Food

Protein by age: how much you need at each stage

For most adults the answer is 0.83 g of protein per kilogram of body weight a day, the safe level set by the joint FAO, WHO and UNU expert consultation in 2007: 50 g a day at 60 kg, 66 g at 80 kg. Children need more per kilo (1.31 g/kg at 6 months, 0.90 at 3 years) but less in total, pregnancy adds 1, 10 and 31 g a day by trimester, and from 65 the European PROT-AGE and ESPEN expert groups advise at least 1.0 to 1.2 g/kg for healthy older people, 1.2 to 1.5 g/kg for those who are ill or malnourished. In healthy older men, muscle needed about 0.40 g/kg in one meal to respond fully, against 0.24 g/kg in young men.

Where the 0.83 figure comes from

The adult number rests on nitrogen balance: measure the nitrogen people lose at known protein intakes, and find the intake at which loss and intake match. The 2007 report of the joint FAO, WHO and UNU expert consultation used a meta-analysis of 19 such studies with 235 healthy adults, each tested at 3 or more intakes, and put the median requirement at 0.66 g of protein per kg of body weight a day. Because requirements vary between people, the report set the safe level at the 97.5th percentile, 0.83 g/kg a day, enough for all but 2.5 percent of healthy adults, men and women, at every age from 18 upwards.

The US Recommended Dietary Allowance of 0.8 g/kg and the European Food Safety Authority's reference intake of 0.83 g/kg from 2012 come from the same balance data, so the three reference bodies differ by a rounding. Two limits are worth knowing: nitrogen balance says how much protein keeps an adult in equilibrium, not how much is best for muscle or bone, and 0.83 g/kg is a population floor, not an individual ceiling. The report sets no upper limit, calls twice the safe level unlikely to carry risk, and advises caution at 3 to 4 times it.

Children need more per kilo, less in total

Growth changes the arithmetic: a child builds new tissue as well as maintaining it, so the safe level per kilogram is highest in infancy and falls through childhood: 1.31 g/kg a day at 6 months, 1.14 at 1 year, 0.90 at 3 years, 0.87 at 4 to 6 years and 0.92 at 7 to 10 years. Between 11 and 18 the figures run from 0.90 g/kg down to 0.84, already close to the adult 0.83.

The totals are still modest. At the WHO reference weights that is about 9 to 10 g a day at 6 months, 13 g at 3 years and 47 g (girls) to 58 g (boys) at 15 to 18. Weight varies almost 2-fold within each age band, so multiply by the child's actual weight. Pregnancy and breastfeeding add to the adult 0.83 g/kg: 1 g a day in the first trimester, 10 g in the second and 31 g in the third, then 19 g a day for the first 6 months of breastfeeding and 13 g after, from ordinary food rather than supplements.

From 65, the advice moves up

The WHO consultation gave older adults the same 0.83 g/kg as everyone else: the 4 balance studies behind the 1985 floor of 0.75 g/kg were inconsistent, 2 later comparisons of young and old found no difference, and a study had reversed sarcopenia, the age-related loss of muscle, with resistance exercise on 0.8 g/kg a day. In 2013 the PROT-AGE study group, appointed by the European Union Geriatric Medicine Society, reached a different conclusion: adults over 65 should average at least 1.0 to 1.2 g/kg a day, those who exercise and are active at least 1.2 g/kg, and most older adults with an acute or chronic illness 1.2 to 1.5 g/kg. The one exception it names is severe kidney disease, an estimated filtration rate below 30 ml/min per 1.73 m² without dialysis, where protein may need to be limited. The 2014 ESPEN expert group set the same 1.0 to 1.2 g/kg for healthy older people, and 1.2 to 1.5 g/kg for those malnourished or at risk of it through acute or chronic illness.

One reason is a change in how muscle responds to food. A 2015 analysis in the Journals of Gerontology pooled dose-response data from six of the authors' own studies, 43 healthy men of about 71 years and 65 of about 22, who had eaten single portions of 0 to 40 g of protein while muscle protein synthesis was measured. The older men needed 0.40 g/kg of body weight in one sitting before synthesis reached its plateau, against 0.24 g/kg in the young men; per kilogram of lean mass the figures were 0.60 and 0.25. For a 70 kg man that is roughly 28 g in a meal at 71 against 17 g at 22. The analysis is retrospective, all male and measures synthesis over hours rather than muscle over years; the gap per kilogram of body weight also fell just short of statistical significance (p = 0.055), while the gap per kilogram of lean mass was clear. Treat its numbers as a guide to meal size, not a prescription.

