learned societies says.

A huge market, light regulation

Before going into the detail of each plant, a point of context is needed. In the United States, the law that governs food supplements (the Dietary Supplement Health and Education Act) does not require manufacturers to prove the effectiveness or even the safety of their product before selling it. It is the opposite of a medicine: the health authority can step in afterwards if a problem is reported, but it approves nothing beforehand. A company can therefore, in many cases, put a product on the market without even informing the health agency¹. In concrete terms, this means that two boxes of "black cohosh 40 mg" bought in two different chains can contain genuinely very different amounts of the active compound studied in the clinical trials. Keep this reservation in mind for everything that follows: the studies test a precise standardized extract, not "the brand you have in your cupboard".

In France, the principle is the same, with a different vocabulary. A food supplement is not authorized before it is sold: it is simply declared by its manufacturer before being placed on the market, through the Compl'alim online procedure, for which the Ministry of Agriculture has been responsible since January 1, 2024. No agency checks beforehand that it is effective, or that it does contain what the label announces. The safety net comes afterwards: it is the Anses nutrivigilance scheme, which collects adverse effects reported by health professionals and by members of the public, and which has already led the agency to advise against certain plants for certain groups. If you experience an adverse effect after taking a supplement, that report is useful: it is what feeds the system.

Soy isoflavones: the best documented supplement

Isoflavones (genistein, daidzein) are plant molecules that bind weakly to the body's estrogen receptors. It is the best studied "natural" supplement for hot flashes, with nearly twenty randomized trials brought together in a reference meta-analysis. The result: compared with a placebo, taking extracted or synthesized isoflavones, for 6 weeks to 12 months, reduces the frequency of hot flashes by about 21% and their severity by about 26%². This is not a disappearance of symptoms, but a statistically clear effect, greater than what is seen with many other "natural" products. The same analysis notes that doses providing more than 18.8 mg of genistein were twice as effective as lower doses, which points to a genuine dose-response relationship rather than a simple placebo effect.

Two official reference points frame their use in France and in Europe, and they are often missing from the boxes. On the one hand, Afssa (now Anses), in its March 2005 report on phytoestrogens, holds that an intake of 1 mg of aglycone isoflavones per kilogram of body weight per day presents no particular risk, that is about 60 mg per day for a woman of 60 kg, and recommends that supplements carry the statement "Not advised for women with a personal or family history of breast cancer". The report also calls for caution in people treated for hypothyroidism. On the other hand, the 2015 EFSA opinion on isolated isoflavones did not identify an adverse effect on the breast, the endometrium or the thyroid at the doses and durations studied, but specifies that its conclusions apply only to postmenopausal women without current or past hormone-dependent breast or uterine cancer.

This subject remains debated (see below the position of The Menopause Society, formerly NAMS), notably because the effect varies a great deal from one woman to another, partly according to the ability of her gut microbiome to turn daidzein into equol, a more active metabolite. It is therefore not a universal "yes", but one of the most solid files in the aisle.

Black cohosh: results, but an official warning

Black cohosh (Cimicifuga racemosa) is probably the best-selling menopause supplement in North America. A meta-analysis bringing together nine randomized placebo-controlled trials showed that, among the six trials where a significant effect was observed, the improvement in vasomotor symptoms reached about 26%³. The honest caveat is that heterogeneity between studies was substantial: some trials show no difference from placebo, probably because of very variable preparations, doses and treatment durations.

The other question, frequently raised, concerns liver safety. A case series reported liver injury in users of black cohosh. But when a team re-assessed nine of these suspected cases with a rigorous method of causality assessment, the responsibility of the plant could not be excluded or was judged unlikely in eight cases out of nine; in the ninth, causality remained only "possible", with a preparation of unknown brand and an unspecified dosage⁴. In other words: the signal exists and justifies caution, but it is far from being as clear-cut as its reputation suggests. As a precaution, it is recommended to avoid black cohosh in case of pre-existing liver disease, and to stop immediately in case of abdominal pain, dark urine or jaundice.

