Protein basics
How much protein you need, and why
The numbers behind a daily target: what the official recommendations say, where they came from, how to turn them into grams, and whether a high intake is anything to worry about.
11 articles
- Can your body only absorb 30 g of protein at a time?No. Absorption is close to complete at any normal meal size; the small intestine is not the bottleneck. The 20 to 30 g figure comes from studies of how much muscle building a single dose triggers, which is a different question. Protein above that is still digested and still used, just not for that one purpose.
Complete and incomplete protein, and what it means for youA complete protein carries all nine essential amino acids in amounts a human can use. Meat, fish, eggs, dairy and soy do. Most other plant foods are short in one, usually lysine in grains and methionine in legumes. The practical effect is smaller than the wording suggests: variety across a day covers it.
Does it matter when you eat protein?Far less than the daily total. The post-exercise window is hours wide rather than minutes, and the sports nutrition position stands say total intake dominates. What does appear to help is spreading protein across meals instead of loading most of it into dinner, and that effect grows with age.
Essential amino acids, and why leucine gets namedNine of the twenty amino acids cannot be made by the body and must come from food: histidine, isoleucine, leucine, lysine, methionine, phenylalanine, threonine, tryptophan and valine. Animal foods carry all nine in useful amounts. Most plant foods are short in one, which matters over a day rather than at a meal.
How protein quality is scored, and when the score mattersProtein quality measures how much of a source your body can actually use, combining its amino acid profile with how completely it is digested. Two scoring systems are in use: PDCAAS, which is older and caps at 1.0, and DIAAS, which measures digestion further down the gut and separates sources the older score treated as equal.
How to read protein on a food labelCheck which basis the figure uses before anything else: per 100 g is for comparing products, per serving is for planning your day, and the serving on the pack is often not the amount you eat. Front-of-pack claims like high in protein are legally defined by the share of energy from protein, not by the grams.
Is the protein RDA too low?It answers a narrower question than most people think. The 0.8 g/kg figure is the intake at which almost nobody loses body nitrogen, derived from balance studies, so it is a floor for avoiding deficiency. A newer method puts the requirement higher, and the expert groups already recommend more for older adults and for people training.
Is too much protein bad for you?For healthy adults with normal kidney function there is no established upper limit. The Institute of Medicine set no Tolerable Upper Intake Level for protein, and a 2018 meta-analysis of 28 trials found kidney function changed no differently on higher protein intakes than on lower ones. Reduced kidney function is the real exception, and that target belongs with a clinician.
What not eating enough protein actually looks likeMostly you do not, which is the difficulty. Genuine protein deficiency is rare where food is plentiful and produces clear clinical signs. Falling short of a useful target is ordinary and produces almost nothing you would notice day to day: muscle is lost slowly, over months, while the scale can stay exactly where it was.
What protein actually does in your bodyProtein supplies amino acids, which your body uses as building material: muscle, skin, hair, enzymes, antibodies, and the proteins that carry things around your blood. Unlike fat and carbohydrate it is not stored for later, so the supply has to arrive roughly daily. That is the reason protein is tracked as a number per day rather than per week.
How much protein do you need per day?The official adult minimum is 0.8 grams of protein per kilogram of body weight per day, which is about 56 g for a 70 kg person. That figure prevents deficiency. Research groups recommend 1.0 to 1.2 g/kg for adults over 65, and higher again during weight loss or regular training.