How much protein should a healthy adult under 65 eat?

What the experts say

Siim LandSelf-described anthropologist by education · health author and video essayist

About 0.8 g per pound of body weight per day, roughly 130 to 150 g for an 80 kg person

What it rests onMost evidence that high protein shortens lifespan is in animal models. In humans, low protein intake is associated with higher mortality in the elderly, the RDA is widely considered inadequate, and the muscle-and-strength optimum sits at 0.8 to 1.0 g per pound of lean body mass.

Source: siimland.co ↗

Valter LongoPhD · biogerontologist, Professor of Gerontology, USC

0.31 to 0.36 g per pound of body weight per day under 65, rising slightly after 65

What it rests onProtein intake drives growth hormone and IGF-1 signalling; keeping it low but adequate through midlife lowers the risk of the diseases that signalling promotes.

Source: valterlongo.com ↗

Overview

Both are talking about healthy adults under 65 and both say so. Longo's page raises the number after 65 and names fish, eggs, white meat and goat or sheep products to preserve muscle mass, so the gap narrows with age.

Land's number is pinned to lean body mass in the source he cites and to total body weight in the sentence he writes, which for a lean person is nearly the same and for an overweight person is not. Longo pins his to ideal body weight in the 2024 booklet and to body weight on the web page. Neither website states its own caveat.

Where they agree

More than the numbers suggest. Both reduce animal protein specifically: Land eats about a pound of meat a week and says his approach to meat is precautionary; Longo routes protein to legumes, nuts and fish. Both accept that the elderly need more protein than the young. Both treat muscle preservation as the reason for the floor. The dispute is over the size of the number, not over its direction with age or over the source of the protein.

What would settle it

A randomised trial of protein intake with a hard endpoint, which neither side has and both acknowledge is unlikely. Land says explicitly of the animal-protein question that "it's very difficult to test it in a randomized controlled trial". Short of that, IGF-1 mediation data in humans at both intakes would move it.

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