Benefits
Post-Surgical Pain and Swelling
Four meta-analyses of small trials after wisdom tooth surgery all found less pain with bromelain at some point after surgery, though at different time points, and they split evenly on whether swelling improved. Small placebo-controlled trials after nose and eyelid surgery found less bruising or less swelling. Germany licenses a low-dose bromelain tablet as an add-on for swelling after operations and injuries.
Sinus comfort as an add-on to standard care
A review of herbal medicines for sinusitis found three decades-old randomized trials in which bromelain added to standard care improved some symptoms of acute sinusitis. The reviewers called this encouraging but found limited evidence for herbal medicines in sinusitis overall. A later 12-person study in chronic sinusitis had no control group.
Joint Comfort (Not Supported for Bromelain Alone)
The one placebo-controlled trial of bromelain alone in knee osteoarthritis, 800 mg a day for 12 weeks, found no benefit over placebo on its main score. A trial of bromelain after exercise-induced muscle soreness found no effect on pain, range of motion or strength, and a large ankle sprain trial found a bromelain, trypsin and rutoside blend no better than placebo.
Protein Digestion
Bromelain digests protein and appears in many digestive enzyme blends. In an early crossover study in 12 adults with pancreatic insufficiency, a pancreatic enzyme product with a bromelain shell improved fat absorption more than a standard product and gave an earlier, higher peak in a marker of protein digestion, though the total effect was similar; the authors credited the added bromelain.
Mechanism of action
Protein-Cutting Enzymes
Bromelain is a mixture of cysteine proteases, enzymes that cut proteins. It is reported to inhibit platelet aggregation and to have anti-inflammatory effects in laboratory work; how much of this happens in people at supplement doses is unknown.
Limited Absorption
In 19 healthy men taking 3 g a day, intact and partly active bromelain was detected in plasma at up to about 5 ng/mL, bound to the blood's own protease inhibitors. Doses in most supplements are far lower than 3 g.
Effects on Clotting and Drug Metabolism
A small 1999 study found that oral bromelain lengthened one clotting test (aPTT) from 38 to 46 seconds in healthy donors, and bromelain strongly inhibited CYP2C9, the liver enzyme that clears warfarin, in a laboratory study. These findings are the basis for caution with blood thinners.
Clinical trials
Systematic review and meta-analysis of six randomized placebo-controlled trials of oral bromelain after lower third molar surgery (Liu et al. 2019, J Oral Maxillofac Surg).
Patients having impacted lower wisdom teeth removed; six RCTs.
Bromelain reduced facial swelling early and late after surgery and reduced pain at day 7, but not in the first 2 to 3 days, and had no effect on mouth opening. Three other meta-analyses published in 2019 agreed on some pain benefit but disagreed on its timing and on swelling.
Randomized, double-blind, placebo-controlled pilot trial of bromelain 800 mg a day for 12 weeks (Brien et al. 2006, QJM).
47 adults with moderate to severe knee osteoarthritis; 31 completed.
No significant difference from placebo on the total WOMAC score, its subscales, or quality of life. Both groups improved on the disability subscale. The authors concluded that bromelain was not efficacious as an add-on treatment for moderate to severe knee osteoarthritis.
Systematic review of randomized trials of herbal medicines for rhinosinusitis, including three trials of bromelain (Guo et al. 2006, Otolaryngol Head Neck Surg).
Three decades-old randomized trials of bromelain in acute or mixed sinusitis.
All three bromelain trials reported some positive findings, and pooling the two in acute sinusitis suggested that bromelain added to standard care improved some symptoms. The reviewers called the evidence encouraging for bromelain as an add-on in acute sinusitis, while judging the evidence for herbal medicines in sinusitis limited overall; the median quality score across all the herbal trials reviewed was 3 out of 5.
Double-blind, randomized, placebo-controlled factorial trial of a bromelain, trypsin and rutoside combination against double combinations, single ingredients including bromelain alone, and placebo (Kerkhoffs et al. 2004, Br J Sports Med).
721 patients with acute lateral ankle sprain.
The combination was not superior to placebo, the double combinations or the single ingredients. At day 7, pain fell by a median 60.3% with the combination and 73.3% with placebo, and range of motion improved most with placebo. Only a small subgroup who did not wear a brace did better on the combination.