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Protein is essential for building and maintaining muscle mass but consuming too much can negatively affect your health. Leah Flores/Stocksy
  • Protein is essential for building muscle, but health experts warn eating too much can pose health risks.
  • The current Recommended Daily Allowance (RDA) is 0.8 grams of protein per kilogram of body weight.
  • Endurance or strength athletes are recommended to take in 1.2 to 2 grams of protein per kilogram of body weight each day.

Protein may be a buzzword in wellness and body-building, but it’s also essential. So, in some ways, one nutrition expert doesn’t mind that people are paying attention to grams of protein on nutrition labels.

“Protein is the building block for muscles,” says Dr. Anupama Chawla, the director of the Division of Pediatric Gastroenterology and Nutrition at Stony Brook Children’s Hospital.

Indeed, research from 2018 indicates that muscle protein breaks down in the human body. Consuming more protein is essential to rebuilding — and even building more — muscle. As you might expect, consuming more protein than you take in is what helps build more muscle. And that’s part of the reason why people are honing in on the nutrient when purchasing food.

“It has become a fad because of the significant [focus] on weight loss and muscle building,” Chawla says. “It’s become an ‘in thing’ where everybody is reading the protein content.”

But pump the breaks before pouring an entire tub of protein powder into tomorrow morning’s breakfast smoothie. Experts and research indicate that there is such a thing as too much protein.

Though Chawla is happy protein is getting attention because of its importance to the human diet, she cautions against going to extremes, such as consuming an all-meat diet.

Too little is not good, and too much is not good,” Chawla says.

How much should you be consuming? That depends. Here’s what the research, health experts, and guidelines say.

The current Recommended Daily Allowance (RDA) is 0.8 grams of protein per kilogram of body weight.

“This means a person weighing 140 pounds only needs 51 grams of protein per day and another person weighing 200 pounds only needs 73 grams of protein per day, which is much less than “we are led to believe” by social media,” says Dana Ellis Hunnes, PhD, MPH, RD, a senior dietitian with UCLA Medical Center.

Trista Best, MPH, RD, a registered dietitian at Balance One Supplements, adds that this number equates to about 10 to 35% of our daily recommended caloric intake.

But, as with many aspects of medicine, there’s room for nuance. For example, age is one reason to up the protein intake.

“Older adults [around ages 65 to 70] should eat a little more, roughly 1 gram per kilogram or -.45 gram per pound of body weight because they don’t absorb quite as well and are more prone to muscle loss and bone fractures,” Hunnes says.

Some athletes also may require more to support their training regimen and physical activity.

For example, a 2016 position statement from the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and Athletic Performance recommended that:

  • physically active people take in 1.2 to 2 grams of protein per kilogram of body weight or 0.5 to 0.9 grams per pound of body weight, whether they are endurance or strength athletes.
  • base whether they consume the high or low end of these recommended amounts on intensity or working out or restricting calories
  • athletes consume 0.25 to 0.3 grams of protein per kilogram of body weight no more than two hours post-exercise to aid in increasing muscle.

Chawla agrees with these recommendations, with Chawla recommending anyone consuming 2 grams of protein per kilogram of body weight do so under the guidance of a medical professional to ensure the body, particularly the kidneys, continue to function correctly.

“This is because the kidneys have to work harder to eliminate the waste by-products from protein metabolism,” says Kimberley Rose-Francis, RDN, CDCES, CNSC, LD, a registered dietician nutritionist:

Hunnes strongly recommends consuming the lower end of the position’s statement, no more than 1.3 grams per kilogram per day.

“We can only absorb and utilize a certain amount of protein at any time,” Hunnes says. “More than that just turns into excess calories and eventually into fat. So, if we take in more than we need, we cannot use it, and it either goes to waste in our urine or becomes fat if we eat too many calories overall.”

The position statement was from 2016. What does more recent research point to?

Like Hunnes, a 2022 meta-analysis of 69 studies suggested sticking to the lower end of the position statement’s recommendations. Based on previous research, authors indicated that eating 1.5 grams of protein per kilogram of body weight, which equates to 0.7 grams of protein per pound, should be enough to build strength when combined with resistance training. The point about resistance training is a reminder that muscle mass is not simply a product of protein intake.

“If someone wants to build more muscle, they need to up the intensity of their strength training — higher weights, higher reps, or both — and break down their muscle fibers. Then, they need to eat a healthy diet,” Hunnes says.

A 2022 study of more than 4,800 Chinese individuals 60 and older suggested that male participants who consumed more than 78 grams per day and females who consumed 68 grams per day had the most protection against low muscle mass. They consumed less than 20 grams of protein per meal, and the majority of protein came from plant-based sources.

Another 2022 systematic review and meta-analysis of protein intake in healthy adults suggested that 1.6 grams of protein per kilogram of body weight per day could help individuals under 45 years old increase body mass slightly. People older than 45 only saw marginal increases.

A 2020 systemic review and meta-analysis of previous randomized control trials indicated that upping daily protein intake by up to 3.5 grams per kilogram of body weight over the course of several meals could help people grow or maintain muscle mass.

Consuming too much protein — over 2 grams per kilogram of body weight per day comes with risks, notes Rose-Flores, including:

  • kidney dysfunction
  • unwanted weight gain
  • increased risk for osteoporosis
  • azotemia

Research from 2020 indicates that high protein diets did not increase the risk for kidney or bone health but called for longer clinical trials. However, a “high protein diet” was classified as 1.07–1.60 grams of protein per kilogram of body weight, not 2 grams, as Rose-Francis indicated.

Additionally, Best notes that people consuming too much protein for their weight and activity level may experience the following:

  • irritability
  • dehydration
  • fatigue
  • nausea

Chances are, if you live in the US, you’re getting enough protein.

“If you’re eating a fairly varied diet, and you’re getting enough calories in this country — and you don’t have medical conditions such as protein-losing enteropathy or liver failure — you’re almost definitely getting enough protein,” Hunnes says.

What are the signs that you aren’t getting enough?

“An inadequate [amount of] protein can result in a weakened immune system, malnutrition, edema due to fluid imbalance, hair thinning, and muscle loss are some long-term complications resulting from inadequate protein intake,” Rose-Francis says.

Not surprisingly, research from 2019 indicates that people who do not consume enough protein have decreased muscle mass and strength.

“The best, or healthiest, sources of protein are those from lean animal meats or plants,” Best says. These include:

For vegetarians and vegans, plant-based proteins, like beans, tofu, and lentils, provide an alternative — but these sources are not always equivalent.

“There are 20 amino acids, nine of which are essential, meaning they are required to be taken in through the diet because the body cannot make them,” Best says. “Animal proteins have these nine already, which makes them complete proteins. However, not all plant sources are complete proteins.”

That doesn’t mean they aren’t beneficial or that you need to consume animal-based proteins to get adequate amounts to build or maintain muscle and overall health. You may just need to combine several sources of protein to keep the necessary amount.

“This sometimes means you’ll have to combine plant foods to get all nine essential amino acids. For instance, rice and beans combine to make a complete protein while quinoa is a complete protein in itself,” Best says.

What about all those protein bars and powders? Chawla isn’t a fan of the former.

“Some of these bars have 20 to 30 grams of sugar,” she says.

Chawla is more amenable to powders, particularly whey, for athletes needing more protein. But she cautions that everyone should refrain from being hyper-focused on protein for strength and overall health.

“People get stuck on protein sources and forget that they are not getting adequate calories from other sources,” she says, such as complex carbohydrates and produce.