In a 110-person randomized controlled trial, Quercetin supplementation (500 mg daily) reduced acute mountain sickness incidence from 25% to 2% when ascending to high altitude. The findings are encouraging but come with caveats: the study was small, enrolled only young men, and used a proprietary food bar formulation.
Acute mountain sickness (AMS) affects roughly half of lowlanders who ascend rapidly above 2,500 meters. The condition arises when the body struggles to adapt to lower oxygen availability, producing symptoms like headache, nausea, and fatigue. Proper acclimatization helps, but some people develop AMS despite gradual ascent. This double-blind, placebo-controlled trial tested whether Quercetin, a plant flavonoid with antioxidant properties, could reduce both the occurrence and severity of AMS during a controlled high-altitude exposure.
The study enrolled 110 healthy men (average age 27) who ascended from near sea level (440 m) to 3,048 meters over the first week, then to 3,750 meters by day 15. Half received a food bar containing 500 mg Quercetin daily for 15 days (starting two days before ascent); half received an identical-tasting placebo bar. The quercetin group showed a striking difference: only 2% developed AMS by the end, compared to 25% in the placebo group. The severity of AMS symptoms (measured by Lake Louise Scoring) was also significantly lower in the supplemented group.
Beyond AMS incidence, the quercetin group demonstrated several physiological advantages. Arterial oxygen saturation was notably higher (94.0% versus 90.02%, p < 0.001), suggesting better oxygen delivery to tissues at altitude. Both systolic and diastolic blood pressure were lower in the quercetin group (8 mm Hg and 4 mm Hg reductions, respectively, p < 0.001). Blood markers of oxidative stress improved as well: the quercetin group showed reduced malondialdehyde (an oxidative stress marker) and maintained glutathione levels, indicating less free radical damage. Plasma endothelin-1, a hormone involved in blood vessel constriction, was significantly lower in the supplemented group (p < 0.001), which may explain improved oxygen delivery.
Hemoglobin and hematocrit levels improved slightly in the quercetin group, supporting better oxygen-carrying capacity. Body composition, heart rate at rest, and physical performance on a six-minute walk test showed no significant differences between groups, suggesting the effects were specific to altitude adaptation rather than broad changes in fitness or metabolism.
The results are genuinely promising for anyone planning rapid high-altitude travel, particularly mountaineers or trekkers with limited acclimatization time. The effect size is large: going from 25% AMS incidence to 2% is clinically meaningful. However, several limitations warrant caution before supplementing.
First, this trial enrolled only young, healthy men aged 20-40. Whether Quercetin works similarly in women, older adults, or people with underlying health conditions remains unknown. Second, the study used a specific food bar formulation (500 mg quercetin), not standard capsules or powders. It is unclear whether other formulations or dosing schedules would produce the same benefit. Third, the sample size is modest (55 per group), so the true effect could be somewhat smaller in a larger population.
If you are planning a rapid ascent above 3,000 meters and want to explore Quercetin prophylaxis, discuss timing and dosing with your doctor. This study used 500 mg daily starting two days before ascent and continuing for at least 15 days. Standard acclimatization practices—gradual ascent, adequate hydration, rest days, and avoiding alcohol—remain the foundation. Quercetin may be a useful adjunct, not a replacement.
The mechanistic findings (reduced oxidative stress, lower endothelin-1, improved oxygen saturation) align with how Quercetin is thought to work: as an antioxidant and mild vasodilator. This strengthens confidence in the main finding, though ultimately only larger, more diverse trials can confirm generalizability.
| Characteristic | Details |
|---|---|
| Design | Double-blind, randomized, placebo-controlled trial |
| Sample size | 110 participants (55 per group) |
| Population | Healthy lowland men, age 20-40 (mean 26.9 years) |
| Intervention | 500 mg quercetin food bar daily for 15 days (starting 2 days pre-ascent) |
| Control | Identical placebo food bar |
| Altitude profile | Baseline: 440 m; Day 7: 3,048 m; Day 15: 3,750 m |
| Primary outcome | AMS incidence and severity (Lake Louise Scoring) |
| Key secondary outcomes | SpO2, blood pressure, hematological markers, oxidative stress markers |
| Journal | European Journal of Nutrition |
| PubMed ID | 42435069 |
Study: "Quercetin prophylaxis in prevention of acute mountain sickness (AMS): a randomized, double blind, placebo controlled phase-II clinical trials." European Journal of Nutrition. PubMed: 42435069
ProtocolEngine provides general health information based on published research. This is not medical advice. Consult a healthcare professional before starting any supplement or health protocol.