How effective are natural products at improving muscle strength and function in older adults? (A systematised review of randomized controlled trials)

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Abstract Background and objective: an age-related loss of muscle strength and function is becoming a global concern due to its harmful consequences and limited effective and safe treatments. Several medicinal plants have been indicated to improve muscle strength and vitality traditionally. Therefore, this review aimed to examine the effectiveness of natural products at enhancing muscle strength and function in the elderly. Methods: a systematised review of RCTs of natural products related to muscle strength and functioning in older adults was conducted by searching electronic databases (database inception to March 2020), such as PubMed and in the bibliographies of retrieved trials. The selection, screening, data extraction, and critical evaluation of RCTs were conducted by one author. Main Results: fifteen RCTs were included on ten herbs: Camellia sinesis (green tea), Kaempferia parviflora (KP), Centella asiatica (CA), Viscum album coloratum (Korean mistletoe; KM), Withania somnifera (Ashwagandha), Panax ginseng (PG), Cordyceps sinensis (CS), and Glycyrrhiza glabra (Liqurice flavonoids oil; LFO), Theobroma cacao, and Soy isoflavones. Results revealed green tea exerted synergistic effects to exercise in sarcopenic women. It offered an 11.36% (P=0.010) improved walking ability in the exercise + green tea group compared to the exercise alone group (4.84%, P=0.020). LFO significantly improved the total and trunk muscle mass (P < 0.01) in the elderly with osteoarthritis. It also significantly improved one-leg standing (P= 0.03) in healthy elderly. KP improved the 6-min walk test in healthy elderly significantly (P < 0.05). KM increased knee muscle strength in healthy elderly (P = 0.009 for peak torque and P = 0.033 for total set work). Soy isoflavones improved appendicular free fat mass (P =0.016) and muscle mass index (P=0.037) in sarcopenic-obese postmenopausal women. Cocoa enhanced handgrip strength (P=0.04), the Timed UP and GO test (P=0.03), sit up test (P=0.005), the step test (P=0.02), and the 6-min walk test (P=0.02) in mid-aged and older people. The multi-herbal extract containing PG significantly improved vitality compared to other groups in the healthy elderly (p = 0.028). CS increased the metabolic threshold of healthy elderly when exercising (P=0.006). Ashwagandha improved the anabolic hormones in overweight elderly men, including DHEA-S (P= 0.005) and testosterone (P= 0.010). There was no data documented comparing the benefits of CA to placebo. There were no adverse effects reported related to the natural products that were assessed for their safety. Conclusion: at present, there is low-quality evidence supporting the benefits and safety of green tea for physical ability in sarcopenic women, Liquorice flavonoid oil for muscle mass and body balance in the elderly, and Korean mistletoe for muscle strength in the elderly. There is low-quality evidence for the efficacy but not the safety of Kaempferia parviflora for physical performance and Cocoa for muscle strength and functioning in older adults. Evidence does not currently support the use of for Panax ginseng, Cordyceps sinensis, Withania somnifera, and Centella asiatica for muscle strength and functioning in the elderly. All the medicinal plants reviewed require more rigorous research.