Protein
Protein is made of amino acids, the building blocks your body uses to repair muscle, make hormones and enzymes, and grow and maintain every tissue you have.
On this page
Why protein matters
- Builds and repairs muscle. Lifting creates the signal; protein supplies the amino acids that muscle protein synthesis uses to rebuild fibres bigger and stronger.
- Keeps you full. Protein is the most filling macronutrient, which makes a calorie deficit far easier to stick to.
- Costs more to digest. Around 20–30% of the calories in protein are used up digesting it, against 5–10% for carbs and 0–3% for fat1.
- Runs your body. Enzymes, many hormones, antibodies and the transporters in your blood are all proteins.
Protein has 4 kcal per gram, the same as carbohydrate. Of its 20 amino acids, 9 are essential: your body can't make them, so they have to come from food.
How much protein you need
| Who | Grams per kg of body weight a day | For a 75 kg person |
|---|---|---|
| Most adults (UK reference nutrient intake)2 | 0.75 | about 56 g |
| Lifting to build muscle34 | 1.6–2.2 | 120–165 g |
| Cutting (in a calorie deficit) while lifting56 | 2.0–2.4 | 150–180 g |
| Adults over 657 | 1.0–1.2 (1.2+ if active) | 75–90 g |
Research spotlight
Across 49 trials and 1,863 people, extra protein boosted the muscle and strength gains from resistance training, and the benefit levelled off at about 1.6 g per kg of body weight a day.
Spread it through the day: about 0.4 g per kg in each of 3–5 meals is a good pattern for muscle building8. See Protein timing for more.
Best food sources of protein
| Food | Per 100 g | Per serving |
|---|---|---|
| Whey protein powder (varies by brand) | 78 g | 23.4 g30 g scoop |
| Chicken breast, cooked, no skin | 31 g | 46.5 g1 breast (150 g) |
| Beef mince, 5% fat, cooked | 27 g | 33.8 g125 g |
| Tuna, canned in spring water, drained | 25 g | 27.5 g1 can (110 g drained) |
| Cod, baked | 23 g | 32.2 g1 fillet (140 g) |
| Peanut butter | 22.5 g | 7.2 g2 tbsp (32 g) |
| Salmon, farmed, cooked | 22 g | 26.4 g1 fillet (120 g) |
| Tempeh | 20 g | 20 g100 g |
| Tofu, firm (varies by brand) | 13 g | 15.6 g120 g |
| Oats, dry | 13 g | 5.2 g40 g |
| Eggs, whole | 12.6 g | 15.1 g2 large eggs (120 g) |
| Edamame beans, cooked | 12 g | 9.6 g80 g |
| Skyr | 11 g | 16.5 g150 g pot |
| Cottage cheese | 11 g | 16.5 g150 g |
| Greek-style yoghurt, 0% fat | 10 g | 17 g170 g pot |
| Lentils, boiled | 9 g | 13.5 g150 g |
| Chickpeas, canned, drained | 7 g | 8.4 g120 g |
| Milk, semi-skimmed | 3.5 gper 100 ml | 8.8 gGlass (250 ml) |
Complete proteins have all 9 essential amino acids in useful amounts: meat, fish, eggs, dairy, soya and quinoa. Most other plant proteins are low in one or two, but eating a mix across the day (beans and rice, hummus and wholemeal pitta) covers them11. With enough total protein, plant-based lifters gain muscle as well as meat eaters do12.
Deficiency signs and common myths
Protein deficiency is rare in the UK. When intake is genuinely too low, it shows up as muscle loss and weakness, slow healing and, in severe cases, swelling (oedema).
MythYou can only absorb 30 g of protein in one meal.
FactYour gut absorbs all of it. One carefully controlled study found a 100 g dose built muscle for longer than 25 g13. Spreading protein out is still a good habit, but a big dinner isn't wasted.
MythHigh-protein diets damage your kidneys.
FactIn healthy people, higher protein intakes haven't been shown to harm kidney function14. If you have kidney disease, follow your doctor's advice.
MythYou need protein shakes to build muscle.
FactShakes are just convenient food. Whole foods work just as well; use powder when it helps you hit your number.
Questions people ask
Is it possible to eat too much protein?
For healthy adults, intakes up to around 2.2 g per kg are well studied. Going far higher mostly just replaces carbs and fats you might rather eat, and costs more.
Should I count protein from bread and pasta?
Yes. Every gram counts towards your daily total, even if plant proteins are a little less efficient for muscle building than animal ones.
Do I need more protein on rest days?
Keep it roughly the same. Muscle rebuilding carries on for a day or two after training.
Track this in NutriLog
See your protein every day
Log meals by scanning barcodes and see protein against a target set for your goal and body weight.
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References
- Westerterp KR. Diet induced thermogenesis. Nutr Metab (Lond). 2004;1(1):5. doi:10.1186/1743-7075-1-5
- Department of Health. Dietary Reference Values for Food Energy and Nutrients for the United Kingdom (Report on Health and Social Subjects 41). HMSO, London, 1991.
- Morton RW, Murphy KT, McKellar SR, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52(6):376-384. doi:10.1136/bjsports-2017-097608
- Jäger R, Kerksick CM, Campbell BI, et al. International Society of Sports Nutrition position stand: protein and exercise. J Int Soc Sports Nutr. 2017;14:20. doi:10.1186/s12970-017-0177-8
- Helms ER, Aragon AA, Fitschen PJ. Evidence-based recommendations for natural bodybuilding contest preparation: nutrition and supplementation. J Int Soc Sports Nutr. 2014;11:20. doi:10.1186/1550-2783-11-20
- Longland TM, Oikawa SY, Mitchell CJ, Devries MC, Phillips SM. Higher compared with lower dietary protein during an energy deficit combined with intense exercise promotes greater lean mass gain and fat mass loss: a randomized trial. Am J Clin Nutr. 2016;103(3):738-746. doi:10.3945/ajcn.115.119339
- Bauer J, Biolo G, Cederholm T, et al. Evidence-based recommendations for optimal dietary protein intake in older people: a position paper from the PROT-AGE Study Group. J Am Med Dir Assoc. 2013;14(8):542-559. doi:10.1016/j.jamda.2013.05.021
- Schoenfeld BJ, Aragon AA. How much protein can the body use in a single meal for muscle-building? Implications for daily protein distribution. J Int Soc Sports Nutr. 2018;15:10. doi:10.1186/s12970-018-0215-1
- Public Health England. McCance and Widdowson's The Composition of Foods Integrated Dataset (CoFID). GOV.UK, 2021.
- U.S. Department of Agriculture, Agricultural Research Service. FoodData Central. fdc.nal.usda.gov.
- NHS. The vegan diet. nhs.uk.
- Hevia-Larraín V, Gualano B, Longobardi I, et al. High-protein plant-based diet versus a protein-matched omnivorous diet to support resistance training adaptations: a comparison between habitual vegans and omnivores. Sports Med. 2021;51(6):1317-1330. doi:10.1007/s40279-021-01434-9
- Trommelen J, van Lieshout GAA, Nyakayiru J, et al. The anabolic response to protein ingestion during recovery from exercise has no upper limit in magnitude and duration in vivo in humans. Cell Rep Med. 2023;4(12):101324. doi:10.1016/j.xcrm.2023.101324
- Devries MC, Sithamparapillai A, Brimble KS, et al. Changes in kidney function do not differ between healthy adults consuming higher- compared with lower- or normal-protein diets: a systematic review and meta-analysis. J Nutr. 2018;148(11):1760-1775. doi:10.1093/jn/nxy197