macronutrientsprotein

Protein is a macronutrient required in larger amounts by the body. It is composed of amino acids, some of which are essential because the body cannot synthesize them. In the diet, protein supports tissue growth and repair, forms enzymes and hormones, contributes to immune function, and can be used for energy when other sources are insufficient. Unlike fats and carbohydrates, protein is not primarily stored for energy; its main role is structural and functional.

Recommended intake for protein varies by age, sex, and activity. For healthy adults, a common guideline is about 0.8 grams per kilogram of body weight per day. Athletes and people aiming to preserve or build muscle often require higher intakes, roughly 1.2–2.0 g/kg/day, and older adults may benefit from a similar or higher range. Protein needs should be distributed across meals rather than concentrated in a single meal.

Protein quality depends on amino acid composition and digestibility. Essential amino acids must be supplied by the diet; complete protein sources provide all essential amino acids in sufficient amounts. Animal products typically offer complete proteins, while many plant sources are limiting in one or more essential amino acids; combinations such as grains with legumes can provide a complete profile. Protein quality can be summarized by metrics such as PDCAAS or DIAAS, used in nutrition labeling and dietary planning.

Daily protein intake should consider energy balance and overall diet. Consuming adequate protein supports muscle protein synthesis, especially after resistance exercise, and helps maintain lean mass during weight loss. Excessive protein intake beyond needs has limited additional benefit for most people and can displace other important nutrients.

Common dietary sources include meat, fish, eggs, dairy, legumes, nuts, seeds, and some grains. Plant-based diets can meet protein needs with careful planning. Individuals with kidney disease or other conditions should consult healthcare professionals to tailor protein intake.