Restrict Protein, Not Just Calories, to Prolong Life

Recent research show that protein restriction may be far more effective  than calorie restriction in prolonging the lives of humans.  Many studies show that restricting calories prolongs the lives of yeast, worms, spiders, flies, insects, rats and probably monkeys.

Humans who severely restrict calories have long-life characteristics, such as low cholesterol and blood pressure and hearts that are more than 15 years younger than those of other North Americans their age (Experimental Gerontology, August 2007).

However, most of the test group of humans who restrict calories do not have a drop in a hormone called Insulin-Like Growth Factor-1 (IGF-1) that appears necessary for living a long time.  High blood levels of IGF-1 are associated with premature aging and diseases of aging such as diabetes and cancer.

IGF-1 levels are lower than normal in worms, flies and mice on restricted-calorie diets, but not in humans.

This week a report shows that IGF-1 shortens life by increasing cell DNA genetic damage, and causes cancer by blocking apoptosis that causes cancer
cells to kill themselves before they destroy their host (Science
Translational Medicine, February 16, 2011).

Luigi Fontana, a professor of medicine at Washington University in St Louis, noticed that most calorie-restricting humans eat high levels of protein, about 1.7 grams per kilogram of body weight/day.

This is more than the US government-recommended intake of 0.8 g/kg/day, and even higher than the 1.2 g/kg/day that the average American eats.  Dr. Fontana asked humans on calorie restricted diets to reduce their intake of protein to 0.95 g/kg/day.

After just three weeks of reduced protein intake, their IGF-1 levels dropped markedly (Aging Cell, September, 2008). Among the calorie-restricting humans, vegans have lower levels of IGF-1 than meat-eaters (Rejuvenation Research, February 2007).

Strict vegans also have significantly lower IGF-1 levels than people who restrict just calories, even if they are heavier and have more body fat.
Strict vegans take in about 10 percent of their calories from protein, whereas those on calorie restriction tended to get 24 percent of calories from protein. Read the rest of this entry »