Washington: Two groups of researchers have claimed in two different studies that consuming high-quality animal protein in moderation is one of the keys to a long and healthy life.
The first study suggests that consuming moderate to high levels of animal protein prompts a major increase in cancer risk and mortality in middle-aged adults, while elderly individuals have the opposite result.
Meanwhile, the second team of researchers found that a high-protein, low-carb diet led to a shorter lifespan in mice. Both studies find that not all calories are created equal-diet composition and animal protein intake are key players in overall health and longevity.
University of Southern California's Dr. Valter Longo , who is the senior author of one of the papers, said that the team studied mice and humans and provide convincing evidence that a high-protein diet-particularly if the proteins are derived from animals-is nearly as bad as smoking for health.
By analyzing information on 6,831 middle-aged and older adults participating in NHANES III, a nationally representative dietary survey in the US, Longo and his team found that individuals aged 50 years who reported eating a high-protein diet were 4 times more likely to die of cancer or diabetes and nearly twice as likely to die from any cause in the following 18 years.
Also, a moderate-protein diet was associated with a 3-fold increase in cancer mortality. These effects were either abolished or reduced in individuals eating a high-protein diet that was mainly plant based.
For people older than 65 years, however, the effects on mortality were reversed: those who consumed high amounts of protein had a 28 percent reduced risk of dying from any cause and a 60 percent reduced risk of dying from cancer. Similar beneficial effects were observed for the moderate-protein-intake group.
The researchers found that the effects of protein on an individual's risk of dying may be caused in part by the activation of growth hormone and the growth factor IGF-1.
Notably, the activity of these factors, but also body weight, declines naturally with aging, which may explain why older people not only did not benefit but appeared to do worse if they ate a low-protein diet, Longo explained.
In the second study by Simpson's group in Australia conducted in hundreds of mice on 25 different diets, investigators who examined the effects of protein, fat, and carbohydrate on energy intake, metabolic health, aging, and longevity found that a high-protein, low-carbohydrate diet resulted in reduced food intake and body fat, but it also led to a shorter lifespan and poor cardiometabolic health.
A low-protein, high-fat diet had the most detrimental effects, while a high-carbohydrate, low-protein diet was best, resulting in longer lifespan and better cardiometabolic health, despite also increasing food intake and body fat.
The investigators predict that a diet with moderate amounts of high-quality protein that is also relatively low in fat and high in complex carbohydrates will yield the best metabolic health and the longest life.
The study is published in the Cell Press journal Cell Metabolism.
