Protein supplement

A meta-study found that in the first few weeks of strength training with untrained individuals, changes in lean body mass and muscle strength during the initial weeks of strength training are not influenced by the protein supplementation, but after the first few weeks, protein supplementation “may promote muscle hypertrophy and enhance gains in muscle strength in both untrained and trained individuals”[1] Also, whey-protein supplementation in overweight individuals may reduce the body weight, total fat mass and risk factors for cardiovascular diseases.[2]

When combined with strength training, protein supplementation promotes greater gains in lean body mass and muscle strength as the intensity, frequency, and duration of strength training increases.[1] It increases the muscles' strength and size, during prolonged strength training in healthy adults.[3] A meta-study concluded that intake of protein supplements higher than around 1.6 g/kg/day do not further improve the gains in FFM (fat free mass)[3] “at least for younger individuals”,[3] although it states that “it may be prudent to recommend ~2.2 g protein/kg/d for those seeking to maximise resistance training-induced gains in FFM”.[3]

However, aging reduces the effect of protein intake, and older adults need 1.2 g/kg/day (over 1.2 g/kg/day if they are doing strength training), with some researchers recommending 2.0 g/kg/day.[4] If they have acute or chronic diseases they need 1.2–1.5 g/kg body weight/day.[5] “Older people with severe kidney disease (ie, estimated GFR <30 mL/min/1.73m2), but who are not on dialysis, are an exception to this rule; these individuals may need to limit protein intake.”.[6] Increased resistance training also helps balance aging's negative effect on muscle mass.[3]

Past studies propose that spreading protein intake through the day (with a maximum of 30g at a time) achieves maximal total stimulation of muscle protein synthesis.[7][8] However, recent studies suggest that protein intake for muscle gain can taken either throughout the day or at one time, if that is more convenient.[9]

There is no evidence supporting specific pre/post-workout timing for protein-supplement intakes, despite the widely held belief that pre- or post-workout protein supplementation would be more effective.[10]

Nutritional status can be altered in people living with chronic kidney disease (CKD). There is moderate-certainty evidence that regular consumption of oral protein-based nutritional supplements may increase serum albumin, a protein that can be lower in people with CKD, due to increased loss in urine and malnutrition. Improvements in albumin following protein supplementation may be greater in those who require hemodialysis or who are malnourished.[11] Pre-albumin levels and mid-arm circumference measurements may also be increased following supplementation, though the certainty of evidence is low.[11] Although these indicate possible improvements in nutritional status, it is unclear whether protein supplements affect quality of life, life expectancy, inflammation or body composition.[11]