Does Fennel Provide PMS Relief?

by Dr. Daniel J. Heller August 16, 2013

If you follow the news for PMS and PMDD information, you’ll occasionally hear about the latest new supplement or exotic herb being touted as a great breakthrough for women. We covered one of these before when we discussed saffron herb for PMS, which briefly got some attention from the media, and, not surprisingly, from some supplement companies as well.

There’s a new study that joins the ranks of the saffron study for several reasons. It was a small study  comparing the herb fennel to exercise for the treatment of PMS, and of course some media outlets picked up on it. One headline from Europe even trumpeted, “Fennel could help millions of women beat the monthly misery of PMS.” While we like the herb fennel for a variety of reasons, this study doesn’t actually prove very much.

Like the saffron study, this one was done in Iran, where a surprising number of small studies have been done for PMS and herbs. And, kudos to the Iranian researchers who pursue these studies! However, usually these studies on herbs for PMS have similar problems: they’re quite small; they’re not placebo-controlled; and they are poorly designed.

Larger studies are always preferable to smaller studies. In a small study, it is easy to randomly arrive at a conclusion without realizing it is, in fact, random. When studies are done are large groups, it’s less likely that a random result will be confused with something significant.

When a study like the ones on saffron and fennel are not placebo-controlled, we can’t know if the women are helped simply by the belief that they are taking something that may help them. Our post about the powerful effects of placebo helps explain that even difficult conditions like depression can be helped by placebo, and that even supposedly scientific drugs like anti-depressants haven’t been proven superior to placebo. Often, scientific studies from non-westernized countries don’t use a placebo control group, which makes their results much less useful.

The design of a study is crucial to determining whether an herb, drug, technique, or other intervention is in fact useful. In the fennel study, fennel was compared to exercise, and a third group was simply observed (this third group is called “the control” group). Now, as we’ve pointed out before, no one has ever successfully proven that exercise improves PMS symptoms, even though we believe it does. But we know exercise does no harm, and is healthy no matter what. That is different than scientific certainty that it works. So an important flaw in this study is the comparison of one experimental treatment, fennel, with another unproven treatment, exercise, compared to nothing at all (the control group).

Another flaw is the way the researchers gave the fennel extract: three days before and three days after the women, in this case high school girls, got their period. The write up of the study was quite short, so the authors neither explained why they gave a PMS remedy for three days after the period, nor why they gave it for only three days before. Perhaps they didn’t understand PMS very well as we’ve pointed out so many times, many women get their PMS symptoms a week or two or even three weeks before their period. The administration of this potential remedy makes no sense.

Of course, treating only high school girls is a very limited population, so even if they had been successful, it wouldn’t have proven that fennel could work in any other age women. But given the small size of the study, this is only a small objection.

Finally, as is often the case in these studies, the authors conclude that the remedy worked. Given all the flaws in this study, if the herb did appear to work—and the authors concluded it was more effective than the exercise—all that is really reasonable to conclude is that it should be studied again, with an improved design, with proper administration, in a placebo-controlled study.

There are proven natural solutions to PMS and PMDD: Vitex herb, calcium, magnesium, and vitamin B6 all have been shown to be effective in well-designed, placebo-controlled studies. We also have plenty of common-sense suggestions that can help you get a handle on premenstrual suffering.

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The information and contents contained in this Web site has not been evaluated by the FDA. Products are not intended to diagnose, treat, cure, or prevent any disease. If you are pregnant, intend to become pregnant, or nursing, please consult a physician before taking any dietary supplement. If taking prescription drugs, consult your healthcare practitioner prior to use. You must be 18 years or older to purchase products. Individual results do vary.         

About The PMS Comfort Blog

The PMS Comfort Blog is our informal way of keeping you up to date on women’s health issues that we think are important; timely; underappreciated; useful; or just interesting. And, we’ll admit, sometimes we can’t resist poking some good-natured fun at the way the mainstream media portrays health, natural health, and women’s health issues. As always, we’d love to hear from you and are interested in knowing what you think and feel about these or other topics. Leave a comment for us, we’ll always respond. And, if there’s a women’s health topic that’s of interest to you, or that you find confusing, let us know! We want this blog to be helpful to you.


Dr. Daniel Heller is the primary author of this blog, the developer of our PMS Natural Relief Programs, and the founder of He is a holistic naturopathic doctor in Northern California with over 16 years experience helping thousands of women recover from PMS, PMDD, as well as helping women, children, and families find natural answers to all manner of health challenges.


PMS Comfort is here to support you with detailed, practical knowledge presented in a balanced manner you can trust. We are committed to educating, informing, and empowering womenregarding PMS, PMDD, and women’s health, and to providing natural relief for premenstrual symptoms.



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