Protein: What It Does and Why It Matters

Protein is the macronutrient people ask about most and understand least. It is not only about muscle: amino acids from dietary protein are used to build enzymes, transport molecules, antibodies, skin, and connective tissue.

How much do you need?

Population reference intakes used by bodies such as EFSA and the NIH sit around 0.8 g per kilogram of body weight per day for healthy adults — a level intended to meet the needs of nearly everyone, not an optimum for every goal. Sports nutrition guidance typically suggests a higher range, roughly 1.2 to 2.0 g/kg, for people training regularly.

Protein quality

Quality reflects the amino acid profile and how well protein is digested. Animal sources — eggs, dairy, fish, meat — supply all essential amino acids in readily usable proportions. Most plant sources are lower in one or more essential amino acids, which is addressed easily by eating a variety of legumes, grains, nuts, and seeds across the day.

Practical sources

• Greek yogurt: roughly 10 g per 100 g, and an easy breakfast base.
• Eggs: about 6 g each, with choline, B12, and selenium alongside.
• Lentils: around 9 g per 100 g cooked, plus substantial fibre.
• Chicken breast and white fish: lean, high-protein staples.
• Tofu and tempeh: complete plant proteins that take on flavour well.

Distribution across the day

Most people load protein into the evening meal. Moving some of it to breakfast and lunch usually makes daily targets easier to reach and meals more satisfying — a bowl of yogurt with seeds, or eggs on wholegrain toast, changes a morning noticeably.

Is more always better?

There is a plateau. Beyond the ranges above, additional protein largely contributes energy rather than further benefit. For healthy adults, intakes within these ranges are considered well tolerated; people with kidney disease should follow individual medical advice.