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 evidenceUpdated Oct 2026 · 4 new studiesProtein 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 ↗US guidelines now suggest 1.2 to 1.6 g of protein per kg of body weight, well above the old 0.8 g. But a new trial shows extra protein alone does not make older adults stronger, and population data favour plant protein for adult lifespan.
Every study added to this page since January 2025. Green rings are the strongest evidence: large trials or meta-analyses.
Dietary Guidelines for Americans 2025–2030. The formal minimum (RDA) is still 0.8 g/kg, but the guidelines now suggest 1.2 to 1.6 g/kg.
national guideline
The suggested protein intake rose from 0.8 g to 1.2 to 1.6 g per kg of body weight a day, from both animal and plant sources. The formal RDA of 0.8 g per kg has not changed.
141 adults aged 65+, 24 weeks
Daily whey protein capsules did not improve muscle strength compared with placebo, even though the body showed signs of being primed to build muscle. Protein alone, without training, did little.
1,868 adults aged 60+ with two or more long-term conditions, 13 years
Those in the top third for protein (average intake was about 1.2 g per kg) had a 34% lower risk of becoming frail. Plant protein was linked to a lower risk of death, and fish protein to less frailty.
food supply data from 101 countries, 1961 to 2018
Countries with more plant protein in their food supply had longer adult life expectancy, while more animal protein was linked to lower deaths in young children. This is population data, so it shows links, not cause.
Aim for about 1.2 to 1.6 g of protein per kg of body weight a day, spread over meals, with plenty from plants and fish. But pair it with strength training: protein on its own didn't make older adults stronger.
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.
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Active adults and older people benefit from about 1.2–1.6 g of protein per kg of body weight a day.
Active adults and older people benefit from about 1.2–1.6 g of protein per kg of body weight a day.
The basic 0.8 g/kg recommendation prevents deficiency; strength gains in trials plateau around 1.6 g/kg.
Your body can only use 30 g of protein from one meal.
Your body can only use 30 g of protein from one meal.
A 2023 trial (Trommelen) found the body kept building muscle for 12 hours after 100 g. Spreading it out is still sensible.
High-protein diets damage healthy kidneys.
High-protein diets damage healthy kidneys.
In people with healthy kidneys, studies haven't shown harm. People with kidney disease should follow medical advice.
Older adults need more protein per meal to trigger muscle building.
Older adults need more protein per meal to trigger muscle building.
Ageing muscle responds less ('anabolic resistance'), so around 30–40 g in a meal works better than 20 g.
Plant protein is incomplete and can't build muscle.
Plant protein is incomplete and can't build muscle.
Single plants can be low in some amino acids, but mixing sources (beans plus grains) or eating a bit more works well.
Protein keeps you fuller than the same calories of carbs or fat.
Protein keeps you fuller than the same calories of carbs or fat.
It's the most filling macronutrient, which helps with weight control.
You need protein shakes to build muscle.
You need protein shakes to build muscle.
They're convenient, not essential. Food works just as well if you get enough total protein.
Leucine is a key amino acid for turning on muscle building.
Leucine is a key amino acid for turning on muscle building.
Whey, eggs, meat and fish are rich in it; soy is a good plant source.
You must eat protein within 30 minutes after training.
You must eat protein within 30 minutes after training.
The 'anabolic window' is much wider; total daily protein matters far more.
Eating enough protein while losing weight helps protect muscle.
Eating enough protein while losing weight helps protect muscle.
Trials show higher protein plus strength training keeps more lean mass during a calorie deficit.
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