Protein: How Much Do You Actually Need — and When Does It Matter?

Why the RDA Is Misleading

The Recommended Dietary Allowance for protein — 0.8 grams per kilogram of body weight per day — represents the minimum to prevent deficiency in sedentary adults, not the amount that optimises health, muscle maintenance, or recovery. For most adults, particularly those over 40 or physically active, the evidence supports substantially higher intakes.

What the Evidence Recommends

A 2017 meta-analysis in British Journal of Sports Medicine (Morton et al., 49 studies, 1,800 participants) found that resistance training combined with protein supplementation increased muscle mass and strength significantly — and that the response plateau occurred at approximately 1.62 g/kg/day. For a 75 kg person, that is about 120 grams of protein daily.

For older adults (60+), the picture is even more demanding. Muscle protein synthesis becomes less efficient with age — a phenomenon called "anabolic resistance." Research suggests older adults may need 1.6–2.2 g/kg/day to maintain muscle mass, making adequate protein one of the most important dietary variables for healthy ageing.

Protein Distribution Matters

Total daily protein is not the only variable. Distribution across meals appears to influence muscle protein synthesis independently of total intake. Studies show that spreading protein evenly across 3–4 meals (rather than consuming most at dinner) maximises 24-hour muscle protein synthesis rates.

A 2014 study by Areta et al. in the Journal of Physiology found that consuming 20g of protein every 3 hours was superior to 40g every 6 hours or 10g every 1.5 hours for stimulating muscle protein synthesis over a 12-hour recovery period.

The practical implication: include a meaningful protein source (25–40g) at breakfast, which most people under-dose. Eggs, Greek yoghurt, cottage cheese, and protein shakes all qualify.

Per-Meal Upper Limits

A persistent myth holds that the body can only absorb 20–30g of protein per meal. This conflates the rate of digestion with the upper limit of use. Larger protein doses are absorbed more slowly but are fully utilised. However, for the purpose of maximising muscle protein synthesis, doses beyond 40g per meal appear to offer diminishing returns in most contexts (though they do not go to waste — excess is oxidised).

Protein Source Quality

Protein quality depends on amino acid profile and digestibility. Animal proteins (meat, fish, eggs, dairy) are complete sources containing all nine essential amino acids. Plant proteins vary in completeness:

• Soy — complete protein, comparable to whey in some studies
• Leucine-rich sources — leucine is the amino acid most responsible for triggering muscle protein synthesis; it is abundant in dairy (especially whey), eggs, and soy
• Combining plant sources — mixing legumes with grains provides complementary amino acid profiles

Protein and Satiety

Protein is the most satiating macronutrient. It stimulates the release of GLP-1 and PYY (satiety hormones) and suppresses ghrelin (the hunger hormone) more effectively than carbohydrates or fats. Studies show that increasing protein from 15% to 30% of total calories reduces ad libitum calorie intake by approximately 441 kcal per day — without any explicit calorie restriction instruction.

The practical takeaway: if you have one dietary lever to pull for body composition and health, making protein intake adequate and consistent is likely to have the broadest impact.