Proponents of the low-carb Paleo, ketogenic, and Atkins diets slammed the new study blaming high-protein diets for causing cancer and early mortality as inaccurate and misleading.
According to an 18-year study conducted by the University of Southern California, eating lots of animal protein and cheese quadruples cancer risk for middle-aged people and is as bad as smoking 20 cigarettes a day.
What's more, the study said people on high-protein diets were 74% more likely to die early than those who followed a low-protein diet. The study tracked 6,318 adults over the age of 50 for almost two decades.
"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.
The research was published March 4 in the medical journal Cell Metabolism, and has since stirred an avalanche of comments and finger-pointing, with the low-carb Atkins and Paleo diets bearing the brunt of the recriminations.
USC Study Did Not Control for Carb Intake or Sedentary Lifestyle
But Paleo diet advocates say the study confuses correlation with causation and doesn't take into account the amount of carbs the dieters in the study consumed. According to low-carb, high-fat (LCHF) proponents like Atkins, ketogenic and Paleo dieters, a high-carb diet — not a high-protein diet — is the cause of weight gain, cancer, heart disease, dementia, and early death.
If a person who followed a high-protein diet also ate lots of junky carbs, it's no wonder they got cancer and died early, said Paleos, who underscored that the Paleo diet does not encourage milk or cheese consumption.
Paleo proponents also pointed out that the quality of animal proteins you eats makes a huge difference in your health. Paleos avoid eating animals that have been injected with artificial growth hormones, opting instead for grass-fed beef, free-range chickens, and wild salmon. Eating factory-farmed meat and fish is what causes disease, they said.
Atkins diet followers also criticized the high-protein diet study, saying Atkins is not a high-protein diet, but a low-carb, high-fat, moderate-protein eating plan.
"High-protein consumption is not associated with all low-carb diets," Linda O'Byrne, chief nutritionist for Atkins, told The Grocer. "In fact, Atkins recommends taking 25% of calories from protein, which does not align with the diet in the study."
Contrary to widespread misconceptions, the Paleo and Atkins diets both recommend eating plenty of (non-starchy vegetables), in addition to high-quality animal proteins and fats. They are not all-meat diets.
LCHF Diets Shown to Prevent Diabetes, Cancer & Dementia
Meanwhile, more leading medical experts praise the low-carb, high-fat Atkins, ketogenic and Paleo diets for producing rapid weight loss without deprivation, reducing blood pressure, and preventing cancer, diabetes, heart disease, depression and Alzheimer's.
Neurologist Dr. David Perlmutter, author of Grain Brain, says a low-carb, high fat ketogenic diet prevents and even reverses Alzheimer's and ADHD. Cardiologist Dr. William Davis, author of Wheat Belly, said low-carb diets have been proven to reverse type 2 diabetes and heart disease.
And obesity expert Dr. Eric Westman, director of the Duke University Obesity Clinic, has seen thousands of patients experience dramatic weight loss on the low-carb, high-fat ketogenic and Atkins diets. These experts do not champion high-protein diets, but high-fat, low-carb diets.
"I tell my patients not to fear the fat," said Dr. Westman, author of New Atkins For a New You. "Eat lots of fat. Fat makes you feel full. There's no problem with fat. In fact, saturated fat — the fat that we've been taught not to eat — raises your good cholesterol best of all the foods you can eat."