New research reveals how everyday supplements like protein, creatine, and vitamin D may help keep muscles strong, but scientists say the supplements are not quick fixes.
Study: Can Dietary Supplements Support Muscle Function and Physical Activity? A Narrative Review. Image credit: Inside Creative House/Shutterstock.com
A review article published in the journal Nutrients provides in-depth information on the usefulness of dietary supplements in maintaining muscle health among non-athletic adults.
Muscle health matters
Physical activity is a vital lifestyle factor that helps maintain muscle function, control body weight, reduce stress, improve sleep quality, enhance cognitive and physical performance, and lower the risk of various chronic diseases.
Diet is another vital lifestyle factor that helps keep a person physically active by improving muscle mass and activity. Athletes commonly rely on dietary supplements to increase muscle mass, enhance performance, and improve recovery. Good muscular activity is also essential for non-athletes to perform daily life activities, improve the quality of life, and maintain positive aging.
The current review aims to explore the potential benefits and limitations of dietary supplements, as well as the potential harms of some commonly proposed dietary supplements in non-athlete adults.
Muscle homeostasis
Maintenance of muscle mass requires a balance between protein synthesis and breakdown. The rate of muscle mass synthesis is primarily driven by dietary protein intake and physical activity. Muscle protein breakdown, on the other hand, is triggered mainly by inflammation, physical inactivity, and illness.
Inflammation is a key factor in maintaining muscle balance. In older adults, persistent low-grade inflammation is common, and age-related rises in pro-inflammatory molecules can suppress muscle protein synthesis while increasing protein breakdown. Collectively, these changes increase the risk of a range of age-related disorders, including sarcopenia (a condition characterized by the progressive loss of muscle mass, strength, and function with age).
Gut microbiota dysbiosis, characterized by a reduced abundance of beneficial anti-inflammatory microbes and an increased abundance of pro-inflammatory microbes in the gut, significantly contributes to systemic inflammation, impaired nutrient absorption, and altered muscle metabolism.
The composition and diversity of gut microbiota, as well as the levels of microbiota-derived metabolites, can potentially affect skeletal muscle function by modulating inflammation. Conversely, pathophysiological changes in skeletal muscle can affect the diversity of gut microbiota. The term gut-muscle axis is used to describe this bidirectional association between gut microbiota and skeletal muscle.
Association of physical activity with dietary habits and supplements
A synergistic interplay between diet, physical activity, and dietary supplementation is crucial for maintaining body composition, supporting muscle function, and improving overall health. Supplements, such as calcium, vitamin D, omega-3 fatty acids, and whey protein, when combined with regular physical activity, have been shown to significantly enhance muscle mass and bone density, and reduce the risk of age-related muscle degeneration in middle-aged and older women.
Dietary supplements are widely used in nutritional strategies to improve muscle function, strength, performance, and muscle recovery in sports and exercise. However, evidence for their effectiveness in non-athletes remains limited and variable, and the physiological requirement and dosage of supplements may vary according to the level of physical activity, age, nutritional deficit, and presence of comorbidities.
Protein is one of the most popular dietary supplements primarily used for promoting muscle growth and repair after exertion. Besides professional or recreational athletes, sedentary older people require protein supplements to compensate for age-related muscle mass loss and bone mineral loss, and reduce the risk of fracture and other complications such as sarcopenia. Menopausal women with hormone–loss–related sarcopenia also require protein supplements for muscle growth and maintenance.
Amino acid derivatives, such as creatine and leucine, are widely used supplements in sports and exercise. Creatine supplements, when combined with resistance training, have been shown to increase muscle mass and strength, as well as improve daily life activities. Supplementation alone is usually less effective than when combined with regular exercise. Creatine supplements have also been found to benefit post-menopausal women who experience lower levels of estrogen and resultant loss of muscle mass and bone strength.
Several studies have linked leucine supplements with positive sarcopenia outcomes. Leucine, in combination with resistance training, has been found to improve muscle function and reduce muscle loss in elderly patients with sarcopenia. Due to age-related anabolic resistance, older people require approximately twice as much dietary leucine as young adults to achieve similar increases in muscle protein synthesis.
β-hydroxy-β-methylbutyrate is a leucine metabolite that the International Society of Sports Medicine has endorsed as a safe dietary supplement across various populations, including athletes, non-exercising and sedentary individuals, and patients with sarcopenia. Recent evidence supports its effectiveness in enhancing muscle protein synthesis, reducing protein breakdown, and improving muscle strength and function. Real-world benefits still require confirmation through larger, long-term studies.
L-Carnitine is another amino acid derivative that has been found to prevent muscle damage and facilitate muscle recovery through its antioxidant properties. It has also been found to improve physical performance by reducing lactate production and increasing plasma glucose. There are potential safety concerns with excessive intake, including elevated levels of trimethylamine-N-oxide (TMAO), which have been linked to cardiovascular risk.
Magnesium supplements in healthy elderly women have been found to improve physical performance and conserve skeletal muscle mass and strength. Similarly, potassium supplements have been shown to have potentially beneficial effects on bone and muscle health in patients with sarcopenia. In older women, potassium supplements have been found to optimize muscle contraction, reduce fatigue, and improve adaptation to hormone replacement therapy; however, the evidence remains mixed, and effects may differ between men and women.
Associations between dietary supplements and gut microbiota
The gut microbiota is bidirectionally associated with micronutrients, including vitamins and minerals. The rate of intestinal absorption and bioavailability of micronutrients is regulated by gut microbiota. Micronutrients can alter the composition and function of microbiota when consumed as dietary supplements.
Existing evidence indicates that magnesium supplements can significantly increase the abundance of beneficial bacteria in the gut. Similarly, vitamin D has been found to increase gut microbiota diversity and improve gut health. Supplements like β-hydroxy-β-methylbutyrate and curcumin have been found to increase the abundance of beneficial bacteria, reduce the growth of harmful bacteria, and enhance the production of beneficial metabolites by gut bacteria, including short-chain fatty acids.
There is emerging evidence for the use of probiotic and prebiotic combinations (“synbiotics”) that may indirectly improve muscle function by supporting gut health, although clinical data remain preliminary.
Safety profile of dietary supplements
The duration of supplementation is a crucial determinant of nutrient efficacy. Long-term protein supplementation has been shown to have a negative impact on the gut microbiota. However, there is a lack of evidence regarding possible associations between dietary supplements, gut microbiota composition, and clinical parameters of physical function.
Dietary supplements are not considered medicines and can therefore be introduced to the market without undergoing clinical trials. Although not medicines, some of these supplements can have mild side effects, including gastrointestinal disturbances, nausea, vomiting, and headache. However, high-dose or long-term dietary supplementation can have serious consequences, including liver damage, kidney disease, and birth defects.
Therefore, when considering dietary supplements, it is essential to adhere to the recommended dosage, recognize that product quality and regulatory oversight can vary, seek medical advice regarding potential side effects or drug interactions, and obtain supplies from reliable sources. Some multi-ingredient formulations may have synergistic effects, but require more rigorous testing to confirm their safety and efficacy.
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