How much protein do you actually need, and does it matter whether it comes from plants or animals?

Joel H. FuhrmanMD · board-certified family physician, nutrient-density author

About 0.9 g per kg of body weight for a healthy young adult, more for older adults and athletes, and from plants. Counting is unnecessary because a varied plant diet at adequate calories lands there anyway.

What it rests onHe argues the 0.8 g/kg RDA rests on early nitrogen-balance work and that indicator-amino-acid methods put the minimum nearer 0.9 g/kg, publishing a life-stage table (older adults 1.0 to 1.5, athletes 1.2 to 2.1) and putting a typical 1700 to 1800 calorie day of his diet at roughly 60 to 70 g of protein. His objection to going higher is not the protein but the animal foods that usually carry it: IGF-1, arachidonic acid, saturated fat, carnitine and heme iron. He sells a plant protein powder and does not say so in the article.

Peter AttiaMD · longevity physician, founder of Early Medical

1.6 to 2.2 g per kg per day, and plant protein makes the requirement higher rather than lower.

What it rests onHe argues the RDA was derived from nitrogen-balance studies in young, lean, often inactive men and does not account for population variability, older adults' anabolic resistance, pregnancy, childhood, injury recovery or resistance training. On the plant question specifically he writes that plant proteins are absorbed more poorly and stimulate anabolic processes less well, making the RDA insufficient for people relying on them. His own disclosures list an investment in and advisory role at a protein food company, unmentioned in the article.