How many grams of protein per day?

Protein needs depend on body size, life stage, health status, and activity. For generally healthy adults the United States National Academies of Sciences, Engineering, and Medicine recommends 0.8 grams of protein per kilogram of body weight per day. That reference intake is intended to meet the needs of most sedentary adults and is the common baseline used by health professionals when planning diets.

General adult needs
Translating that guideline into everyday terms means a 70 kilogram adult needs about 56 grams of protein each day. The recommendation represents the minimum to avoid deficiency and maintain basic nitrogen balance rather than an optimal target for maintaining or building muscle. Worldwide agencies such as the World Health Organization provide similar guidance, emphasizing that requirements must be adjusted for growth, pregnancy, and illness.

Higher needs for athletes and older adults
People who exercise regularly, particularly those doing resistance training, and older adults trying to preserve muscle mass have higher requirements. Research led by Stuart M. Phillips at McMaster University and colleagues shows that intakes above the standard 0.8 grams per kilogram can support muscle maintenance and gains. A meta-analysis of resistance training studies reported an average optimal intake around 1.6 grams per kilogram per day for maximizing muscle hypertrophy, while professional sports nutrition groups commonly recommend ranges roughly between 1.2 and 2.0 grams per kilogram depending on training intensity and goals.

Causes and consequences of different intake levels
Physiological reasons for higher needs include increased muscle protein turnover with exercise, reduced anabolic sensitivity with aging, and increased demands during pregnancy and illness. Insufficient protein over time contributes to loss of lean body mass, weaker immune responses, slower recovery from injury, and impaired growth in children. Extremely high intakes do not improve muscle beyond a point and can pose risks for people with preexisting kidney disease. There are also environmental and cultural consequences: diets high in animal protein have greater greenhouse gas emissions and land use than plant-forward diets, and in many low-income regions cultural reliance on staple grains can produce marginal protein status despite adequate calories.

Practical application
Start from the baseline of 0.8 grams per kilogram for healthy, sedentary adults and scale up according to activity, age, and life stage. For strength training or competitive athletes, evidence summarized by Stuart M. Phillips at McMaster University supports aiming near 1.6 grams per kilogram, with individualized adjustments between about 1.2 and 2.0 grams per kilogram based on goals and total energy intake. For older adults, modest increases to around 1.0 to 1.2 grams per kilogram can help protect muscle and independence. Food sources, meal timing, and combining plant and animal proteins influence adequacy, so working with a registered dietitian or qualified clinician is advisable for tailored recommendations.