Protein 101: Why it matters and how much you really need

What is the updated daily protein recommendation for adults?

How are fast-food chains adapting to high-protein trends?

Is peanut butter a complete protein source?

Why are antidepressants overprescribed for menopause symptoms?

Whether it’s at the gym, in a doctor's or dietitian's office or simply while shopping at the grocery store, it’s hard to miss the constant reminders to eat more protein. After all, protein-boosted smoothie recipes, meal kits, fitness ads and even snack packaging are everywhere, each seeming to promise better energy, stronger muscles or easier weight control than the last. And today, there's more emphasis on protein intake than ever, fueled in part by recent updates to U.S. Dietary Guidelines.

This level of attention makes sense, as protein is far more than a trendy nutrient or fitness buzzword. It's a fundamental part of what makes our bodies work and is “in nearly every structure and function in the body,” says Amy Goodson, a nutritionist and registered dietitian at The Sports Nutrition Playbook. Indeed, from the way our cells communicate, to how our immune systems protect us, to how our muscles move and repair themselves, protein is constantly at work behind the scenes.

Yet despite such importance and emphasis, many people still don’t fully understand how protein works, why it matters or the best ways to get enough of it in their diet. Here’s what to know.

What is protein?

Protein is one of the body’s three macronutrients, along with carbohydrates and fat. Each provides calories and energy, but they serve different purposes. Protein's main role is to supply the building materials your body needs to grow, repair and function.

Need a news break? Check out the all new PLAY hub with puzzles, games and more!

Chemically, it's made of smaller units called amino acids, explains Kristina Cooke, a licensed nutritionist and registered dietitian with the Academy of Nutrition and Dietetics. “The body takes these and distributes them where needed.”

There are 20 amino acids that humans use – some of which the body can make on its own, while others must come from food. That is why, as Goodson notes, “eating protein-based foods are essential.” 

Animal-based foods are known as complete sources of protein because many of them contain all essential amino acids. Some of the best animal sources include chicken breast (about 22.5 grams of protein in a 3.5-ounce serving), eggs (about 6 grams in a large egg), Greek yogurt (about 16 grams per 2/3 cup serving) and salmon (about 22 grams in a 3-ounce portion). Other good animal-based sources include lean beef, turkey, tuna, cottage cheese and milk.

But plant-based foods can be excellent protein sources as well. One cup of cooked lentils contains about 18 grams of protein, while about three servings of almonds contains some 21 grams of the macronutrient. Foods like quinoa, tofu, chickpeas, black beans, edamame and chia seeds are other strong plant-based options.

Yes, quinoa is popular and delicious. But is it actually good for you?

What does protein do for your body?

No matter where you get it, protein is involved in nearly every biological process. Cooke explains that proteins “act as enzymes to help catalyze chemical reactions in the body, helping create the structure of cells and acting as transporters.” One example is hemoglobin, which she notes is “a protein bound to red blood cells that helps transport oxygen.” Without it, oxygen could not reach your tissues.

Another major role of protein is in growth and repair. This matters because the body is constantly breaking down and rebuilding tissues, and protein provides the amino acids that make this renewal possible. This is why protein is so often associated with muscle growth and maintenance.

Protein is also essential for immune function as "protein helps form antibodies and immune cells that protect the body from infection,” says Goodson. This is why, when you are sick or injured, your protein needs increase as your body is working harder to heal and defend itself.

Another critical role of protein is in the production of enzymes that help break down food, release energy and build new molecules, as well as in the production of hormones such as insulin, which regulates blood sugar.

Protein also supports structural integrity. “Structural proteins like collagen and keratin support healthy tissues,” Goodson says, which is why protein matters for skin, hair and nails.

And because protein takes longer to digest than carbohydrates, Goodson notes that it “helps improve satiety” and “is essential for helping to maintain steady blood sugar at meals.” This is one reason higher-protein meals tend to keep people full longer and help prevent energy crashes.

Important: How to test your blood sugar levels and why it's critical for some people

How much protein do I need every day? 

To receive these benefits, you need enough protein in your diet. The Recommended Dietary Allowance (RDA) for adults has recently been updated from 0.8 grams of protein per kilogram of body weight daily to 1.2 to 1.6 grams per kilogram of body weight – a 50% to 100% increase from the older minimum. This means that someone who weighs 150 pounds (about 68 kilograms), will want roughly to consume roughly 82 to 109 grams of protein per day.

At the same time, individual medical providers and other health experts might offer different takes, including some who prefer the previous guidance. And Goodson notes that individual needs vary greatly and some people may benefit from eating more protein than current recommendations - especially those who are physically active or doing strength or endurance training, because protein helps “support performance and recovery.”

Still, more isn't always better. While “most healthy adults can handle high quantities of protein,” Cooke says, “individuals with certain health conditions, like chronic kidney disease, can further damage kidneys with high intakes of protein.” This is why, she explains, “it’s extremely important to discuss personal protein needs with your registered dietitian.”