Writing in the Journal of Herbal Medicine, a team of Taiwanese researchers shared findings from a recent study investigating the effects of the alpine herb on tolerance to oxygen deprivation as measured by cognitive performance outcomes.
“Hypoxic exposure leads to impaired cognitive function that decreases the performance of pilots in multitasking operations,” they wrote. “Rhodiola crenulata has demonstrated in vitro and in vivo antihypoxic properties. However, its effect on hypoxia-induced cognitive impairment remains unclear.”
The study was supported by grants from the Taiwanese Ministry of Science and Technology and Ministry of National Defense-Medical Affairs Bureau.
Rhodiola for flight safety
Successful flight missions rely on normal cognitive function across mental processes, but oxygen shortages at high altitudes may interfere with optimal attention, memory, speech, problem-solving and judgement despite the pressurized cabin, the researchers noted.
They referenced a 2010 U.S. Army Aeromedical Research Laboratory study showing that even moderate levels of hypoxia significantly degraded the ability of military instructor pilots to perform a precision slow flight task at 18,000 feet.
Previous research has shown that Rhodiola crenulata effectively prevented hypoxia-induced oxidative stress and endothelial damage and increased aerobic exercise performance in hypoxic conditions. Large-scale clinical trials have also demonstrated the potential of the Rhodiola rosea species to enhance cognitive function, memory and attention and decrease fatigue and stress, as well as the formation of hypoxia-induced free radicals.
“We hypothesized that Rhodiola could improve cognitive function under hypoxic conditions by increasing oxygen saturation,” the researchers wrote. “To explore this, we conducted this study, with an aim to improve the overall flight safety of pilots.”
Although much of the existing research has focused on the effects of the Rhodiola rosea species, this study used a Rhodiola crenulata extract manufactured by Sun Ten Laboratories in Taiwan.
Grown primarily in the high-altitude regions of the Tibet, Sichuan and Yunnan provinces in China, Rhodiola crenulata has been used for acute mountain sickness, memory enhancement, work productivity and depression for centuries. Like Rhodiola rosea, it is known for its potent adaptogenic properties but has been found to have a higher phytochemical content and antioxidant activity since it grows under harsher conditions at higher altitudes.
The repeated-measures study recruited 39 healthy adults (25 men and 14 women) and administered either two capsules (1,254 mg total) of Rhodiola crenulata extract (RCE) or a placebo 48 hours before performing a battery of cognitive tasks under normal oxygen concentration (normoxic) and low oxygen conditions (hypoxic) at atmospheric pressure.
Participants completed four sessions (normoxia, RCE, hypoxia, and hypoxia + RCE) in a randomized order and switched groups after a two-week washout period.
In each trial, subjects wore a medical-grade PVC oxygen breathing mask supplied with 7% oxygen for 30 minutes at an ambient pressure of 760 mmHg to induce normobaric hypoxia. A fraction of inspired oxygen (FiO2)—the concentration of oxygen in the gas mixture—was calculated as 49.91 mmHg, which is equivalent to breathing air at an altitude of 25,000 feet. Blood oxygen saturation level (SpO2), symptoms by questionnaire and stress saliva were also used to evaluate outcomes.
“We found that pretreatment with RCE effectively prevented oxygen saturation and hypoxia-impaired cognitive function,” the researchers concluded. “Moreover, we found that pretreatment with RCE significantly attenuated the severity of hypoxia-induced acute mountain sickness.”
For future study, they suggested comparing the effects of Rhodiola crenulata to acetazolamide, the only drug approved by the U.S. Food and Drug Administration for acute mountain sickness (AMS) but shown to impair neuropsychological function during high-altitude exposures.
Source: Journal of Herbal Medicine
“Rhodiola crenulata extract supplement significantly attenuates hypoxia-reduced oxygen saturation and cognitive function”
Authors: Shih-Yu Lee et al.