Dietary berberine supplementation improves select physiological and psychological responses during exertional heat stress: A pilot study in young adults

Berberine has been shown to lower core temperature and heart rate during passive heat stress in animal models. This study evaluated the effect of dietary berberine supplementation on physiological and perceptual responses to exercise-heat stress in humans. Eight participants (6 men/2 women; Age: 23 ± 3 years, Stature: 1.75 ± 0.03 m, Mass: 71.8 ± 2.7 kg, VO_2max: 57.5 ± 2.1 mL/kg lbm/min^-1) ingested 1.5 g of Berberine or Placebo for 7d prior to a 1 h treadmill run (60% VO_2max) in hot (35°C), moderately humid (39% RH) conditions. Mean body temperature (T_b), heart rate (HR), expired gasses (VO₂, VCO₂, RER), minute ventilation, respiratory rate (R_R), tidal volume, and perceptual responses (thermal sensation, perceived discomfort, and perceived exertion) were measured throughout exercise. Data are reported as average ± standard deviation over the 60 min exercise trial. T_b was lower (p = 0.030) in Berberine (37.69 ± 0.53°C) than Placebo (37.84 ± 0.38°C). Heart rate was lower (p = 0.025) in Berberine (163 ± 28 bpm) than Placebo (166 ± 30 bpm). R_R was lower (p = 0.045) in Berberine (38.8 ± 11.2 bpm) than Placebo (41.4 ± 10.6 bpm). Thermal sensation was lower (p = 0.002) in Berberine (9.5 ± 4.2) than Placebo (12.3 ± 5.0). Generalized discomfort was lower (p = 0.044) in Berberine (9.3 ± 5.1) than Placebo (12.1 ± 5.6). Perceived exertion was lower (p < 0.001) in Berberine (11.4 ± 3.4) than Placebo (13.1 ± 4.0). Dietary berberine supplementation improved mean body temperature, heart rate, respiratory rate, and perceptual responses during exertional heat stress. Many of these changes were of small magnitude, calling into question the potential utility of dietary berberine supplementation for work or exercise in hot ambient conditions.