The athlete's guide to protein

The best sources, how to time to time it right, and why you're probably not getting enough

Traditionally,athletes looking to build muscle have stayed laser-focused on protein. Meanwhile, runners and cyclists focus more on carbs or fat to keep them powered through their respective workouts, often fearing protein will make them bulky and slow. But new research is showing that not only can every athlete improve their performance by consuming protein, but also by consuming way more of it than is commonly recommended.

Here's why: Amino acids in protein help repair your muscle fibers so they grow back bigger and stronger. It’s these same amino acids that allow protein to help your cardio fitness. Having a constant stream of essential and branched chain amino acids to your working muscles during high-intensity aerobic exercises helps to serve as an additional fuel source, explains Paul Arciero, director of the Human Nutrition & Metabolism Laboratory at Skidmore College in New York. Plus, protein does more than just repair your damage. “Protein is a building block for the whole body, not just muscles,” adds New York-based dietician Jennifer Senecal. “We draw from dietary protein to keep the immune system healthy, to produce new cells to replace worn out ones, and to make repairs to other tissues in the body.”

How much protein you really need

The Academy of Nutrition and Dietetics recommends that athletes aim for roughly one gram of protein per kilogram of body weight per day to maintain muscle mass and 1.4 to 1.8 g/kg/d to build muscle. But the latest science suggests that every exerciser could benefit from hitting the upper end—or more—of that amount, not just those looking to add bulk.

In two separate studies led by Arciero, active men and women were put on a diet of two g/kg of protein a day. They spent 12 weeks doing a combination of resistance training, interval training, stretching, and endurance. The results: compared to controls who ate only one g/kg/d of protein, both sexes increased their muscular power and strength, with the men also increasing their aerobic performance and flexibility and the women their cardiovascular health and muscular endurance. (The reason there was a difference between genders could be that men and women start from different baselines: Women are naturally more flexible and often do more cardio, so men have more room to improve in flexibility and aerobic endurance. Meanwhile, women have less lean muscle mass so when they start building more thanks to strength training and more protein, they show greater improvements in muscle endurance, Arciero explains.) Pushing it even further, a separate study inthe American Journal of Clinical Nutrition found that men who were burning a ton of calories through three days of HIIT, two days of strength training circuits, and one day of plyometrics, gained more lean body mass and lost more fat eating 2.4 g/kg of protein a day.

But, there is a ceiling. Research in theJournal of the International Society of Sports Nutrition found that when active men and women kicked their daily protein intake up to 4.4 g/kg/d, they didn't see any positive or negative effects on their weight, lean body mass, or body fat percentage.

In the end, how much protein you should consume is super individual but the existing research points to starting with at least two g/kg of protein a day.

How to time your protein consumption for optimal performance

Just as there's a limit to total protein consumption in a day, there’s a max to how much protein your muscles can absorb at one sitting. Senecal says it’s typically thought to cap at 20 grams (equivalent to about three ounces of chicken) though other experts say up to 40 grams.

Protein pacing is something Arciero has studied in depth. His take: “Ideal timing is consuming protein about every three hours throughout the day, beginning within 60 minutes of waking and ending within two hours of going to bed,” Arciero says. He advises aiming for 20 to 40 grams of protein per meal with four to six meals per day (that’s .25 g/kg per meal, and .5 g/kg at your dinner, he adds). Arciero says this way of eating will benefit athletes in all types of sports (and both genders) and also maximize body composition, enhance physical performance (like muscular power), increase strength and endurance, and increase aerobic power and flexibility.

As for the idea that you need to pack your protein in right after you finish exercising, there is a window in the two hours after you work out in which your muscles are able to synthesize protein more efficiently, Arciero says. But it’s not as crucial as it may seem. The window stays open (though less so) for roughly 24 hours, says that meta-analysis inNutrition & Metabolism.

Timing your pre- and post-exercise meals to be within three to four hours of one another is more important to muscle growth and recovery than any post-workout window alone, according to a2013 meta-analysis in theJournal of the International Society of Sports Nutrition. Having a stock of amino acids already in your system allows your body to capitalize on every second of that "window" of muscle protein synthesis as soon as it opens—that is, the second you start doing damage to your muscles. Senecal recommends snacking on a mix of carbs and protein two to three hours before your workout to “preload” protein for recovery and top off glycogen stores in the muscles for energy.

What kind of protein is best

Aim to get the majority of your protein from real food. “For omnivores, animal protein is the most bioavailable source,” Senecal says. The protein in animal products is considered "complete," containing all needed amino acids and thus is easier for the body to use, she explains. Opt for foods such as poultry, fish, yogurt, and eggs. For vegetarians and vegans, she recommends nuts and nut butters, tofu/soy protein, legumes like beans and lentils, seeds (like chia, pumpkin, flax) and whole grains (like wheat, quinoa, and brown rice). For reference, just one egg has about seven grams of protein and one cup of lentils has 18 grams, according to the USDA.

Both experts agree that when it comes to protein powders (to be used only to supplement what you're not able to get from real food), whey still reigns king. “It’s well established that whey protein is superior to all other proteins for improving body composition and muscle performance because it contains the most leucine, which is the strongest stimulus to increase protein synthesis,” Arciero says. The best plant-based option is soy or a brown rice/pea blend, both of which have the closest complete amino acid profile.