High-Protein Diet 'Risky as Smoking' for Middle-Aged But effects were reversed among over-65s By Rob Quinn, Newser Staff Posted Mar 5, 2014 2:21 AM CST 26 comments Comments People between 50 and 65 should cut down on animal protein if they want to live longer, researchers say. (Shutterstock) (Newser) – Good news and bad news for meat lovers: People who eat a diet high in protein in middle age are a staggering four times more likely to die of cancer than people on a low-protein diet, according to new research, but people over 65 who consumed more protein were less likely to die of cancer. The study, which tracked 6,000 people over 18 years, found that people between 50 and 65 with a diet rich in animal protein were 75% more likely to die of any cause over the study period as well as much more likely to die of cancer, Scientific American reports. But for the elderly, higher protein intake helped fight off frailty. "Your stage in life matters," the lead researcher tells the Los Angeles Times. "Some have said for years that proteins are bad. That’s half right and half wrong." The researchers believe the link between protein consumption and cancer is related to a growth hormone stimulated by high protein consumption, reports LiveScience. The source of protein mattered for the middle-aged people studied, with the risk of cancer going down steeply in those who consumed mainly plant-based proteins instead of animal proteins, though the beneficial effects of protein for the elderly weren't affected by the source.