Americans are obsessed with protein. Protein powders make up 70 percent of the country’s $6.7 billion sports nutrition market, according to market research firm Euromonitor International, and the high-protein diet has officially become the nation’s favorite. But while athletes need more protein than the general population, experts say, there is a point of diminishing returns.
“Athletes are better off consuming 1.6 grams of protein per kilogram of bodyweight per day [over the government’s recommendation of 0.8 grams],” says Stuart Phillips, director of McMaster University’s Centre for Nutrition, Exercise, and Health Research in Ontario, Canada. For a 150-pound athlete, 1.6 grams per kilo works out to about 109 grams of protein daily, or 2.5 chicken breasts. “That’s not to say you can’t consume more,” Phillips says, counter to theories that eating too much protein can cause kidney failure or bone loss. “But after about 1.8 grams per kilogram per day, the benefits start to level off.”
Those benefits include muscle maintenance and repair, as well as support of the health of ligaments, tendons, and bones—parts that are primarily made of a protein called collagen that can also break down during exercise.
“Think of your muscles like a brick wall; you put new bricks in to keep it fresh and pull bricks out at the same time,” Phillips says. The bricks are amino acids, the compounds your body breaks food protein into. Phillips says two proteins found in milk make the best new bricks: whey, “a rapidly digested protein that turns on the rebuild phase” and casein, a more slowly digested protein.
Recent studies have found that consuming protein during exercise doesn’t have much effect on performance or recovery, though Phillips points out it may be beneficial during ultra-endurance events like Ironman or an ultramarathon.
Protein eaten before a workout can kill hunger and may help attenuate muscle breakdown, but research on pre-exercise protein benefits is far from conclusive. After exercise, however, “your muscles are like sponges. They’re ready to soak up nutrition and they’re ready to rebuild,” Phillips says, though researchers are still debating if there’s an optimal time post-workout to fuel up.
The kicker: Power athletes like weight lifters don’t need more protein than any other athlete. “If you get 1.6 to 1.8 grams per kilo per day, it doesn’t matter if you’re lifting six days a week or two, or if you’re running two or six or seven,” Phillips says. After that amount, the benefits don’t increase.