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High-protein diets are touted as satiating and great for weight loss. But new research finds that they could do more harm than good if they’re not done smartly.

A new study from researchers at the University of Eastern Finland found that men who consumed a high-protein diet increased their risk of developing heart failure by 33 percent.

This finding comes as diets that tend to be higher in protein, like Atkins or keto, skyrocket in popularity.

A deeper look at protein

For the study, researchers gathered data on almost 2,500 men between the ages of 42 and 60 from 1984 and 1989. They asked the participants to log their food intake for four days and were followed over the course of 22 years. During that time, there were 334 cases of heart failure.

After more closely looking at diet, the researchers discovered that higher protein intake was correlated with greater risk of heart failure.

Further, researchers broke down the sources of protein intake. They found that the men who ate the most protein from animal sources had a 43 percent greater risk of heart failure compared with those who ate the least amount of protein.

Those that consumed a high amount of protein from dairy sources had a 49 percent increased risk. Those who consumed most of their protein from plants had a 17 percent increased risk.

Despite those higher protein intakes all being associated with increased risk for heart failure, protein from eggs and fish wasn’t associated with an increased risk.

Is your diet high protein?

“We studied the protein intake from a rather normal diet,” said study co-author Heli Virtanen, MSc, PhD student, and researcher at the Institute of Public Health and Clinical Nutrition at the University of Eastern Finland, Kuopio. She notes that the diets included in the study aren’t extreme, and therefore aren’t far off from how most people eat.

In fact, the group considered to be in the high-protein range was consuming an average of 19 percent of their calories from protein, 41 percent from carbohydrates, and 37 percent from fats.

The average daily protein intake of the men in the highest group was 112 grams. In the lowest group, protein intake was 76 grams.

To put that into perspective, around 3 ounces of chicken, turkey, pork, or ground beef would all have around 25 grams of protein.

What the experts say

Protein has become more and more popular with the rise of low-carbohydrate diets. But experts point out that too much protein can mean a diet that’s less balanced.

“Persons who consume high-protein diets become satiated quickly and often forego the other nutrients derived from ‘heart-healthy’ diets, including vegetables, legumes, whole grains,” said Dr. Benjamin J. Hirsh, director of preventive cardiology at Northwell Health’s Sandra Atlas Bass Heart Hospital in Manhasset, New York.

“In addition, many high-protein sources contain higher levels of saturated and trans fats, which have been clearly linked to heart disease,” he said.

Another potential explanation is that a large dietary protein content will raise blood sugar, as extra protein will be converted to glucose and stored, says Dr. Regina S. Druz, a cardiologist at the Integrative Cardiology Center of Long Island.

“Protein is composed of amino acids, which are the building blocks of muscles. But in excess, those may increase overall acidity, contributing to oxidative stress and therefore adversely impacting vascular function and myocardial contractility,” she said.

While the study showed that diets high in plant protein still detailed a slightly elevated risk of heart failure over diets that were generally low in any protein, Virtanen says people shouldn’t be worried.

“The association between plant protein intake and risk of heart failure lacked statistical significance,” she said. “This finding should thus not lead to too much concern, especially as previous studies have shown that plant protein has either no association with health risks or has an association with decreased risks.”

What this means for your diet

In fact, evidence from other studies shows that if you’re willing to decrease your carbohydrate intake, concentrating on plant protein and fat sources instead of animal sources could be more beneficial, says Virtanen.

More new research in the International Journal of Epidemiology echoes this concept. Scientists from Loma Linda University looked at heart health and protein intake of 81,337 men and women. Researchers found that those who consumed large amounts of meat protein had a 60 percent increase in cardiovascular disease. People who consumed a large amount of protein from nuts and seeds, on the other hand, actually had a 40 percent reduction in cardiovascular disease.

“This is in agreement with prior studies that showed a benefit to nuts and seeds,” Druz said. “The healthy saturated fats and the fatty acids in nuts and seeds may be protective, plus fiber content tends to be high.”

Druz warns that while high-protein diets are trending, only plant-based and Mediterranean diets have shown cardiac benefits. These diets include a high antioxidant content, nuts and seeds, fruits and vegetables, and moderate protein and fat intake.