Dietary Protein: How Much, From Where, and Why It Matters

What Protein Does in Your Body

Protein is one of three macronutrients your body cannot function without. It supplies the amino acids your cells use to build and repair muscle tissue, produce enzymes and hormones, support immune function, and transport oxygen through the bloodstream. Unlike carbohydrates and fat, your body has no dedicated storage depot for protein — so a steady daily supply matters. For a plain-language primer on all three macronutrients together, see Macronutrients at a Glance.

Of the 20 amino acids proteins are built from, nine are considered essential — meaning your body cannot synthesize them and must obtain them through food. The other 11 are nonessential, though some become conditionally essential during illness or stress.

How Much Protein Do You Actually Need?

The commonly cited baseline — the Recommended Dietary Allowance (RDA) — is 0.8 grams of protein per kilogram of body weight per day for healthy adults. For a 150-pound (68 kg) person, that works out to roughly 54 grams daily. However, the RDA reflects the minimum needed to prevent deficiency, not necessarily the amount that optimizes health.

Current research in sports nutrition and healthy aging suggests higher intakes — often cited in the range of 1.2–2.0 g/kg/day — may better support muscle maintenance in older adults and recovery in active individuals. These figures are general educational reference points; individual needs vary meaningfully based on age, health status, activity level, and total calorie intake. Consult a registered dietitian if you want guidance tailored to your circumstances.

This article provides general nutrition information and is not a substitute for personalized advice from a qualified healthcare professional.

Protein Quality: Not All Sources Are Equal

Beyond quantity, protein quality matters. Quality is determined by two factors: whether a food contains all nine essential amino acids, and how well your body can actually absorb and use them.

• Complete proteins supply all nine essential amino acids. Animal sources — eggs, dairy, meat, poultry, and fish — are classic examples. So are a handful of plant foods: quinoa, soy, and buckwheat.
• Incomplete proteins are low in one or more essential amino acids. Most legumes, grains, nuts, and vegetables fall here. Pairing complementary plant proteins (e.g., rice and beans) across the course of the day addresses this gap without requiring strict meal-by-meal combining.

Digestibility also varies. Scoring systems like PDCAAS (Protein Digestibility-Corrected Amino Acid Score) and the newer DIAAS (Digestible Indispensable Amino Acid Score) attempt to capture both factors in a single number, helping researchers compare sources. For a deeper side-by-side look at how animal and plant proteins compare on these dimensions, see Plant-Based Proteins vs. Animal Proteins.

Practical Sources Across Eating Patterns

Protein-rich foods fit nearly every dietary framework, from omnivore to fully plant-based:

• Animal sources: Eggs, Greek yogurt, cottage cheese, canned tuna, chicken breast, and lean beef tend to be high in protein relative to calories and score well on digestibility measures.
• Plant sources: Lentils, black beans, edamame, tofu, tempeh, and seitan offer substantial protein along with fiber and micronutrients that animal foods largely lack.
• Mixed options: Dairy products like milk and cheese, or eggs, occupy a middle ground and fit flexitarian approaches well.

Variety is a practical asset: spreading protein intake across multiple food types tends to fill amino acid gaps naturally and supports gut microbiome diversity. Protein Sources Side by Side walks through the trade-offs in more detail if you want to evaluate specific options.