Effects of protein supplementation
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Protein Supplementation and Muscle Mass Gains
Protein supplementation is widely recognized for its role in supporting muscle mass, especially when combined with resistance training. In healthy adults, protein supplements significantly enhance gains in muscle mass and strength during prolonged resistance exercise training, with the most notable effects seen in resistance-trained individuals and diminishing returns at protein intakes above approximately 1.6 grams per kilogram of body weight per day . For untrained individuals, protein supplementation alone has little impact during the initial weeks of training, but as training becomes more frequent and intense, protein can promote muscle hypertrophy and strength gains . In older adults, protein supplementation can improve muscle mass, particularly in community-dwelling populations, though the specific dose, frequency, or timing of supplementation does not significantly alter this effect . However, in nonfrail older adults with already sufficient protein intake, supplementation does not lead to significant improvements in muscle mass or strength .
Protein Supplementation and Muscle Strength
Protein supplementation, especially when paired with resistance training, leads to significant improvements in muscle strength in both young and older adults 2410. The benefits are more pronounced in those who are already resistance-trained and decrease with age . In older adults, the combination of protein supplementation and heavy resistance training is most effective for increasing muscle size and strength, while protein supplementation alone does not yield significant benefits . The type of protein, such as whey or milk protein, may also influence outcomes, with whey protein showing the best results when combined with resistance training, though findings are inconsistent 710.
Protein Supplementation and Physical Performance
The impact of protein supplementation on physical performance, such as aerobic and anaerobic power, is mixed. Some evidence suggests that protein supplementation may accelerate gains in both aerobic and anaerobic power when the training stimulus is adequate . However, in concurrent resistance and endurance training, protein supplementation enhances muscle mass and strength but does not improve whole-body aerobic capacity (VO2max) . In older adults, the effect of protein supplementation on physical performance measures like gait speed and chair-rise ability is generally inconclusive or minimal 67.
Protein Supplementation and Body Composition
Protein supplementation can positively affect body composition by increasing lean mass and reducing fat mass, particularly after bariatric surgery . However, it does not significantly change BMI or overall lean body mass in these populations . In athletes and active individuals, milk proteins and complete protein supplements are effective in promoting muscle protein synthesis, lean mass, and exercise recovery .
Protein Supplementation, Appetite, and Energy Intake
Concerns about protein supplementation suppressing appetite and reducing energy intake in older adults are largely unfounded. While acute protein supplementation may temporarily suppress appetite, it does not reduce total daily energy intake in the long term, making it a viable strategy to increase protein intake without compromising overall nutrition in healthy older adults .
Conclusion
Protein supplementation is most effective for enhancing muscle mass and strength when combined with adequate resistance training, especially in younger and resistance-trained individuals. Its benefits for older adults are more limited, particularly when habitual protein intake is already sufficient. The type of protein and the context of use (e.g., post-surgery, athletic training) can influence outcomes, but overall, protein supplementation is a valuable tool for supporting muscle health and body composition when paired with appropriate exercise.
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