Protein, Muscle, and the Ageing Body: How Much Do You Actually Need?
Sarcopenia — age-related muscle loss — is one of the strongest predictors of early mortality. The good news: it's largely preventable. The bad news: most people are eating far too little protein to prevent it.
The sarcopenia problem
After the age of 30, adults lose approximately 3–8% of muscle mass per decade. After 60, that rate accelerates. By 80, many people have lost 30–40% of the muscle mass they had at their peak. This process — sarcopenia — is not cosmetic. Muscle mass is one of the strongest predictors of all-cause mortality, independent of other factors.
Grip strength, a rough proxy for overall musculoskeletal health, predicts cardiovascular mortality better than blood pressure in several large cohort studies. Muscle is not just for aesthetics or athletic performance — it is metabolically active tissue that regulates glucose disposal, produces myokines with anti-inflammatory and neuroprotective effects, and serves as an amino acid reservoir during illness.
Muscle is the organ of longevity. Everything else — sleep, nutrition, stress — feeds into how well you build and maintain it.
The protein intake problem
The Recommended Dietary Allowance (RDA) for protein in most Western countries is 0.8g per kilogram of bodyweight per day. This figure represents the minimum to prevent deficiency — not the optimal intake for maintaining muscle mass, supporting immune function, or ageing well.
The emerging research consensus places the optimal protein intake for adults over 40 at 1.6–2.2g per kilogram of bodyweight per day — roughly double the RDA. For a 75kg person, that's 120–165g of protein daily.
Why older adults need more protein
- Anabolic resistance: Ageing muscle becomes less sensitive to the anabolic signal of dietary protein. Higher doses are needed to stimulate the same protein synthesis response.
- Reduced digestive efficiency: Gastric acid production declines with age, impairing protein digestion and amino acid absorption.
- Competing demands: Immune function, tissue repair, and enzyme production all compete for dietary amino acids.
Leucine and the muscle protein synthesis threshold
Not all protein is equal. The key driver of muscle protein synthesis (MPS) is leucine, a branched-chain amino acid that acts as an anabolic trigger. Each meal needs to contain approximately 2.5–3g of leucine to maximally stimulate MPS — roughly 30–40g of high-quality complete protein.
This has implications for meal distribution. Spreading protein evenly across 3–4 meals — rather than eating most of it at dinner — appears to produce meaningfully better muscle protein synthesis outcomes over 24 hours.
Practical protein targets
- Aim for 1.6–2.2g/kg bodyweight — skew toward the higher end if over 50
- Target 30–40g of complete protein per meal, 3–4 times daily
- Prioritise high-leucine sources: eggs, chicken, fish, dairy, beef
- Post-resistance-training protein (within 2 hours) is particularly effective
- Plant protein sources can work well but often require higher total intake to match leucine delivery
The evidence is unambiguous: most adults over 40 are significantly under-eating protein relative to what their muscle and metabolic health requires. Fixing this, combined with regular resistance training, is arguably the highest-ROI nutritional intervention available.