Dietary Berberine Supplementation Reduces Body Temperature, Heart Rate, And Perceived Exertion During Exercise-Heat Stress

PURPOSE: Berberine is a plant compound that has multiple pharmacological benefits and has been used in traditional Chinese medicine for centuries. Recent research has shown body temperature improvements and other physiological benefits in mice that were subjected to passive heat stress, but whether these benefits might be extended to humans during exercise-heat stress is currently unknown. METHODS: Five men and two women (mean ± SD: Age 22.7 ± 3.4 years, height 173.3 ± 2 cm, mass 71.6 ± 3.1 kg, VO2max 51.4 ± 2.8 ml·kg-1·min-1, body composition 12.2 ± 2.3% body fat) ingested 1.5 g of Berberine or Placebo for 7 d prior to a 1 hr treadmill run (60% VO2max) in hot ambient conditions (35 °C & 35% RH). Blood samples were collected before (Pre), immediately following (Post), 1 hr (1-Post), and 3 hr after (3-Post) exercise. Core, shell, and mean body temperatures, heart rate, expired gasses, and ratings of perceived exertion, thermal sensation, and perceived discomfort were measured throughout exercise. RESULTS: Berberine supplementation reduced mean skin temperature (p = 0.03) from 50-60 minutes of exercise (Berberine: 34.81 ± 1.22 °C; Placebo: 35.12 ± 0.71 °C). Mean body temperature also trended lower (p = 0.08) following Berberine supplementation (Berberine: 37.60 ± 0.50 °C; Placebo: 37.74 ± 0.27 °C). Heart rate was reduced (p < 0.01) following Berberine supplementation (Berberine: 158 ± 22 bpm; Placebo: 161 ± 23 bpm). VE/VO2 trended lower (p = 0.14) following Berberine supplementation (Berberine: 26.0 ± 1.1 L/min; Placebo: 27.5 ± 3.0 L/min). Ratings of perceived exertion were lower (p < 0.01) from 25 through 60 min of exercise in Berberine (13.2 ± 2.6) as compared to Placebo (15.8 ± 2.6). Thermal sensation was also lower (p = 0.03) from 25 through 60 min of exercise in Berberine (12.0 ± 3.2) as compared to Placebo (15.4 ± 3.3). Perceived discomfort also trended lower (p = 0.07) in Berberine (10.7 ± 4.6) as compared to Placebo (13.9 ± 4.6). CONCLUSION: Collectively, our data suggest that 7 d berberine supplementation improves heart rate, body temperatures, generalized and thermal discomfort during exertional heat stress. It may also improve ventilatory efficiency and perceived discomfort. These changes may enhance an individual's ability to maintain prolonged aerobic exercise under hot, dry ambient conditions.