Researchers analyzed survey data from 6,381 men and women aged 50 and above to understand the link between protein, certain diseases and mortality.
The study participants were split into three groups a high-protein group who ate 20 percent or more of their daily calories from proteins, a moderate-protein group who ate 10 to 19 percent of their calories from proteins and a low-protein group.
People between the ages of 50 and 65 who ate a high-protein diet had a 74 percent increase in overall mortality compared to those in the low-protein group. The meat lovers also had four-fold increased risk of dying from cancer during the study's 18 year follow-up.
However, this risk was only seen in those who got their protein from animal sources such as meat, eggs and cheese, the link disappeared if the protein came from plants, such as nuts, seeds and beans.
People who were over the age of 65 and ate a high-protein diet saw the opposite effect. Researchers saw a 28 percent reduction in death from all causes in this group. Cancer deaths in this older, high-protein group were also reduced.
Study participants of any age who ate a high-protein diet had a five-fold increased risk of dying from diabetes. Eating more than 10 percent of your calories from animal proteins in middle age could increase your risk of dying from diseases such as cancer and diabetes. But after 65, you may need that extra protein to protect your body from becoming frail. The majority of middle age is eating about twice as much protein as they should.
The Institute of Medicine's Food and Nutrition Board recommends eating about 0.8 grams of protein per kilogram of body weight every day in middle age. So a 160-pound person should eat about 55 to 60 grams of protein a day.