High-Protein, Low-Carb Diet? It Can Be Risky

The Wall Street Journal—Research shows that a diet high in protein and low in carbohydrates can help shed pounds and normalize blood-glucose levels, improvements that lower the risk of diabetes and cardiovascular disease.

But will you live longer on a high-protein, low-carb diet? Two studies in the current edition of the scientific journal Cell Metabolism suggest the opposite. One involved an experiment conducted on mice, the other an 18-year study of humans who had divulged their dietary habits. Both studies found a strong association between longevity and a low-protein, high-carbohydrate diet, although the human study bore a twist: Beyond age 65, higher protein levels appeared to promote longevity.

“Those high-protein diets were developed with a shortsighted vision,” said Valter D. Longo, a University of Southern California professor of gerontology and biological sciences and the lead author of the human study. “On a high-protein, high-fat diet you can lose weight, but in the long run you may be hurting yourself.”

These studies are anything but definitive, showing only associations derived from highly limited evidence. But in gerontology, the influence of protein consumption on longevity is a hot topic. Last year, the American Federation for Aging Research hosted a symposium on “Optimal Protein Intake for Older Adults,” featuring a panel of scientists from academia and industry. No concrete answers emerged, except perhaps that protein consumption influences health in ways that are complex.

“High protein diets may be effective to lose weight rapidly,” said Elena Volpi, a professor of geriatrics at the University of Texas Medical Branch in Galveston. “But very high protein diets may also be harmful.”

Even then, though, the takeaway is somewhat complicated. Americans tend to consume the bulk of their protein at dinner, and the body isn’t always able to process an entire day’s worth in one sitting, said Dr. Volpi, who wasn’t involved in either study. “It appears you can better use the protein you need if you distribute it across three meals, especially if you are a senior,” she said.

One prominent diet expert and high-protein opponent, physician Ron Rosedale, saw the studies as vindicating his longtime warning about the risks of excessive protein. But Dr. Rosedale, who advocates a diet high in so-called healthy fats such as those found in avocados, argues that high levels of carbohydrate consumption are no less dangerous. “If people take these studies as a thumbs up for high carbohydrates, that’s missing the point,” he said.