What Is Protein?

By: ray.perry : October 17, 2013

After water, protein is the most plentiful substance in your body. Every part that makes you, well, you – your eyes, your skin, your muscles, your blood, even your bones – is made up of cells that contain protein.

Proteins are large molecules composed of amino acids. Different combinations of amino acids – there are 20 critical to human health – make up different proteins, all of which play specific roles in the body.

"Protein is just a mixture of amino acids that are bound together," says Becci Twombley, director of sports nutrition at the University of Southern California. "Think of amino acids as letters, and those letters make up different words. Well, the human body needs all those words to grow."

That's the key: "to grow." The average adult's body is made up of 60 to 90 trillion cells, hundreds of millions of which die every minute. Fortunately, more new cells are created every minute, and proteins are the machinery that maintain, repair and build them.

Without protein, there is no life. But the body can't store protein the way it stores the other two macronutrients – fat and carbohydrates – so the only way to get the protein your body needs is through food.

The best sources? Lean beef and other red meat, poultry, eggs, fish, soy, nuts, seeds, legumes and milk. Twombley, who helps plan the nutrition and recovery of 700 USC athletes, says an average adult needs at least 0.8 grams of protein per kilogram of bodyweight, even more for young children, pregnant and nursing women, and athletes. (To convert your bodyweight from pounds to kilograms, divide by 2.2.)

"A really good estimate is somewhere between 1 and 1.2 grams per kilogram," Twombley says. "Most of the athletes we work with are at 1.8 grams per kilogram."

The best approach, she says, is to mix animal and plant proteins. With 6 grams of pistachios per 28g serving (approximately 49 nuts), pistachios are a good source of plant protein.

"We know that combining animal proteins with plant proteins will maximize recovery," she says. "Let's say you have Greek yogurt, soy milk and pistachios. Now you have three beneficial proteins working in concert, making your recovery and growth even faster."

STAY TUNED: Our next article will help demystify protein for athletes.