Protein Intake Linked to Lifespan

Two new studies find that low protein intake may help increase lifespan and lower the risk of diseases such as cancer and diabetes.

The first study, led by researchers at the University of South California, showed that high protein consumption is linked to increased risk of cancer, diabetes, and death in middle-aged adults, although this was not the case for older adults who may benefit from moderate protein consumption.

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Investigators analyzed data on more than 6,800 American adults who took part in the National Health and Nutrition Examination Survey (NHANES) III, a U.S. national survey that assesses health and diet. They found that participants age 50 and above who reported eating a high-protein diet were 4 times more likely to die from cancer or diabetes, and twice as likely to die from other causes, in the following 18 years. Those who consumed moderate amounts of protein were 3 times more likely to die of cancer.

These effects either disappeared or were lessened in participants whose high-protein diet was mostly plant-based, according to the authors, who note the effects were nearly the opposite among participants age 65 and older. For example, high protein intake was linked to a 60 percent lower risk of death from cancer, and a 28 percent reduced risk of dying from any cause, with similar effects seen in those with moderate protein intake.

The second study, led by Stephen Simpson, a professor at the University of Sydney in Australia, trialed the effects of 25 different diets on hundreds of mice to see how different amounts and types of proteins, fats, and carbohydrates affected energy intake, metabolic health, aging, and lifespan.

The team found that mice on diets high in protein and low in carbohydrates had reduced food intake and lower levels of body fat. However, these mice also died earlier and had worse cardiometabolic health. In addition, mice on low-protein, high-fat diets experienced the poorest health and shortest lifespans, while the healthiest, longest-living mice were those on diets rich in carbohydrates and low in protein.

“A consensus is beginning to emerge that diets rich in fruits and vegetables, but low in animal protein-based and processed foods rich in simple sugars, is healthy for most people,” says Brian K. Kennedy, PhD, CEO, and professor at the Novato, Calif.-based Buck Institute for Aging, and a co-author of the USC-led study.

“Of course,” he says, “we all age in a personalized manner that depends on genetics as well as levels of exercise and other factors. So, what is right for one person may not be optimized for the next.”

Kennedy describes the USC finding that associated protein intake with reduced mortality in older individuals as “a surprise,” adding that “clearly more research needs to be performed to understand why humans go through this transition in optimum nutrition with age.”

—Mark McGraw

References

Levine M, Suarez J, et al. Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population. Cell Metabolism 2014.

Solon-Biet S, McMahon A, et al. The Ratio of Macronutrients, Not Caloric Intake, Dictates Cardiometabolic Health, Aging, and Longevity in Ad Libitum-Fed Mice. Cell Metabolism. 2014.