Midlife and the study that split the advice by age

In 2014 Levine, Longo and colleagues published in Cell Metabolism an analysis of 6,381 US adults aged 50 and over from the NHANES III survey, followed for up to 18 years. Protein was classed as high at 20 percent or more of calories, moderate at 10 to 19 percent and low below 10 percent. Among those aged 50 to 65, the high-protein group had a 74 percent higher rate of death from any cause (hazard ratio 1.74) and more than four times the rate of cancer death (4.33) of the low-protein group; when the protein came from plants, the associations weakened or disappeared. Over 65 the sign flipped: high protein went with a 28 percent lower rate of death from any cause (0.72) and a 60 percent lower rate of cancer death (0.40).

The limits are large, and the authors list them. Intake came from a single 24-hour recall, then linked to deaths over 18 years. The analysis is observational: it shows that middle-aged Americans who ate a lot of animal protein around 1990 died sooner, not that the protein caused it, and the confidence intervals are wide (1.02 to 2.97 for the all-cause result). In their own words the pattern they suggest is low protein in middle age, the 0.7 to 0.8 g/kg of the US reference value rather than the 1.0 to 1.3 g/kg they say adults of 19 to 70 commonly eat, followed by a moderate intake in old age. An 80 kg adult at 0.83 g/kg on 2,000 calories eats 66 g, about 13 percent of calories and at the lower end of the study's moderate band; at 1.2 g/kg after 65 it is 96 g, about 19 percent.

What the grams look like, and who should check first

MedlinePlus, the US National Library of Medicine's health service, gives a simple unit: 30 g (1 ounce) of meat, fish or poultry, 1 large egg, 65 g of cooked beans or lentils or 60 ml of tofu each supply about 7 g of protein, and every gram of protein carries 4 calories. A 66 g day for an 80 kg adult is therefore 9 or 10 of these units, and a 25 to 30 g meal is 4 of them. The same page frames protein as 10 to 35 percent of calories. The Protein and Fibre Target works the per-kilogram figures out for your weight and age, and the guide on strength training after 40 covers the exercise half of the PROT-AGE advice.

Some people should set the number with a professional, not take one from a table. With chronic kidney disease and no dialysis, above all at an estimated filtration rate below 30, more protein can be the wrong direction; on dialysis the target is set by your kidney team and is often higher rather than lower. With diabetes, protein-rich meals change how blood glucose and any insulin dose behave, so tell your care team. In pregnancy, use the additions above and stay with ordinary food rather than high-protein products. Under 18, use the per-kilogram values for children without powders on top. With a history of an eating disorder, protein targets can become another number to over-control, and support comes before arithmetic. Unexplained weight or muscle loss after 65 is a reason to see a doctor, not simply a cue to eat more protein.

Working out your own number

Frequently asked

How many grams of protein do I need a day?

For a healthy adult, 0.83 g per kg of body weight a day, the WHO safe level from 2007: 50 g at 60 kg, 58 g at 70 kg and 66 g at 80 kg. From 65 the PROT-AGE group advises 1.0 to 1.2 g/kg, which is 70 to 84 g at 70 kg.

Do older adults really need more protein than younger ones?

The WHO consultation of 2007 found no basis for a separate figure, but the PROT-AGE group in 2013 recommended 1.0 to 1.2 g/kg for people over 65 because older muscle responds less to a given dose. A 2015 analysis found older men needed about 0.40 g/kg of protein in a meal to stimulate muscle building fully, against 0.24 g/kg in men of about 22.

Is a high-protein diet risky in middle age?

One observational study of 6,381 US adults found that at 50 to 65 those getting 20 percent or more of calories from protein had a 74 percent higher death rate over 18 years, while over 65 the high-protein group had a 28 percent lower rate. It relied on a single 24-hour recall and cannot show cause. An adult eating the 0.83 g/kg safe level gets roughly 10 to 13 percent of calories from protein, inside the study's moderate band.

