Evidence reviews
Does it actually work?
Each review takes one herb and one condition and goes deep: the trials that tested it, what was taken and for how long, who paid for the research, and who should avoid it.
How to read the ratings
- Good clinical evidence
- Promising clinical evidence
- Early or mixed evidence
- Long traditional use
Ratings apply to that herb for that condition only. The same herb can be well supported for one use and unproven for another. How we rate evidence →
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Withania somnifera
Ashwagandha for Anxiety
Promising clinical evidenceSmall trials of standardized ashwagandha root extracts found lower stress and anxiety scores than placebo over 6 to 12 weeks, mostly in stressed but healthy adults; certainty is low, and rare liver injury and thyroid effects limit who should take it.
7 key studies reviewed
Herbs for Anxiety and Stress → -
Actaea racemosa
Black Cohosh for Hot Flashes
Early or mixed evidenceSome trials of licensed black cohosh extracts report fewer hot flashes, but a Cochrane review and two large year-long trials found no clear benefit over placebo, products vary widely, and rare liver injury has been reported.
7 key studies reviewed
Herbs for Menopause and Hot Flashes → -
Tanacetum parthenium
Feverfew for Migraine
Promising clinical evidenceTaken daily, feverfew may slightly reduce how often migraines happen, by about 0.6 attacks a month more than placebo in its best trial. The evidence is low quality, results are mixed, and it does not treat an attack in progress.
7 key studies reviewed
Herbs for Headaches and Migraine → -
Zingiber officinale
Ginger for Nausea
Good clinical evidenceGinger modestly eases pregnancy nausea in small, low-quality trials and is suggested by ACOG and NICE; results for chemotherapy and postoperative nausea are mixed, and motion sickness evidence is weak.
7 key studies reviewed
Herbs for Nausea → -
Hydrastis canadensis
Goldenseal for UTIs
Long traditional useNo clinical trial has tested goldenseal for urinary tract infections; its berberine acts on E. coli only in the lab, is poorly absorbed, and the herb interacts with common medicines.
7 key studies reviewed
Herbs for Urinary Tract Health → -
Hibiscus sabdariffa
Hibiscus for Blood Pressure
Promising clinical evidenceHibiscus (roselle) tea may modestly lower systolic blood pressure in people with mildly raised readings, but trials are small and short, Cochrane calls the evidence insufficient, and it can interact with medicines.
7 key studies reviewed
Herbs for Heart and Circulation → -
Mentha × piperita
Peppermint for IBS
Good clinical evidenceEnteric-coated peppermint oil capsules eased IBS symptoms and belly pain more than placebo in several meta-analyses and are suggested by guidelines, but the evidence is low quality, recent rigorous trials were mixed, and heartburn is common.
7 key studies reviewed
Herbs for IBS → -
Rhodiola rosea
Rhodiola for Depression
Early or mixed evidenceRhodiola has two small placebo-controlled depression trials with opposite results. A 2022 psychiatry taskforce does not currently recommend it, and case reports describe reactions when it was taken with antidepressants.
6 key studies reviewed
Herbs for Low Mood and Depression → -
Salvia officinalis
Sage for Hot Flashes
Early or mixed evidenceSmall, short trials of sage leaf extracts report fewer or milder menopausal hot flashes, but the products differ, a 2023 meta-analysis was imprecise, and medical treatments work far better.
6 key studies reviewed
Herbs for Menopause and Hot Flashes → -
Valeriana officinalis
Valerian for Sleep
Early or mixed evidenceValerian may help some people feel they sleep a little better after two to four weeks, but objective sleep measures barely change, the most rigorous trials were negative, and US sleep specialists suggest not using it for chronic insomnia.
7 key studies reviewed
Herbs for Sleep →
These pages are educational and are not medical advice. Looking for every herb studied for a concern? Browse the concern guides →