On this point, the French position is more clear-cut than the pharmacy aisle suggests, and it has to be said. In its opinion of December 14, 2007 on the use in food supplements of plants that have been the subject of pharmacovigilance reports, Afssa (now Anses) examined the European cases of liver injury associated with Cimicifuga racemosa, some of which had required a transplant. Its conclusion: the available scientific evidence leads it to recommend avoiding the consumption of Cimicifuga racemosa as a food supplement, for lack of being able to define safe conditions of use. This opinion has not been replaced by a more permissive text to our knowledge.

The plant also exists in France in the form of a medicine, subject to a marketing authorization. The summary of product characteristics published by ANSM for that product explicitly mentions that cases of liver injury associated with taking black cohosh have been reported, and that treatment must be stopped in case of signs suggesting liver injury. In other words: whether as a supplement or as a medicine, liver vigilance is not a precaution of principle, it is a written instruction.

Evening primrose oil and valerian: thinner evidence

Evening primrose oil is often presented as an essential "feminine" product, but the data on hot flashes are frankly mixed. One trial reported a significant improvement in symptom severity, while another found no difference from placebo on the frequency, duration or severity of hot flashes. A recent synthesis bringing together several randomized trials concludes that any effect is at best limited to courses of less than six months, with no clear benefit beyond⁵.

Valerian, for its part, is studied mainly for sleep rather than for hot flashes as such. A triple-blind controlled trial conducted in postmenopausal women showed a reduction in the severity and frequency of hot flashes after two months of use, compared with placebo⁶. It is an encouraging result, but it rests on a still limited number of trials, which calls for caution before drawing a general conclusion.

What official medicine says

This is where the picture becomes more clear-cut. In 2023, the North American Menopause Society (NAMS), which is authoritative on the subject, published its update of the recommendations on non-hormone treatments for vasomotor symptoms. Its conclusion, without hedging: "supplements and herbal remedies" (including explicitly dietary soy, soy extracts and equol) appear in the list of non-recommended approaches, for lack of evidence judged consistent enough from one trial to another⁷.

This may seem to contradict the meta-analyses cited above, notably on soy. In reality, the two findings coexist: some meta-analyses detect a statistically significant average effect across a large number of combined trials, while a panel of experts, weighing the methodological quality of each study individually, judges that the evidence is not yet solid and reproducible enough to make it an official recommendation. It is an important nuance to know: "an effect measured in a meta-analysis" and "a clinical recommendation" do not answer exactly the same question.

How to choose, if you want to try

None of this means these products should be banned on principle. But a few reflexes limit disappointment and risk:

• Talk to your doctor or pharmacist before starting, especially if you are already on a treatment (antidepressant, anticoagulant, hormone therapy): interactions are poorly documented for many of these plants.
• Prefer a standardized extract, whose label states the amount of the active compound (for example the mg of isoflavones or the isopropanolic extract of black cohosh), rather than a "menopause blend" with no clear dosage.
• Check that you are not in a group set aside by the official opinions. Personal or family history of breast cancer, treated hypothyroidism: isoflavone supplements are not advised or call for medical advice. Known liver disease: black cohosh is to be avoided, and Anses more broadly recommends not consuming it as a food supplement.
• Give yourself a realistic timeframe: effects, when they exist, generally show up after several weeks of continuous use, not after three days.
• Watch your body, particularly with black cohosh: abdominal pain, dark urine, unusual fatigue or jaundice should lead you to stop the product and seek advice.
• Do not expect an effect comparable to hormone therapy. These supplements, at best, ease things: they do not replace medical care if your symptoms are severe.

Fundamentally, the best question to ask is not "does this supplement work?" but "what level of evidence do I have in hand, and is it worth trying for me?". Soy has the best supported file; black cohosh can help some women, with common-sense liver vigilance; evening primrose and valerian remain, for now, more of a bet than a certainty. In every case, discussing it with a health professional remains the best way to weigh your symptoms, your history and what science can really promise.

⚠️ This article is provided for informational and educational purposes only. It does not replace medical advice, diagnosis or treatment. Always consult your doctor or a qualified health professional with any questions about your health.

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