How much protein should one meal contain?

In the 2015 dose-response analysis, muscle protein synthesis plateaued at 0.24 g/kg per meal in young men and 0.40 g/kg in men of about 71: roughly 17 g and 28 g for a 70 kg person. After 65, three meals of 25 to 30 g each cover the 1.0 to 1.2 g/kg target without a very large dinner.

How much extra protein in pregnancy and while breastfeeding?

The WHO consultation adds 1 g a day in the first trimester, 10 g in the second and 31 g in the third to the adult 0.83 g/kg, then 19 g a day for the first 6 months of breastfeeding and 13 g after that. It asks for the extra to come from ordinary food, not high-protein supplements.

Do children need protein supplements to grow?

No. The safe level is 1.31 g/kg at 6 months and falls to 0.84 to 0.87 g/kg by 15 to 18, which at reference weights is about 13 g a day at 3 years and 26 g at 7 to 10. Ordinary meals with eggs, dairy, pulses, fish or meat reach these amounts; a child who is not growing as expected should see a doctor rather than be given powders.

Sources

• WHO, FAO and UNU 2007: Protein and amino acid requirements in human nutrition, report of a joint expert consultation (WHO Technical Report Series 935) · Median requirement 0.66 g/kg a day and safe level 0.83 g/kg (97.5th percentile) from a meta-analysis of 19 nitrogen balance studies with 235 adults; tables 46 to 48 give grams by body weight for adults, safe levels by age for children, and the additions for pregnancy and lactation; Table 48 gives 1, 10 and 31 g for pregnancy (the chapter text rounds the second trimester to 9 g); full PDF read
• Bauer et al. 2013, Journal of the American Medical Directors Association: Evidence-based recommendations for optimal dietary protein intake in older people, PROT-AGE study group · Study group appointed by the European Union Geriatric Medicine Society; 1.0 to 1.2 g/kg a day over 65, at least 1.2 g/kg when active, 1.2 to 1.5 g/kg with acute or chronic illness, exception for severe kidney disease below eGFR 30 in people not on dialysis; abstract read; the 2014 ESPEN expert group (Deutz et al., Clinical Nutrition) gives at least 1.0 to 1.2 g/kg for healthy older people and 1.2 to 1.5 g/kg for those malnourished or at risk of malnutrition through acute or chronic illness, so the higher band covers a narrower group than the PROT-AGE wording
• Moore et al. 2015, Journals of Gerontology Series A: Protein ingestion to stimulate myofibrillar protein synthesis requires greater relative protein intakes in healthy older versus younger men · Retrospective analysis of 6 earlier studies from the authors' own laboratories, 43 men of about 71 and 65 of about 22 years, all healthy and all male, single doses of 0 to 40 g; synthesis plateaued at 0.40 g/kg body mass in the older men against 0.24 g/kg in the younger, 0.60 against 0.25 g/kg lean mass (body-mass difference p = 0.055, lean-mass difference p below 0.01); linked here on the University of Illinois page of co-author Burd, which carries the published abstract, because the journal and doi.org answer 403 to automated requests (doi 10.1093/gerona/glu103); author manuscript also read in full
• Levine et al. 2014, Cell Metabolism: Low protein intake is associated with a major reduction in IGF-1, cancer and overall mortality in the 65 and younger but not older population · Observational cohort, not a trial: 6,381 US adults aged 50 and over from NHANES III, 18 years of follow-up, single 24-hour recall; hazard ratios 1.74 (all-cause, 95% CI 1.02 to 2.97) and 4.33 (cancer, 1.96 to 9.56) for high versus low protein at 50 to 65, 0.72 and 0.40 at 66 and over; the authors conclude for low protein intake in middle age (the 0.7 to 0.8 g/kg reference value) and moderate intake in old age; open-access full text read
• MedlinePlus, US National Library of Medicine: Protein in diet · Protein as 10 to 35 percent of calories, 4 calories per gram; about 7 g of protein in 30 g of meat, fish or poultry, 1 large egg, 65 g of cooked beans or lentils or 60 ml of tofu

Read on

Tools that fit

This guide is for general information. It does not replace medical advice or an examination.