Bodybuilders can eat up to 20 pounds of protein every day – and yet only the first few ounces, or 30 grams, actually goes towards muscle building.

Researchers from the University of Texas Medical Branch made the discovery when they tested protein-rich diets on a group of young and elderly volunteers. They were tested after eating four ounces of lean beef, and then 12 ounces of beef. There were no improvements in muscle quality after eating the four-ounce portion. “This suggests that at around 30 grams of protein per meal, maybe a little less, muscle protein synthesis hits an upper ceiling,” said Douglas Paddon-Jones, the lead researcher.

(Source: Journal of the American Dietetic Association, 2009; 109: 1582).