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Small pilot study doesn’t warrant bold claim about fennel for menopause symptoms

Study confirms benefits of fennel in reducing postmenopause symptoms

Our Review Summary

This news release from the North American Menopause Society makes a brief study of fennel in reducing menopause symptoms sound like the final word on the subject — but we’ve seen many other situations where a larger study debunks a short-term small scale study.

The release describes results of a small, 10-week pilot study of 79 Iranian women designed to credibly assess the value of the licorice-like herb in reducing hot flashes, insomnia and other symptoms of menopause.

Although the release includes a cautionary quote at the end calling for further study to support the investigators’ claim of benefit, the headline is far too optimistic for a small pilot study. The release lacks numbers to put the claims in context; cost information and potential harms are also left out.

As a result, it will be tough for the intended audience of journalists, or other readers, to determine whether fennel is a truly effective and safe short- or long-term treatment choice.


Why This Matters

The use of herbal and other non-traditional medicines for treating post-menopausal symptoms has experienced a surge of interest among women whose concerns about hormone therapies are real and understandable. Fennel, a so-called phytoestrogen, has been known anecdotally and in some observational studies to reduce the discomfort of menstrual cramps and has also been taken for menopause symptoms. Thus, news releases and articles about studies that attempt to put some scientific rigor behind alleged benefits will find eager audiences.

Many women suffer from menopause symptoms but avoid taking estrogen supplements because of side effects, cost, or concern about risks. Also, some simply want a little symptom relief from what they regard as a normal aging process. Something as “simple” as a harmless over-the-counter herbal supplement for symptoms seems ideal, doesn’t it?

But because it is difficult for consumers to make an informed choice about safely or effectively taking fennel on the basis of a small pilot study, any news release about it or story derived from it, needs to be approached with caution as well as curiosity.


Does the news release adequately discuss the costs of the intervention?

Not Satisfactory

Fennel supplements are sold in brick and mortar stores and online. Costs are easily established and should have been addressed in the release along with equivalent doses used in the pilot study.

We found 100 mg fennel seed capsules selling on for $9.58 for 100 capsules.

It’s not clear that there is a standard way to assess fennel potency. Is the fennel simply ground up and made into a 100 mg tablet? What should a consumer look for when trying to buy it? The release doesn’t offer any guidance.

Does the news release adequately quantify the benefits of the treatment/test/product/procedure?

Not Satisfactory

We were disappointed to read only very vague terms such as “significant statistical difference” and “improved menopause symptoms” used to describe improvements in hot flashes, sleeplessness, vaginal dryness, and anxiety.

The release could have done better on this score had it told us something about the scales used to measure improvement (What was the minimum and maximum score for hot flashes? The improvement in sleeplessness went from what to what?) and the absolute difference from the beginning of the trial to completion of the trial.

Does the news release adequately explain/quantify the harms of the intervention?

Not Satisfactory

The jury remains out about the potential long-term effects of what some refer to as endocrine disrupters. Readers of this release are told there were no “serious” side effects, but not what the side effects were.

Nor was there any mention of the ongoing scientific debate about the safety of phytoestrogens. Concerns have been raised about tumor promotion in estrogen-sensitive tumors from phytoestrogens (although plant estrogen is actually very weak compared to estrogen used for pharmacologic purposes).

Does the news release seem to grasp the quality of the evidence?

Not Satisfactory

Readers of the release are told the study was “randomized, triple-blind, placebo-controlled,” but the release contains no specific information about how the treatment and placebo groups compared, or the amount and concentration of fennel given in the treatment group.

In addition, a 10-week trial is a very short time-frame for evaluating symptoms which can wax and wane over several years. The release should have acknowledged this.

Does the news release commit disease-mongering?


No mongering of menopause symptoms here. While menopause is a normal phenomenon of aging sometimes symptoms can be severely bothersome.

The release provides some interesting context on the use of alternative and complementary medicine for treating menopause symptoms.

Does the news release identify funding sources & disclose conflicts of interest?

Not Satisfactory

The release doesn’t tell us who funded the study. According to the Iranian Registry of Clinical Trials, the study was funded by Tehran University.

Does the news release compare the new approach with existing alternatives?


The release cites hormone therapy (HT) as the most effective treatment for symptoms, while noting concerns about HT’s potential side effects.

A broader discussion about managing hot flashes (the most bothersome symptom for most women) by avoiding alcohol and spicy foods, wearing layers, and other interventions would have been helpful.

Does the news release establish the availability of the treatment/test/product/procedure?

Not Applicable

We’ll rate this Not Applicable since most readers will likely be aware that fennel can be purchased and that supplements are available. However, as noted above, it’s not clear at all how 100 mg doses are formulated.

Does the news release establish the true novelty of the approach?


The news hook here is that results of this study are billed as “confirmation” of benefits — an overstatement — but also that the study is one of the first undertaken with scientific rigor. It’s hard to say if that is so, but the release makes a reasonable case, albeit based on a very brief trial.

Does the news release include unjustifiable, sensational language, including in the quotes of researchers?


The release doesn’t employ sensational language. However, we do have concerns with the headline, as noted above, since it overstates the findings.

Total Score: 4 of 9 Satisfactory


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