Protein intake has been a bit controversial in recent years—while it sounds like a good idea to eat a protein-rich diet, studies have found that too much protein, especially from certain sources, is not so good for long-term health. A new study from the University of Eastern Finland finds that men who eat a high-protein diet have a slightly increased risk of heart disease in middle age. But again, not all proteins are created equal.
The findings were published in American Heart Association journal, Circulation: Heart Failure.
The researchers looked at data from a group of 2,440 middle-aged men, who varied in their protein intake. They were followed for an average of 22 years, which is a fairly long time as studies go. The team divided the men up into four groups, from lowest to highest protein intake, and correlated this with cardiac events, of which there were 334 during the study period. They also looked at whether and how the type of protein might affect heart risk.
It turned out that protein intake was significantly linked to heart risk, and the type mattered, as with previous studies. For men in the highest overall protein intake group, their risk of heart failure was 33% higher than men with the lowest intake. For animal protein, the risk was 43% higher; for dairy protein, 48% higher; and for plant protein, it was 17% higher. But it’s important to mention that for plant protein, the relationship was not statistically significant, meaning that they could have been due to chance. (And for total animal protein, the link was barely significant.)
Protein intake from fish and eggs were not associated with an increase in heart risk, which may suggest that the respective health benefits of these sources outweigh the risks. Fish, with its omega fats, is known to benefit heart health, and eggs have recently been shown to be linked to reduced heart risk, or at least to not be so bad as we once thought.
“As many people seem to take the health benefits of high-protein diets for granted, it is important to make clear the possible risks and benefits of these diets,” said study author Jyrki Virtanen. “Earlier studies had linked diets high in protein — especially from animal sources — with increased risks of Type 2 diabetes and even death.”
That’s certainly true. A few years ago, a study found that eating a high-protein diet was linked to an increased risk of cancer, diabetes, and mortality. Middle-aged participants who ate moderate-protein and high-protein diets were three and four times more likely to die of cancer, respectively, compared to those who ate low-protein diets. And people who ate high-protein diets were 75% more likely to die from any cause, including three times as likely to die from diabetes. The team calculated that high-protein diet presented similar a similar level of cancer risk to smoking. Most of this risk was accounted for by animal protein, however—veggie proteins didn’t seem to carry the same danger.
Another study a few years ago found that among women who lost weight, and whose insulin levels should have improved, their insulin levels didn’t improve, which may be due to their higher protein intake. Others have found protein—again, animal, not vegetable—linked to early mortality. And finally, another recent study hinted that animal protein may be linked to heart risk in older women. The new study offers a nice complement, as it looks specifically at men.
The current study was small, however, and more work will be needed to understand more fully the risk for both sexes at various ages. But the research in the field has been pretty convincing so far. And as many experts have said, protein from plant sources, including vegetables, nuts, beans, and legumes seems best. And for animal protein, it’s likely wise to keep it at a minimum, making it an exception in our diets rather than the rule.