The standard protein recommendation for adults (0.8g/kg/day) isn't enough to keep protein levels stable in men who've been vegan for a year and aren't very active.

When 17 men who've been vegan for at least a year ate a diet with 0.8 grams of protein per kilogram of body weight for 5 days, their bodies lost protein, as shown by negative nitrogen balance numbers.

Vegan men who don't exercise much and have been vegan for a year lose protein when eating the standard protein recommendation for 5 days.

For these vegan men, how long they'd been vegan, their age, muscle mass, or activity level didn't affect whether their bodies were losing protein on this diet.

Based on the protein loss observed, vegans might need about 20% more protein (0.96g/kg/day) to stay balanced.