A high-protein diet like the meat-heavy Paleo diet is linked to cancer and early death among middle-aged people, according to a study published March 4 in the medical journal Cell Metabolism.
An 18-year study conducted by the University of Southern California indicates that eating lots of animal protein and cheese quadruples cancer risk for middle-aged people and is as bad for their health as smoking 20 cigarettes a day. The study tracked 6,318 adults over the age of 50.
What's more, people on high-protein diets were 74% more likely to die early than those who followed a low-protein diet. The research bolster claims that following a mostly vegetarian diet may be better for most people, especially those who are middle-aged.
Ironically, the high-protein diet had the opposite effect on Americans age 66 and older, whose cancer and mortality risk were better than senior citizens on a low-protein diet.
"We provide convincing evidence that a high-protein diet, particularly if the proteins are derived from animals, is nearly as bad as smoking," said Dr. Valter D. Longo, lead author of the study.
Some proteins are better for you than others, for example plant-based proteins like beans. Vegans seem to do better in studies than those who eat animal-based proteins. Red meat always comes out top as the worst and that's probably due to its other components. But the good news is there is no evidence that fish is bad for you. So fish plus vegetables is really the best group of proteins."
The research results are no surprise to Dr. David Katz, author of Disease-Proof. Dr. Katz, director of the Yale University Prevention Research Center, said getting enough high-quality protein in your diet is important, but it doesn't necessarily have to come from animal sources.
“The evidence is overwhelming and incredibly consistent that people who eat plant-based diets have a reduced risk of death," Katz told ABC News. “If you shift to a diet more about plant-based foods, you are likelier to live healthier and experience less chronic disease.”
Author and activist Dan Buettner agrees. In his bestseller The Blue Zones, Buettner said the longest-living and healthiest populations on the planet all follow a low-protein, mostly plant-based diet. "You don't need to become a vegetarian, but do bump up your intake of fruits and veggies," he said.