Protein is an important macro nutrient and plays a major role in various physiological conditions. The requirement of protein depends on the body and other factors such as size, age and gender. Low protein diet may lead to diseases such as protein energy malnutrition, so an individual who does not follow an intense exercise routine should only consume moderate amounts of protein, which is 15 to 20% of total calories according to the ideal body weight.
Middle aged people with high protein content in their diet are more likely to die from cancer than those who eat less protein, found a study.
However, for people older than 65, a moderate protein intake may actually be beneficial, and protect against frailty, the researchers said.
"Popular diets in many cases have high protein and low sugar content. They may make you lose weight, but that's not a good diet to increase life span," said study researcher Valter Longo, professor of biology at the University of Southern California (USC) and director of the USC Longevity Institute.
The risks of a high-protein diet are even comparable to smoking, the researchers said. People who smoke are four times more likely to die of cancer compared with non-smokers, Longo said.
The reason behind a high protein diet’s link to cancer is because protein controls the growth hormone IGF-I (insulin growth hormone), which helps our bodies grow but has been linked to cancer susceptibility. IGF-1 exerts powerful effects on each of the key stages of cancer development and behavior: Levels of IGF-I drop off dramatically after age 65, leading to potential frailty and muscle loss. The study shows that while high protein intake during middle age is very harmful, it is protective for older adults: those over 65 who ate a moderate to high-protein diet were less susceptible to disease.
Although, plant based proteins do not seem to have the same mortality effects as animal proteins.
So, “a low-protein diet in middle ages is useful for preventing cancer and overall mortality, through a process that involves regulating IGF-I and possibly insulin levels," said co-author Eileen Crimmins, the AARP Chair in Gerontology at USC.