Whether you’re trying to lose weight, gain muscle or stay strong and healthy as you age, protein is vital.
Protein is one of three macronutrients — along with carbohydrates and fat — that your body needs on a daily basis. Protein is the primary nutritional building block to build and repair tissue, says Donald K. Layman, professor emeritus in the department of food science and human nutrition at the University of Illinois.
Why You Need Protein
Registered dietitian Lora Edwards adds that protein is essential not just for our muscles, but also to develop and maintain healthy bones, skin and hair. She’s a clinical nutrition specialist at the Sports Medicine Center at Children’s Mercy Hospital in Kansas City, Missouri. “It’s also vital for our immunity and even makes up the hemoglobin that carries oxygen in your blood,” Edwards says.
Consuming enough protein is particularly important for older people, research suggests. Older adults who didn’t get enough protein “had significantly more functional limitations across all age groups,” according to a study of 11,680 people between ages 51 and up that was published online in February 2019 in the Journal of Nutrition, Health & Aging.
The importance of getting enough protein is clear. But how much protein is enough? The current recommended dietary allowance, or RDA, for adults is 0.8 grams per kilogram of an individual’s body mass (or 0.36 grams per pound of body weight). This is the minimum daily intake to prevent a deficiency.
Over the past decade, researchers found that increasing protein intake is safe and can help minimize muscle loss when cutting calories while dieting, says Chad Kerksick, director of the Exercise and Performance Nutrition Laboratory at Lindenwood University in St. Charles, Missouri. He’s also assistant dean of research and innovation at the university.
In 2015, a comprehensive review in Applied Physiology, Nutrition, and Metabolism suggests that eating a moderate amount — 25 to 35 grams — of high-quality protein during each meal “stimulates protein synthesis and promotes muscle health.” Consuming that amount also “plays a role in preservation of lean body mass with increasing age,” according to the research. The study also found evidence that increasing the proportion of dietary protein intake could help with weight and fat loss for some people with obesity on a certain eating regimen, and can help prevent weight regain.
[See: Top Plant-Based Proteins.]
The highest quality proteins include:
When it comes to how much protein you should consume, there’s no hard and fast guideline. Many individuals consume meals with 25 to 50 grams of protein. Eating more than 50 grams of protein per meal probably doesn’t provide any health benefits — but it won’t harm you either, says Layman.
How Protein Intake Impacts Kidney Function
There is a misconception that consuming more than 20 grams of protein in a single sitting would turn protein to fat, Layman says. Some physicians warn that excess protein intake can cause serious and potentially fatal damage to the kidneys. However, this idea is not supported by research, he says.
Some people who shift to a high-protein, low-carbohydrate diet may experience certain short-term effects, says Kate Patton, a registered dietitian with the Cleveland Clinic’s Center for Human Nutrition.
These effects include:
— A constant feeling of fullness.
It’s important for people shifting to a high-protein diet to make sure they drink enough water, which can help the body metabolize the protein and avoid these effects.
How Much Protein Your Body Needs
Your body will use “however much (protein) you eat — whether that’s 50 grams or 250 grams,” Layman says.
The only difference is how your body uses protein, Layman says. The body can only use so many amino acids (the building blocks of protein) for muscle protein synthesis, the process by which muscle cells repair and grow, he says. And muscle health and growth is the primary reason that people consciously increase their protein intake.
The amount of protein required for maximum muscle-building depends on a multitude of factors, explains board-certified sports dietitian and registered dietitian Marie Spano, lead author of the textbook “Nutrition for Sport, Exercise and Health.”
These factors include:
— Body size.
— Your training program and amount of muscle used.
— Total calorie intake.
— Overall health.
People who are larger and more active have greater protein requirements, as do those who are in a caloric deficit and want to prevent the body from breaking down existing muscle tissue for energy. Plus, after about the first 25 to 30 years of life, people naturally become less efficient at using the amino acids from protein to build muscle, meaning they need to eat more to get the same effect, Layman says.
To determine an individual’s ideal protein intake, the efficiency at which the body uses protein is an important consideration. Why? When it comes to using protein to build tissue, muscle cells don’t operate like an on/off switch. Instead, they act more like a dimmer, where, at a certain point, they gradually become less efficient at using each amino acid to build muscle tissue.
“You need a certain amount for protein to be effective at triggering muscle protein synthesis, and there is an increasing effect up to a certain point, but then the effect of each additional gram starts decreasing,” Layman says. “So, for example, you might get 90% of maximum efficiency with 25 to 30 grams, depending on the quality of the protein, then start to have decreasing efficiency after 50 grams.”
What Happens to Protein That Isn’t Used to Build Muscle
“We mostly talk about dietary protein in regard to muscle protein synthesis, but there are trillions of cells in the body that require protein,” Kerksick says. “It is needed for the healthy cell turnover and recovery in the organs, tissues — all of the cells within the immune system require protein.” Basically, muscle aside, protein serves as a primary structural component throughout the body, supporting all of the most basic physiological functions.
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Update 12/24/21: This story was previously published at an earlier date and has been updated with new information.