When you go overboard on protein, this is what can happen in your body

By Jacqueline Howard, CNN

(CNN) — There’s one buzz word that you might be hearing a lot lately: protein.

Whether it’s Starbucks testing a protein-packed cold foam or reality TV star Khloé Kardashian launching her own brand of protein popcorn, the macronutrient is having a cultural moment – and rightfully so. Protein is an important part of a healthy diet.

Along with carbohydrates and fat, protein is one of the main macronutrients that make up our diet. It’s also the only macronutrient that supplies us with amino acids.

When our bodies digest protein in food, it gets broken down into amino acids, which have a hand in many bodily processes, such as building and preserving muscle, making hormones, boosting the immune system and even maintaining healthy hair, skin and nails.

But some nutrition scientists warn that thanks to social media trends, many people may be consuming too much protein.

“When you eat more protein than your body needs, your body can’t store the extra. It just gets rid of it in urine or turns it into energy or fat,” said registered dietitian Dr. Michelle Cardel, chief nutrition officer at WeightWatchers and adjunct professor at the University of Florida.

For most healthy people, this isn’t necessarily harmful, she said, but “once you’ve had enough protein, you’ve met your needs. More protein doesn’t equal more benefit, whereas balancing protein with fiber intake is going to be really important when thinking about longevity and optimizing health and well-being across the lifespan.”

In some cases, going overboard on protein and not balancing it with fiber could lead to weight gain or digestive problems.

“One of the common signs is constipation,” said Dr. David Liska, chair of the Department of Colorectal Surgery at the Cleveland Clinic.

“Constipation can lead to a whole slew of other complaints,” he said, adding that’s why having a diet that’s high in fiber is important. “We generally recommend about 25 to 35 grams of fiber a day for overall gut health – that should be accompanied by a lot of water intake.”

Balancing protein and fiber

The recommended dietary allowance (RDA) for both men and women is about 0.8 grams of quality protein per kilogram of body weight, which is equivalent to about 0.36 grams per pound.

Established jointly by the US Department of Agriculture and the US Department of Health and Human Services, the RDA represents the minimum amount of a nutrient that must be eaten by a relatively sedentary person to meet their basic needs.

“So for somebody who weighs 150 pounds, aiming for about 68 grams [of protein] is more than sufficient,” Cardel said.

She added that protein needs can shift, depending on your age or weight loss goals.

“People who are aiming to lose weight, particularly if they’re on a GLP-1, which is going to result in rapid weight loss, should aim for at least 1 gram [of protein] per kilogram of body weight daily,” Cardel said.

“Protein alone isn’t going to be that main driver of muscle maintenance or gain,” she said. “Protein supports the process, but consistent resistance training is truly what’s going to build and maintain muscle.”

While protein plays an important role in supporting strength and development in the body, fiber is important for digestion and helping to prevent diseases.

In the United States, it’s estimated that more than 90% of women and 97% of men do not meet recommended intakes for dietary fiber, according to the 2020-2025 Dietary Guidelines for Americans.

There are two types of dietary fiber: soluble and insoluble.

Soluble fiber is more associated with some of the digestive benefits of fiber. It absorbs water to form a gel-like substance during digestion. Soluble fiber can be found in oat bran, barley, nuts, seeds, beans and some fruits and vegetables.

Insoluble fiber, on the other hand, doesn’t dissolve in water and helps people have more frequent and heavier bowel movements. It can be found in foods such as wheat bran, vegetables and whole grains.

Some research suggests that eating the right balance of protein and fiber can help maintain a healthy weight or even support weight-loss goals.

A small study published last year in the journal Obesity Science and Practice followed people trying to lose weight and found that those who were the most successful at shedding pounds increased their consumption of both protein and fiber while cutting back on calories.

“Protein and fiber densities were inversely associated with weight loss,” the researchers, from the University of Illinois Urbana-Champaign, wrote in the study.

The 30/30/30 rule

To ensure that she gets an adequate balance of both protein and fiber in her daily diet, Cardel said follows a specific rule.

“I tend to think about my health in a 30/30/30,” she said. “At least 30 grams of protein per meal, at least 30 grams of fiber daily and at least getting 30 minutes of physical activity every day – and that helps keep me balanced.”

So what are some ways to add healthy amounts of protein and fiber to your diet?

One egg contains 6 grams of protein, one half-cup of cottage cheese offers 14 grams, and one Greek yogurt can have up to 18 grams. So a breakfast that includes all these things would give you about 38 grams of protein within your first meal of the day.

For fiber, one half-cup of unsweetened bran cereal has about 14 grams, and one cup of raspberries has about 8 grams.

And for snacks that are high in both protein and fiber, go for beans. A half-cup of edamame has about 8 grams of protein and about 4 grams of fiber.

To hit a healthy balance of protein and fiber intake, Liska said recommends following a Mediterranean diet.

“A Mediterranean diet is one of these very balanced diets. It’s still high in protein but also high in fruits and vegetables, olive oil,” he said. “If you follow a Mediterranean diet with that balance of protein and vegetables and fats, that has usually been found to be associated with good gut health, good cardiovascular health and also a decreased risk of colorectal cancer.”

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CNN’s Kristen Rogers and Andrea Kane contributed to this report.