Your muscles are broken down and rebuilt from protein every single day. Most adults eat enough to avoid deficiency, but not enough to build or keep muscle, especially if they train or are over 50.
Strong evidenceProtein is made of 20 building blocks called amino acids. Nine of them are 'essential': your body can't make them, so they must come from food. One, leucine, acts like a switch that tells muscle to start building.
Muscle is always being broken down and rebuilt. Strength training plus enough protein tips the balance toward building. After about 50, muscles respond less to the same meal (anabolic resistance), so older adults need more protein per meal to get the same effect.
The total you eat in a day matters most. Spreading it across three or four meals is a practical way to reach it, and a newer study shows big single meals still work, just over a longer time.
The same 90 g of protein. Spread evenly, it switches on muscle building three times instead of once (Mamerow 2014).
Eggs, fish, dairy, beans, tofu, meat and lentils supply amino acids.
Your gut breaks protein into amino acids, which enter your blood.
Leucine flips the muscle-building switch for several hours.
Lifting tells your body where to put the new protein.
0.8 g/kg is the official minimum to avoid deficiency. Expert groups suggest 1.0–1.2 g/kg for over-65s and 1.2–1.6 g/kg when strength training.
49 trials, 1,863 adults
Protein supplements added to strength training boosted muscle and strength gains. The benefit levelled off around 1.6 g per kg of body weight a day.
Find on PubMed ↗36 young men
A 100 g protein meal after exercise built more muscle, for longer (12+ hours), than 25 g. The idea that the body 'wastes' anything over 30 g was wrong.
Find on PubMed ↗8 adults, crossover
Spreading 90 g of protein evenly over three meals gave 25% more muscle building over 24 hours than eating most of it at dinner.
Find on PubMed ↗International expert group
Recommended 1.0–1.2 g/kg a day for adults over 65, and more for those who are ill or very active, to slow muscle loss.
Find on PubMed ↗74 trials
Higher protein intake modestly increased lean mass, with the biggest effect when combined with strength training.
Find on PubMed ↗38 young adults, 10 weeks
A fully plant-based, high-protein diet built the same amount of muscle with training as a diet with meat and dairy.
Find on PubMed ↗You don't need shakes. Plan a protein food into every meal first.
About a palm and a half of protein food. Older adults should aim for the top of that range.
Swap toast or cereal for eggs, Greek yoghurt, skyr, cottage cheese or tofu.
Protein without training mostly gets burned for energy. Two or three strength sessions a week make it count.
Fish, eggs, dairy, poultry, beans, lentils, tofu and tempeh. Limit processed meat.
Plant proteins have a little less leucine. Add 10–20% or combine grains with beans.
About 40 g of slow protein (cottage cheese, yoghurt) before bed boosted overnight muscle building in trials.
✕ MythYour body can only use 30 g of protein at once.
✓ FactA 2023 trial found 100 g kept building muscle for longer. The total over the day matters more than the size of each meal.
✕ MythHigh protein damages healthy kidneys.
✓ FactStudies in people with healthy kidneys haven't shown harm. If you have kidney disease, follow your doctor's advice.
✕ MythYou can't build muscle on plants.
✓ FactA 10-week trial showed a vegan diet built the same muscle as an omnivore diet when protein was high enough.
✕ MythMore protein is always better.
✓ FactGains flatten around 1.6 g/kg. Beyond that it's just extra calories.
No. It's a convenient food, not magic. Pick one with third-party testing if you use it.
Either works. Eating protein within a few hours either side of training is plenty.
Put protein first on the plate, use milk-based drinks and snacks, and spread intake across the day.