Protein
Today
3-day window. Water-soluble and not stored, so a short run of days is the signal.
What it is
Protein is broken down into amino acids and rebuilt into muscle, enzymes, antibodies and hormones. Nine of those amino acids can't be made by the body at all, so they have to come from food. The official minimum is lower than most people expect — around 56 g a day for an adult man — but that figure is the amount needed to avoid losing tissue, not the amount that is best for building or keeping muscle. Spreading intake across meals works better than eating most of it at dinner.
Reference intake
Your daily target, personalised to your age and sex.
- RDA
- 56 gmale_19_plus
- Upper limit
- none established
What the evidence says
Wording reflects how strong the evidence actually is.
Preserves lean mass during weight loss
Increases muscle mass and strength gains from resistance training
May improves satiety and reduces spontaneous energy intake
May slows age-related muscle loss in older adults
May high intake damages healthy kidneys, though the evidence is thin
Deficiency
protein-energy malnutrition
Rare in high-income countries at the level of frank deficiency. Marginal intake is common in older adults, in people eating very low energy diets, and in some hospitalised populations.
Early signs
- loss of muscle mass and strength
- slow wound healing
- hair thinning and brittle nails
- frequent infections
- persistent fatigue
Higher risk
- older adults, who need more per meal to trigger the same response
- people in a sustained energy deficit
- people recovering from surgery, burns or serious illness
- poorly planned vegan diets with little legume or soy intake
- people with malabsorptive conditions
Excess
No upper limit has been set. Intakes well above the RDA are not associated with harm in people with normal kidney and liver function, though very high intakes displace other foods and can crowd out fibre and phytonutrients.
From supplements
- gastrointestinal discomfort from large single doses
- displacement of other foods, reducing dietary variety
- meaningful risk only where kidney or liver function is already impaired
At extreme doses
In existing chronic kidney disease, high protein intake accelerates decline in glomerular filtration and intake should be set with a clinician. There is no equivalent risk in healthy kidneys.
Absorption
Over 90% of protein from animal sources; roughly 70–90% from plant sources
Helps absorption
- cooking, which denatures protein and improves digestibility
- combining plant sources across the day to cover all indispensable amino acids
- spreading intake across three or four meals rather than one large one
- resistance exercise, which raises the synthetic response to a given dose
Hinders absorption
- trypsin inhibitors in raw legumes
- tannins and phytates in some whole plant foods
- very large single doses, where the per-meal synthetic response saturates
- advanced age, through anabolic resistance
Top sources
Per 100 g, in g. FoodData Central IDs are resolved by the importer, not written by hand.
- 31 g
Chicken breast, grilled
150 g
- 17.3 g
Tofu, firm
126 g (1/2 cup)
- 10.2 g
Greek yogurt, plain, nonfat
170 g
- 9 g
Lentils, cooked
198 g (1 cup)
- 12.6 g
Egg, whole
50 g (1 large)
- 21.2 g
Almonds
28 g
Ranking these by what you already eat needs the real log — see docs/STATUS.md.
Sources
Last reviewed 2026-08-11