Protein builds and repairs tissue, produces enzymes and hormones, and supports immune function. The RDA of 0.8 g per kg body weight prevents deficiency in sedentary adults — but active people, older adults, and those losing weight often benefit from significantly more.
Targets by Goal
Sedentary adults: 0.8–1.0 g/kg. Regular exercisers: 1.2–1.6 g/kg. Strength athletes and heavy lifters: 1.6–2.2 g/kg. Adults over 65: 1.2–1.5 g/kg to counter age-related muscle loss (sarcopenia). During fat loss, higher protein (1.6–2.4 g/kg) preserves lean mass in a calorie deficit.
Best Sources
Complete proteins contain all nine essential amino acids: meat, fish, eggs, dairy, soy, and quinoa. Combining legumes with grains (rice and beans) provides complete profiles. Whey and casein supplements are convenient but not superior to whole food when total intake is equal.
Timing and Distribution
Total daily intake matters most. Distributing 25–40 g per meal optimizes muscle protein synthesis — the process of building new muscle tissue. A post-workout shake helps if your next meal is hours away, but the "anabolic window" is wider than gym culture claims (several hours).
Myths
High protein does not damage healthy kidneys — concern applies only to existing renal disease. More than ~2.2 g/kg shows diminishing returns for muscle gain. Excess protein is oxidized for energy or stored as fat, not magically converted to extra muscle.