Even if you’re not exactly sure what protein is technically—or how much protein you need—odds are that you do know how good it makes you feel. Whether you like to start your day with a filling egg scramble, chug the nutrient in shake form after a workout, or cook up a nice steak (or piece of tofu) for dinner, you’re likely familiar with the lasting satisfaction that you get from protein in its many delicious variations. And, as we’ll talk about, protein certainly does enough to earn its reliably good reputation.
While you know protein is a great thing to have, you might also have a few questions. Like, why exactly does your body need it? How much protein do you need to eat, and when should you eat it? And how does your activity level factor into that? Here’s a rundown of what protein does and how much of the nutrient your body needs.
What protein actually is
Protein is one of the three macronutrients (i.e. nutrients the body needs in sizable amounts). Unlike carbs and fat, protein is not usually a major energy source, although we definitely get some of that from it—protein provides four calories per gram. But protein is often referred to as a building block in the body because of its central role in growth and development.
Almost all animal-derived products—meat, poultry, eggs, dairy, fish—contain a significant amount of protein, so they get labeled as protein sources when we’re talking about our diets and nutrition. But protein is also present in a lot of plant-based foods. There’s a good amount in beans, peas, nuts, and seeds, for instance, while vegetables and grains generally contain smaller amounts, according to the U.S. Food and Drug Administration (FDA). Whole grains will have more protein than refined grains, though, which are missing the part of the grain that often supplies a lot of the protein content, as SELF previously reported.
Proteins are made of small units called amino acids. There are 20 different amino acids in total, which can be broken down into two main groups, per the FDA. Nine of the 20 are what are referred to as essential amino acids, meaning that the body is unable to produce them itself and so we must get them from food. The other 11 are nonessential because the body is able to synthesize them out of the essential amino acids or the normal process of breaking down proteins, according to the U.S. National Library of Medicine.
Now when a protein is a good source of all nine of the essential amino acids, we call it a complete protein, according to the FDA. All animal products are complete proteins, and so is soy. When a protein is missing or pretty low in any of those essential amino acids, it’s considered incomplete. Most plant foods are considered incomplete proteins.
The good news for vegetarians, vegans, and lovers of plant foods in general is that you can still easily get all the essential amino acids from eating a wide variety of incomplete proteins. As the FDA explains, incomplete proteins are often just lacking in one or two amino acids, so they can often make up for whatever the other one is lacking. For instance, grains are low in an amino acid called lysine, while beans and nuts are low in methionine. But when you eat, say, beans and rice or wheat toast with nut butter, you’re getting all the amino acids that you do when you eat, say, chicken. While people used to be encouraged to eat foods in combinations at meals, we now know this is not necessary, according to the U.S. National Library of Medicine, as long as you’re eating a variety of complementary incomplete proteins throughout the day.
Why we even need protein
That building block nickname is no exaggeration. The stuff is an integral component of every cell in your body, including, yes, your muscles.
“If we don’t get enough protein, our bodies actually won’t be able to rebuild properly and we’ll start to lose muscle mass,” Colleen Tewksbury, Ph.D., M.P.H., R.D., senior research investigator and bariatric program manager at Penn Medicine and president of the Pennsylvania Academy of Nutrition and Dietetics, tells SELF.
Protein helps repair the microtears that occur in your muscle fibers when they’re strained during exercise, the American College of Exercise (ACE) explains. That process of damage and repair is what maintains and grows your muscle mass.
But protein is not just important for people who work out: In addition to muscle growth and repair, protein is essential to the growth and repair of virtually all cells and body tissues—from your skin, hair, and nails to your bones, organs, and bodily fluids, according to the FDA. That’s why it’s especially important to get enough of it during developmental periods like childhood and adolescence.
Protein also plays a role in crucial bodily functions like blood clotting, immune system response, vision, fluid balance, and the production of various enzymes and hormones, per the FDA. And because it contains calories, it can provide the body energy for storage or use. (But this definitely isn’t its main gig, which we’ll get into in a bit.)
What happens in your body when you eat protein
It’s not like you eat a piece of chicken and that protein goes directly to your biceps. Dietary protein gets broken down and reassembled into the various kinds of proteins that exist in the body. No matter what kind of protein you’re eating—plant or animal, complete or incomplete—your body’s first objective is to break it back down into all the different amino acid units it was assembled from, Dr. Tewksbury explains, through the digestive process.
Then those little singular amino acids get reconfigured (by the liver) into whatever kind of protein your body needs. For instance, some proteins in the body make up antibodies that help the immune system fight bacteria and viruses. Others help with DNA synthesis, chemical reactions, or transporting other molecules, the National Institute of General Medical Sciences explains.
