Protein studies, tips and resources
Every tip and study on this site, each in one line you can pass on. Tap Copy and it goes in a message with its link.
Tips to pass on
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If you can, get your protein from food first. One protein food in every meal gets most adults to their range with no powder.
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Most adults need 1.2 to 1.6 g of protein per kg a day, about 100 to 130 g at 180 lb, the US range since January 2026.
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US adults eat about 15 g of protein at breakfast and 32 g at dinner. Breakfast is where the missing grams are easiest to add.
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Aim for about 0.4 g of protein per kg at each meal, about 30 g at 165 lb.
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Shrimp, canned tuna, cod, turkey and egg whites all have more protein per calorie than chicken breast.
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Peanut butter has 3.7 g of protein per 100 calories, less than a plain bagel at 4.0.
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Protein past 30 g in a meal isn't wasted. In a 2023 trial, 100 g at once kept muscle building going for more than 12 hours.
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Across 23 studies, protein timed around a workout made no difference once the day's total was counted.
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25 g of protein costs about 43 cents from dried beans and 77 cents from eggs at US average prices.
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Rice and beans fill each other's amino acid gaps. Peanut butter on whole wheat doesn't, since both run short on lysine.
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4 oz of raw chicken breast is about 3 oz cooked, and both carry about 25 g of protein.
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Protein needs a job. Lift at least twice a week, the US activity guidelines' minimum.
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A gram of protein from a shake counts like a gram from food. Keep powder for the gaps, and not every day.
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With kidney disease, your doctor sets your protein number, not a calculator.
The studies
How much a day
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2018. Extra protein added lean mass on top of lifting, and the gains leveled off near 1.6 g per kg a day.
Morton and others, 49 trials, 1,863 people who lifted
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2022. More protein gave a small extra gain in lean mass, and in adults under 65 who lifted it showed at 1.6 g per kg or more.
Nunes and others, 74 trials
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2014. Lean lifters dieting hard need about 2.3 to 3.1 g per kg of lean mass to hold their muscle.
Helms and others, a review of 6 studies of trained lifters
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2016. On a hard diet with training 6 days a week, 2.4 g per kg gained 1.2 kg of lean mass and lost 4.8 kg of fat, against 0.1 and 3.5 kg on 1.2 g.
Longland and others, 40 young men, 4 weeks
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2013. Adults over 65 should eat at least 1.0 to 1.2 g of protein per kg a day.
Bauer and others, the PROT-AGE study group
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2023. The old minimum of 0.8 g per kg wasn't enough for them to break even on protein.
Bartholomae and Johnston, minimally active vegan men
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2026. The new 1.2 to 1.6 g per kg range rests mostly on trials in adults losing weight, which the authors say isn't enough evidence.
Pasiakos and others, a commentary
Per meal and timing
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2015. Muscle building after one meal leveled off at about 0.24 g per kg in men around 22 and 0.40 in men around 71.
Moore and others, pooled lab studies
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2013. Over 12 hours, four doses of 20 g built more muscle protein than eight of 10 g or two of 40 g.
Areta and others, 24 trained young men
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2023. 100 g of protein after a workout kept muscle building going for more than 12 hours, longer and stronger than 25 g.
Trommelen and others, 36 young men
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2022. Protein spread evenly over the day built no more muscle protein than a day skewed to dinner.
Justesen and others, 24 adults aged 65 to 80
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2013. Protein timed around a workout made no difference to muscle once the day's total was counted.
Schoenfeld, Aragon and Krieger, 23 studies
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2023. US adults eat 19% of their protein at breakfast, 27% at lunch, 42% at dinner and 13% in snacks, about 77 g a day.
USDA, What We Eat in America, 2021 to 2023
Safety
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2018. Higher protein didn't harm kidney function, though most of the trials were short.
Devries and others, 28 studies, 1,358 healthy adults
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2025. On a GLP-1, eat the protein first at each meal and lift, and avoid more than 2 g per kg a day for long periods.
Mozaffarian and others, a joint advisory of four US societies
Plants, quality and powder
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2018. Leucine was 11.0% of whey protein and 7.1% of plant proteins on average, and soy, pea and brown rice still met the adult pattern.
Gorissen and others, protein isolates
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2020. Casein, pork and egg scored excellent, soy and whey high quality, and pea, oat, hemp, wheat, rice and corn lower.
Herreman and others, a review of DIAAS scores
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2025. More than two thirds had more lead in a serving than a cautious daily level, and plant ones averaged about nine times dairy's.
Consumer Reports, 23 protein powders and shakes
Resources
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Dietary Guidelines for Americans, 2025 to 2030 The US range of 1.2 to 1.6 g of protein per kg a day, and protein foods at every meal.
US Department of Agriculture and Department of Health and Human Services
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Dietary Reference Intakes The RDAs by age and life stage, 0.8 g per kg a day for adults.
National Academies
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FoodData Central The protein in almost any food, the database behind every number on this site.
US Department of Agriculture
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Daily Value on the Nutrition and Supplement Facts labels Why food labels count 50 g of protein as a day.
US Food and Drug Administration
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Questions and Answers on Dietary Supplements Why nobody checks a protein powder before it's sold.
US Food and Drug Administration
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Why is third-party certification important for dietary supplements? What a seal on a tub of powder means, and what it doesn't.
Operation Supplement Safety, US Department of Defense
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Adult activity: an overview At least 2 days a week of muscle work for every adult.
CDC
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Sports Supplements For teens: most get the protein they need from food.
Nemours TeensHealth
