What Is Feverfew and Why Is There Concern?
Feverfew, scientifically known as Tanacetum parthenium, is a plant with a long history of use in traditional and folk medicine, primarily for treating fevers and migraines. In recent decades, it has gained popularity as a natural alternative for migraine prevention, with its active compounds, particularly parthenolide, believed to possess anti-inflammatory properties. The concern about weight gain stems from the general list of potential side effects often associated with the herb, based largely on anecdotal reports rather than robust clinical data. This has left many users confused about whether they should be worried about changes in their weight.
The Evidence for Weight Gain: Anecdotal vs. Clinical Reporting
Many reputable medical websites, such as Drugs.com, WebMD, and RxList, include weight gain in their lists of possible feverfew side effects. This information is typically gathered from a collection of user-reported adverse events. While valuable, this type of anecdotal data can be less reliable than controlled clinical studies for establishing a direct causal link. User-reported weight changes could be influenced by a wide variety of factors, including other medications, dietary habits, or unrelated health conditions. The possibility of weight gain is acknowledged, but its frequency and whether it's directly caused by feverfew is unclear based on these reports alone.
The Evidence Against Weight Gain: A Review of Clinical Trials
A systematic review published in 2025, which provided an update on the efficacy and safety of feverfew for migraine prevention, offers a contrasting view. The review explicitly stated that feverfew did not appear to affect body weight in the clinical trials included in the analysis. This finding from controlled studies suggests that, at least within the parameters of these trials, there was no statistically significant evidence of a weight-altering effect. This does not mean that weight gain is impossible for every individual, but it does question its status as a common or direct side effect. It highlights the difference between statistically significant clinical findings and potentially coincidental or anecdotal reports.
The Parthenolide Paradox: An Anti-Obesity Possibility?
Adding another layer of complexity to the issue is the research on parthenolide, one of feverfew's primary active compounds. A study published in Pharmacological Research in 2019 investigated the effects of parthenolide on obesity in high-fat diet-fed mice. The results were surprising: the mice administered parthenolide showed a significant reduction in body weight and adipose tissue. This anti-obese effect was linked to anti-inflammatory and antioxidant responses mediated by the Nrf2/Keap1 signaling pathway. This finding creates a fascinating paradox. While some human reports link the whole herb to weight gain, a key component shows a potential anti-obesity effect in animal models. It is crucial to remember that animal study results do not always translate directly to humans, and the complex interaction of all compounds in the feverfew plant is different from studying an isolated chemical.
Potential Causes of Weight Fluctuation While Taking Feverfew
If feverfew isn't directly causing weight gain, what could be the contributing factors for those who report it? Several other side effects of feverfew could indirectly influence body weight:
- Gastrointestinal Issues: Feverfew is known to cause stomach upset, nausea, bloating, and other digestive problems. Bloating can lead to temporary weight fluctuations, and chronic digestive discomfort could impact eating habits.
- Fatigue: Some users report fatigue as a side effect. Reduced energy levels could lead to decreased physical activity, which over time could contribute to weight gain.
- Changes in Appetite: Any alteration in digestive comfort can affect appetite. Nausea might decrease it, but for others, different symptoms could lead to a change in caloric intake.
- Other Medications: Many individuals taking feverfew for migraines may also be on other medications that could be a true source of weight gain, making it difficult to pinpoint the cause.
Feverfew Weight Effects: Anecdotal Reports vs. Clinical Studies
| Aspect | Anecdotal Reports (User-Reported) | Clinical Studies (Systematic Review) |
|---|---|---|
| Effect on Weight | Some users report weight gain, listed as a side effect on health websites. | Found no statistically significant effect on body weight in reviewed trials. |
| Evidence Strength | Lower; based on self-reported experiences and association. | Higher; based on controlled, systematic investigation of trial data. |
| Prevalence | Unclear; likely affects a subset of users, though not specified. | Low to none; effect not observed in trial participants on average. |
A Note on Long-Term Use and Safety
Most studies on feverfew have focused on short-term use, typically up to four months. The safety of long-term use beyond this period is not well-established. Furthermore, some individuals have reported a "post-feverfew syndrome" upon stopping the herb, characterized by muscle stiffness, anxiety, and a rebound of migraine symptoms.
Other Common Side Effects of Feverfew
For those considering feverfew, it's helpful to be aware of other more consistently reported side effects:
- Digestive issues: Upset stomach, heartburn, nausea, bloating, gas, diarrhea, or constipation.
- Mouth and Skin: Mouth ulcers, swelling of the mouth, or skin rashes, especially if chewing fresh leaves.
- Allergic Reactions: Particularly for those sensitive to plants in the daisy family (e.g., ragweed, chrysanthemums).
- Neurological: Headaches, dizziness, nervousness, or trouble sleeping.
Conclusion: Does Feverfew Cause Weight Gain?
Based on the available evidence, the link between feverfew and weight gain is inconclusive. While some authoritative health websites list weight gain as a potential side effect based on user reports, more controlled clinical trial data has not established a definitive causal link. For most individuals, weight gain is likely not a direct result of taking feverfew, but could be a secondary effect of other symptoms like fatigue or gastrointestinal issues. Those with concerns should consult a healthcare provider before starting or stopping any supplement. As with any herbal remedy, individual responses can vary significantly. For more information, you can visit the National Center for Complementary and Integrative Health.
