Protein is the stuff of life. From your hair to your fingernails to your muscles, protein is the glue that holds each cell in your body together, and what makes up many major hormones and antibodies. That's why getting enough protein in your daily diet is important. New evidence suggests exactly how much you need depends on a host of factors: your diet, age, health, activity level and—for women—whether you're eating for two. Here's everything you need to know to make sure you're eating the right amount of protein.
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Current guidelines, established by the Institute of Medicine in 2002, recommend adults 19 years of age and older consume 10 to 35 percent of their daily calories from protein. That's about 200 to 700 calories from protein for a 2,000-calorie diet. Another way to calculate how much protein you need each day is to multiply 0.8 grams of protein per kilogram of your body weight. With a little math, this translates to 54 grams of protein for a 150-pound woman, or 65 grams for a 180-pound man.
Here are some examples of what 10 grams of protein looks like:
• 2 small eggs
• 2 1/2 tablespoons peanut butter
• 1 cup cooked quinoa
• 3/4 cup cooked black beans
• 1 cup uncooked oats
• 1/2 cup Greek yogurt
Meat is an obvious protein source, and here's a handy trick for calculating grams of protein in most meats: 1 ounce of meat has 7 grams of protein, with a 3- to 4-ounce portion (a piece of meat about the size of an iPhone 6) providing around 30 grams of protein.
But the IOM's recommendations set the minimum amount of protein you need to eat in order to avoid falling short of this vital nutrient. (Not getting enough protein could lead to progressive muscle loss and other health issues.) Recent research suggests that aiming for more, between 1.3 and 1.8 grams/kilogram of body weight (approximately 88 to 122 grams for women, 105 to 145 grams for men), may be optimal for health, especially when it comes to warding off age-related muscle loss.
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So does this mean you can eat the 12-ounce steak for dinner? Not exactly.
Protein deficiency in the U.S. is a rarity and, if you're eating a varied diet, there's no need to go out of your way to "beef" up your intake. But how you spread your protein out throughout the day may matter just as much—if not more—than how much you eat.
Americans' protein consumption is skewed: We typically skimp on protein in the morning and load up in the evening. But research suggests that evenly splitting up your protein consumption is the best way to support your muscles.
People who ate about 30 grams of protein at each meal—breakfast, lunch and dinner—had 25 percent greater muscle growth, compared with those who ate the same total amount primarily at dinner, according to a study published in the Journal of Nutrition.
"Since we don't have a storage form of protein in our bodies besides our muscles, if we're not eating protein at each meal, then we may be losing that muscle mass," says Jessica Crandall, R.D.N, a certified personal trainer and spokesperson for the Academy of Nutrition and Dietetics. And less muscle mass could mean a decrease in metabolism (which makes it harder to lose weight).
For breakfast, try two eggs with a cup of yogurt and fruit, or 3/4 cup oatmeal, 1/2 cup Greek yogurt and a handful of pumpkin seeds. At lunch, toss half a chicken breast or half a can of beans into your salad for a protein boost.
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Eating too much protein can mean missing out on nutrients from carbohydrates (like fiber) and healthy fats. That's why experts say to stick to eating about one-third of your daily calories from protein, and keeping to a rough daily maximum of 2 grams/kilogram body weight. That's about 140 to 160 grams per day. Overconsuming certain sources of protein—we're looking at you, red meat—has been linked to an increased risk of cardiovascular disease and certain cancers, so vary your protein sources for the most benefit.
Also, don't worry about your protein intake putting you at risk of kidney stones or osteoporosis. (The concern: digestion of protein releases acids that need to be neutralized by calcium—which may be pulled from bones.) In fact, recent research has found that eating in the higher recommended range may be beneficial for bone health, especially when you're eating enough calcium. And unless you have kidney disease, your protein intake is unlikely to cause harm.
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Good news for those forgoing animal products: If you're eating enough calories, opting for a plant-based diet doesn't automatically mean you're not consuming enough protein. According to the Academy of Nutrition and Dietetics, the terms "complete" and "incomplete" protein are misleading. "Protein from a variety of plant foods, eaten during the course of a day, supplies enough of all indispensable (essential) amino acids when caloric requirements are met," the Academy said in a 2016 position statement.
Vegetarians and vegans may need to pay a bit more attention to what foods give them the best protein-for-calorie value than the average meat-eater, but eating a varied diet that includes protein-rich legumes and soy will keep your body and muscles humming along just fine. Other great vegetarian sources of protein: eggs, Greek yogurt, nuts, quinoa and peanut butter. See our Top Vegetarian Protein Sources if you need help eating more protein.
Protein isn't just a concern for the shake-guzzling bodybuilder wanting to build muscle—or the elite distance runner trying to keep it. Adequate protein is needed at all levels of fitness and ability to support the creation of muscle and act as a building block.
The IOM's guidelines were based on studies in sedentary individuals. The American College of Sports Medicine and the International Society of Sports Nutrition recommend aiming for more protein if you're active, up to 2 grams/kilogram of body weight each day to maintain muscle mass. While keeping protein within 10 to 35 percent of your daily calories still applies, experts recommend consuming 15 to 25 grams of protein within an hour post-workout (an example is 1 cup of milk, 1 ounce almonds and 5 dried apricots) to maximize results.
Does more protein equal better results? Not so, says current research, which suggests that benefits level off after recommended intakes. "It's kind of like adding laundry detergent to your clothes—it's not going to get them cleaner—but having the right amount, at the right time, is important," Crandall says.
Plus, the type of protein you choose could give you an athletic edge.
Foods high in a specific amino acid—the building blocks of protein—called leucine may be most effective for the maintenance, repair and growth of muscle. High-leucine foods include milk, soybeans, salmon, beef, chicken, eggs and nuts like peanuts. While you should strive to meet your protein needs from food, whey protein supplements are also high in leucine and are a research-backed option.
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As we age, our bodies become less efficient at transforming the protein we eat into new muscle. The result is gradual muscle loss that can lead to decreased strength, frailty and loss of mobility. But you can give Father Time a one-two punch by staying active and eating enough protein.
Two international study groups recommend that older individuals eat like young athletes: Keep your minimum daily protein intake to 1 gram/kilogram of body weight (68 grams and 80 grams for a 150-pound woman and a 180-pound man, respectively). And spread out your protein—about 25 to 30 grams of protein at each meal—since the amount of protein needed to trigger muscle maintenance is higher. Men and women aged 67 to 84 who ate the most protein and had the most even distribution across meals over two years had more muscle than those who fell short, per a 2016 American Journal of Clinical Nutrition study.
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"Protein needs rise a minimum of 10 grams per day during the second and third trimesters because your baby is growing—and it needs the tools to grow," says Rachel Brandeis M.S., R.D.N., who specializes in pregnancy nutrition. The IOM recommends that pregnant women eat a minimum of 1.1 grams/kilogram of body weight per day, or around 70 grams total.
Recent research suggests pregnancy protein needs may be slightly higher than these previous estimates, however, so it's best to check in with a doctor or registered dietitian to see how much protein is right for you.