Protein is the most important macronutrient for body composition, immune function, tissue repair, and many people’s most misunderstood dietary target. The simple question “how much protein do I need?” has a significantly different answer depending on your age, activity level, health status, and goals.
The Reference Nutrient Intake vs Optimal Intake
The UK Reference Nutrient Intake (RNI) for protein is 0.75g per kg of body weight per day — the amount needed to prevent deficiency in 97.5% of the population. A sedentary 70kg adult needs approximately 53g daily at minimum. However, optimal protein intake for health and body composition significantly exceeds the RNI. The international PROT-AGE and ESCEO guidelines, representing the most recent expert consensus, recommend 1.0–1.2g/kg/day for healthy older adults, and 1.2–1.5g for those with acute or chronic illness. For muscle building and preservation in active adults, 1.6–2.2g/kg is the evidence-based range.
Protein at Different Life Stages
Young adults (18–40): 1.6–2.2g/kg for active individuals aiming to build or maintain muscle. Even sedentary young adults benefit from 1.0–1.2g/kg for satiety, immune function and metabolic health. Pregnant women: protein needs increase by approximately 10g/day in the first trimester and 25–30g/day in the second and third — prioritising high-quality complete proteins (animal or combined plant sources). Older adults (over 60): this is where the RNI most significantly underserves. Sarcopenia (age-related muscle loss) accelerates from 60+, and resistance to protein’s muscle-building signal (anabolic resistance) increases with age — older adults need more protein, not less, to maintain muscle mass. 1.2–1.6g/kg, distributed across meals with at least 25–30g per meal (sufficient to trigger maximum muscle protein synthesis at the meal level), is the evidence-based target.
Protein Quality and Completeness
Complete proteins contain all nine essential amino acids in adequate quantities: all animal proteins (meat, fish, eggs, dairy) and soy are complete. Most plant proteins are “incomplete” — limited in one or more essential amino acids. This doesn’t mean plant protein is inadequate, but it does mean variety and combination matters: rice + beans, bread + hummus, lentils + rice — traditional combinations across cultures that provide complementary amino acid profiles. Leucine content specifically triggers muscle protein synthesis — higher in animal proteins (whey particularly) and important for older adults.
Frequently Asked Questions About Protein
Is there a maximum protein the body can use?
The body doesn’t “waste” protein by excreting it — excess protein above needs is oxidised for energy (less efficiently than carbohydrate). At very high intakes (above ~2.2g/kg in trained individuals), additional protein provides diminishing muscle-building returns. The practical limit for most people is not protein quantity but variety and food quality.
Does high protein damage kidneys?
In people with healthy kidneys, high protein diets are safe. The concern about protein and kidneys arises from the fact that people with existing kidney disease should restrict dietary protein (to reduce filtration burden). In healthy individuals without kidney disease, protein intakes up to 2.5–3g/kg are not associated with kidney damage in any robust evidence.
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