Higher Protein Intake Linked to Lower Risk of AF

Marlene Busko

April 03, 2020

New data from the Women's Health Initiative show that those who ate more protein in proportion to their weight were slimmer and less likely to develop atrial fibrillation (AF) over the next decade, researchers report.

The study, by Daniel A. Gerber, MD, a cardiology fellow at Stanford University, California, and colleagues, was presented at the virtual American College of Cardiology 2020 Scientific Session (ACC.20)/World Congress of Cardiology.

During a press briefing, Gerber said their findings suggest that "eating more protein (specifically more protein compared to your body weight) — not necessarily going out and eating a whole lot more food, but maybe shifting your dietary intake toward a higher percentage of protein — can have these positive impacts both on body composition and risk of atrial fibrillation."

For heart health, "I would recommend a diet focused on reducing processed foods and added sugars that are loaded with empty calories, carbohydrates, and fats, while maintaining a proportionally higher protein intake from healthy sources, including lean animal proteins and plant-based sources," Gerber told theheart.org | Medscape Cardiology in an email.

Gerber explained that the average American eats an estimated 3600 calories/day — 50% from carbohydrates, 35% from fat, and only 15% from protein.

This translates to 540 calories per day from protein, which is 135 g (since 1 g of protein has 4 calories), "which is more than enough protein for the average person."

"There does appear to be a 'sweet spot' with regard to protein intake, at around 58 to 74 grams per day, along with a 'ceiling effect' above 74 grams per day, where more protein intake is no longer beneficial," he said.

According to Gerber, "most people would be far healthier and leaner by reducing their total caloric intake from carbohydrates and fats while eating a proportionally higher protein diet closer to 25% of their total calories."

Plant-based Protein Appears More Beneficial

"The vast majority of folks in the Western world probably consume too much protein already," Andrew M. Freeman, MD, director of Cardiovascular Prevention and Wellness, National Jewish Health, Denver, who was not involved with this study, told the theheart.org | Medscape Cardiology in an interview.

"It's certainly an intriguing study," said Freeman, who is co-chair of the ACC Nutrition and Lifestyle Workgroup, "but I didn't walk away saying 'Gee whiz, I've got to start forcing protein in large quantities in my patients,' because they are already taking too much and we know that too much protein intake is linked to increased incidence of kidney dysfunction, heart failure, and a variety of other issues including cancer."

Nevertheless, lower body mass index (BMI) is associated with lower risk for AF, he noted, "and if 8 to 10 grams of additional protein helps people maintain their body weight, that's great."

"I just hope that they would choose a more plant-based source for this protein," Freeman said.

Based on recent literature, "it appears that plant-based proteins appear to be quite beneficial and helpful for anti-inflammatory properties and lower cholesterol — things like soy and almonds — and animal-based proteins, which are usually accompanied by a variety of other bad things, like a lot of extra cholesterol or fats, sometimes seem to worsen things."

He recommends that people should "do their best to maintain a normal BMI and eat a diet that is predominantly, if not totally, plant-based, including protein," which appears to be the diet that is the most anti-inflammatory and best for lowering the risk for atherosclerosis and cancer.

Protein and AF in Women's Health Initiative

According to current US guidelines, the recommended dietary allowance (RDA) for protein is 0.8/kg of body weight per day, which for a 140-pound person is about 51 g of protein a day, the researchers explain.

To examine how protein intake might affect risk for AF, they analyzed data from 99,554 women in the Women's Health Initiative.

Protein intake was based on replies to food questionnaires, and urine nitrogen levels were used to validate this. Physical activity levels were also based on self-report.

The women had a median age of 64 years; most were white, but 8.3% were black, 2.9% were Hispanic, and 2.2% were Asian.

Their median protein intake was 66 g/day or 0.9 g/kg body weight per day.

During a mean follow-up of 10 years, 21,258 women (21.3%) developed AF.

Compared with women in the lowest protein-intake quartile (<58 g/day), women who consumed 58 to 66 g/day of protein had a significantly lower adjusted risk for incident AF (hazard ratio [HR], 0.932; = .001) than did women who consumed 66 to 74 g/day (HR, 0.908; = .0005).

Expressed differently, women with an intermediate protein intake had a 7% to 8% lower risk for incident AF than women with the lowest protein intake.

In contrast, women in the highest protein-intake quartile (>74 g/day) did not have a significantly lower risk of AF (HR, 0.951; = .186).

The hazard ratios were adjusted for age, ethnicity, education, physical activity, BMI, tobacco and alcohol use, hypertension, hyperlipidemia, diabetes, coronary and peripheral artery disease, and heart failure.

To go from low to intermediate protein intake is "not a huge amount," Gerber said in a statement issued by the ACC.

"We're talking about eating 10 to 20 more grams of protein per day; that's only four ounces of healthy protein, such as chicken breast or salmon, a cup of Greek yogurt, or two eggs."

"Of course, when we talk about increasing protein intake, it needs to be with heart-healthy foods and lean proteins, not with cheeseburgers and other foods that are high in saturated fat, cholesterol, and sugar," he cautioned.

The study did not receive any external funding, and the researchers and Freeman have no conflicts of interest to disclose.

American College of Cardiology (ACC) 2020 Annual Scientific Session/World Congress of Cardiology. Released March 19, 2020.

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