Benefits
Bowel symptom scores with a wormwood-containing blend
In a 10-week double-blind trial of 40 adults with Crohn's disease on steroids, a herbal blend containing wormwood (500 mg three times daily) was added while steroids were tapered off. At week 8, 13 of 20 on the blend had almost complete symptom remission vs none on placebo, and steroids were restarted in 2 of 20 vs 16 of 20. The blend's other herbs are not named.
Blood TNF-alpha, a marker of inflammation
In a 6-week controlled trial of 20 adults with Crohn's disease, 750 mg of dried powdered wormwood three times daily added to usual treatment lowered average serum TNF-alpha from 24.5 to 8.0 pg/ml, vs 25.7 to 21.1 in controls. Symptom remission occurred in 8 of 10 vs 2 of 10. The abstract does not describe blinding.
Mood scores tracked alongside bowel symptoms
Both trials also used the Hamilton Depression Scale, and mood scores improved with wormwood as bowel symptoms improved. Mood was a secondary measure in people with Crohn's disease; no trial has tested wormwood for mood on its own.
Appetite and digestion as a bitter herb
The EU recognizes wormwood as a traditional remedy for temporary loss of appetite (taken 30 minutes before meals) and mild digestive complaints (taken after meals), based on long-standing use. In 12 volunteers, water flavored with 1500 mg of wormwood changed blood flow responses early in digestion, but no trial has measured appetite or digestive comfort.
Traditional use against worms: lab and livestock research
The common name reflects old use against intestinal worms. Wormwood extracts killed or paralyzed several worm species in lab tests and in rats, and cut worm egg counts in sheep, but there are no human trials, so it is not a substitute for medical treatment of a confirmed infection.
Mechanism of action
Lower blood TNF-alpha in one trial
In the 6-week trial in Crohn's disease, serum TNF-alpha, a signaling protein that drives inflammation, fell by about two thirds with wormwood and changed little in controls. The authors cited earlier lab studies in which wormwood extracts suppressed TNF-alpha and other interleukins; the compounds responsible were not identified.
Thujone blocks the GABA-A receptor
In mouse, fly and rat nerve cell studies, alpha-thujone blocked the GABA-gated chloride channel, the brain's main calming receptor; poisoning signs in mice resembled those of the convulsant picrotoxinin and were eased by diazepam or phenobarbital. Mouse liver enzymes quickly converted thujone to less toxic metabolites. Thujone levels in historic absinthe were below seizure thresholds.
Bitter taste and the early phase of digestion
Bitter compounds are thought to trigger reflex release of gastric juice, bile and pancreatic juice, with effects mainly in people with low digestive secretions. In volunteers, wormwood-flavored water raised peripheral vascular resistance and lowered cardiac output after drinking, while bitter capsules that bypass taste did not change these responses.
Activity against worms in lab and animal studies
Wormwood extracts were active against Trichinella spiralis, Ascaris suum and Haemonchus contortus in lab and animal studies; in sheep, an ethanol extract at 2 g/kg body weight cut fecal worm eggs by about 90%. How it works is not established, and it has not been tested in people.
Liver protection in rats
In rats, a wormwood extract (500 mg/kg) given before acetaminophen lowered liver enzyme levels and deaths, but it did not protect against carbon tetrachloride damage. This has not been tested in people, and the EU monograph advises against wormwood in liver disease.
Clinical trials
Controlled trial in which 10 randomly selected patients took 750 mg of dried powdered wormwood three times daily for 6 weeks on top of their usual therapy and 10 randomly selected patients served as controls; the abstract calls the control group placebo but does not describe blinding. Patients on infliximab or similar drugs were excluded, and other medicines were kept at baseline doses. (Krebs et al. 2010, Phytomedicine)
20 adults with Crohn's disease and a Crohn's Disease Activity Index (CDAI) of at least 200.
Serum TNF-alpha fell from 24.5 to 8.0 pg/ml with wormwood vs 25.7 to 21.1 in controls. CDAI fell from 275 to below 175 with wormwood vs 282 to 230 in controls, with symptom remission in 8 vs 2 patients. Quality of life (IBDQ) and Hamilton Depression Scale scores also improved with wormwood. Small trial from one research group.
Double-blind, placebo-controlled trial at five sites in Germany: a herbal blend containing wormwood herb, 500 mg three times daily, or placebo for 10 weeks, with steroids tapered to zero by week 10 and follow-up to week 20 without trial medication. Outcomes: CDAI, Inflammatory Bowel Disease Questionnaire, Hamilton Depression Scale and a visual analogue scale. (Omer et al. 2007, Phytomedicine)
40 adults with Crohn's disease on a stable steroid dose (40 mg prednisone equivalent or less), 20 per group.
Symptoms improved steadily in 18 of 20 on the blend despite steroid tapering. At week 8, 13 of 20 (65%) on the blend had almost complete remission vs none on placebo, lasting to week 20. Steroids were restarted in 2 of 20 on the blend vs 16 of 20 on placebo. The abstract does not name the blend's other ingredients.
Open, uncontrolled pilot trial: 1.8 g/day of a thujone-free wormwood preparation for 6 months added to ongoing dual renin-angiotensin system blockade, then 6 months of follow-up without wormwood. (Krebs et al. 2010, Am J Kidney Dis)
10 adults with biopsy-proven IgA nephropathy, normal kidney function and urine protein of 500 to 3,500 mg/day for at least 3 months.
Urine protein-to-creatinine ratio fell from 2,340 to 315 mg/g (p<0.001) and stayed stable during follow-up; estimated filtration rate was unchanged and mean arterial blood pressure fell moderately (p<0.002). With no control group and 10 patients, the change cannot be firmly attributed to wormwood.