Since your body can’t store excess protein, it will break down any protein it doesn’t need right away and usually stow it away in fat tissue (as triglycerides), according to Merck Manuals. Rarely, if your body is in a fasting state or not getting enough calories coming in from other macronutrients, broken-down protein can be converted into glucose and used for emergency fuel, Whitney Linsenmeyer, Ph.D., R.D., nutrition and dietetics instructor in the Doisy College of Health Sciences at Saint Louis University and spokesperson for the Academy of Nutrition and Dietetics, tells SELF. But this is not typical, because the body prefers carbs as its primary source of energy (followed by dietary fat, if the body is not getting enough carbs). “We can adapt to use protein for energy as well, but it’s not ideal,” Dr. Linsenmeyer says. “Ideally, [our bodies] want to leave it alone to build and maintain body tissues.”
How much protein your body needs
Okay, so how much protein are we talking about here? The amount of protein your body actually requires for the purpose of tissue growth and repair is determined by factors like sex, age, height, weight, health, activity level, and overall calorie need, according to the U.S. National Library of Medicine. So it’s going to vary a lot from person to person.
A good starting point for roughly estimating minimum protein needs is the recommended daily allowance (RDA) for protein, or the average minimum daily intake that’s sufficient to meet the nutrient requirements (i.e. prevent a deficiency) for most healthy individuals (who are sedentary or minimally active). The RDA for protein is 0.8 grams of protein per kilogram of body weight per day, or about 0.36 grams per pound. (So you would multiply your weight in pounds by 0.36 to get your RDA.) For instance, the average 200-pound person needs at least 72 grams of protein per day to meet the RDA.
People with a higher activity level will likely need more. Individuals who work out and want to maintain and/or build muscle mass through diet and exercise definitely benefit from getting more protein than the RDA, Adam M. Gonzalez, Ph.D., C.S.C.S., assistant professor in the Department of Health Professions at Hofstra University, has told SELF.
How much more, exactly, depends on factors like how much you exercise and your body composition goals, as SELF has reported—as well as who you ask. Several large organizations—the Academy of Nutrition and Dietetics (Academy), Dietitians of Canada (DC), and the American College of Sports Medicine (ACSM)—reviewed the research on sports nutrition and agreed that the optimal daily protein intake for active adults and athletes is 1.2 to 2 grams per kilogram of body weight (or 0.5 to 0.9 grams of protein per pound). Similarly, the International Society of Sports Nutrition (ISSN) recommends 1.4 to 2 grams of protein per kilogram of body weight (or 0.6 to 0.9 grams of protein per pound) for most individuals who are working out.
Based on those recommendations, for instance, a 200-pound person would want to get between 100 and 180 grams of protein a day. Generally, the more active you are—the more frequent, strenuous, and long your workouts are—the higher in that range you’ll be, Dr. Gonzalez says.
How you should space out your protein intake
When you eat your protein is just as important as how much you eat. It’s not about simply loading up after exercising or at one meal and skimping on it for the rest of the day. Like we mentioned, the body doesn’t have a protein holding tank like it does for carbs, where it can siphon away extras for quick access when we need it.
That’s why the best way to get your protein is split up throughout the day. Eating a good amount of protein at different points in the day helps your body direct protein where it’s needed, when it’s needed—not to mention, keeps you feeling satisfied and energized. So take a look at your daily amount (the recommendations above), and see how you can break that up in your various meals throughout the day.
Spacing out protein intake is also super important for active individuals. That’s because muscle repair and growth are “greater when you consume adequate protein at breakfast, lunch, and dinner,” Dr. Linsenmeyer explains. Yes, “protein is vital after a workout,” Yasi Ansari, M.S., R.D., C.S.S.D., national media spokesperson for the Academy of Nutrition and Dietetics and assistant director of Performance Nutrition for UC Berkeley Athletics, has previously told SELF. “But it is important for people to know that more [all at once] is not necessarily better.”
Your muscles are going to be hungrier for protein for at least 24 hours after exercising, Dr. Gonzalez says—so basically, most of the time, if you work out most days. The Academy/DC/ACSM recommend getting 15 to 25 grams of protein (or 0.25 to 0.3 grams per kilogram of body weight) about every three to five hours to maximize muscle repair. The ISSN suggests getting 20 to 40 grams (or 0.25 grams per kilogram of body weight) every three hours or so. So a good target combining those ranges is 20 to 30 grams of protein at a time, as SELF has explained. If you want to get a bit more precise, convert your body weight in pounds to kilograms (divide your weight in pounds by 2.2), and multiply that number by 0.25 or 0.3. So for a 200-pound person, for instance, that works out to 23 to 27 grams of protein.
You want a similar amount after working out, too, when your muscles need immediate repair. How much protein your muscles can take in after exercising depends on things like the type and intensity of your workout and your body composition, Ansari explains—so lifting weights for an hour, for example, will make your muscles thirstier for protein than a 30-minute cardio workout. In general, though, the Academy/DC/ACSM recommend getting that same protein hit (15 to 25 grams of protein, or 0.25 to 0.3 grams per kilogram of body weight) within two hours of exercising in order to maximize muscle repair, while the ISSN again recommends aiming for 20 to 40 grams (or 0.25 grams per kilogram of body weight).
The bottom line on protein? This nutrient is vital to our bodies, so you want to get at least the recommended minimum no matter what. If you work out, get a good bit more than that. And instead of loading up at one meal, spread the protein love throughout your day.