Commonly known as elephant grass or napiergrass, Pennisetum purpureum Schumach is widely grown in Taiwan, where it is primarily used as livestock feed.
However, in recent years, the plant has been used as an ingredient in health beverages for its antioxidative benefits.
The study, published in the International Journal of Medical Sciences (IJMS), would be the first to evaluate the plant’s efficacy in managing sarcopenia or related muscle decline. The study was conducted by researchers from Taipei Medical University, Tungnan University and Japan’s Hosei University.
A total of 35 participants were randomized to take a capsule containing 300mg of Pennisetum purpureum Schumach or a placebo three times daily for 12 weeks.
The Pennisetum purpureum Schumach extract used in this study was sourced locally from Hualien County and was produced by Natural Keeper Enterprise Co., Ltd.
To measure the effects of the plant extract, researchers took anthropometric measurements, body composition analysis, blood pressure monitoring, hormone profiling, liver and renal function tests, conducted physical performance evaluations, and collected a three-day dietary record of the participants at weeks eight and 12 of the study.
Hand grip strength improvement
Findings showed a significant increase in grip strength in the intervention group after weeks eight and 12 of supplementation as compared to baseline.
Specifically, hand grip strength in the intervention group increased from the baseline of 18.74 ± 5.61kg to 22.48 ± 5.61 at week eight and further went up to 23.51 ± 6.38 at week 12.
No significant changes were seen in hand grip strength in the placebo group throughout the 12-week study.
Despite the significant improvements in hand grip strength, the supplementation of Pennisetum purpureum Schumach extract did not lead to a significant improvement in the other aspect of physical function - the 10-m walk test in this case.
“These results indicate that continuous supplementation of Pennisetum purpureum Schumach at a daily dose of three times 300 mg for 12 weeks has a positive effect on grip strength but does not improve performance in the 10-meter walk test," the researchers wrote.
As to the potential reasons for the improvement in grip strength, the researchers wrote that this could be due to the plant’s antioxidant properties.
According to the researchers, oxidative stress is known to impair skeletal muscle performance by disrupting mitochondrial function, accelerating protein degradation, and suppressing anabolic signaling.
“Bioactive compounds in Pennisetum purpureum Schumach, including polyphenols and anthocyanins, may counteract oxidative stress by scavenging free radicals and improving redox homeostasis, potentially helping to preserve testosterone levels, as oxidative stress can impair Leydig cell steroidogenesis,“ they wrote. ”This sequential pathway, from antioxidant defense to hormonal modulation and subsequently enhanced neuromuscular performance, provides a plausible explanation for the observed findings.”
However, they also cautioned that this proposed mechanism of the plant extract remains speculative and warrants further investigation, as the study did not directly measure oxidative stress biomarkers, mitochondrial function, or neuromuscular activation.
No significant changes in anthropometric measurements
At the same time, Pennisetum purpureum Schumach supplementation also did not lead to significant improvements in anthropometric measurements, including upper arm circumference.
On the other hand, while body mass index and thigh circumference did increase, these were observed in both the intervention and placebo groups, which meant that these improvements were not due to the supplementation of Pennisetum purpureum Schumach.
Upward trend in testosterone levels
Taking the plant extract was found to be associated with a slight upward trend in testosterone levels among male participants with low muscle mass.
However, overall, no significant changes in hormonal levels - including that of testosterone - were seen in both the intervention and placebo groups.
The use of the plant extract also did not cause significant changes in liver function and kidney function, which the researchers said suggested that it may serve as a safe, plant-derived option for enhancing muscle strength in individuals with early signs of muscle decline.
They suggested that future study could investigate the supplement’s synergistic effects when combined with resistance training and explore its efficacy in larger and more diverse populations, including older adults and individuals with chronic conditions.
Source: International Journal of Medical Sciences, 23(3), 963-971. doi: 10.7150/ijms.124224. "Pennisetum purpureum Schumach Supplementation Enhances Grip Strength in Adults with Low Muscle Mass: A Randomized Controlled." Authors: Huang, S.W. et al.
