Poll: High protein diets 'as risky as smoking'
Eating too much protein could be as dangerous as smoking for middle-aged people, a scientific study has found.
Research that tracked thousands of adults for nearly 20 years found that people who eat a diet rich in animal protein are four times more likely to die of cancer than someone with a low protein diet.
The risk is nearly as high that of developing cancer by smoking 20 cigarettes each day.
Previous studies have shown a link between cancer and red meat, but it is the first time research has measured the risk of death caused by regularly eating too much protein. Nutritional advice has traditionally focused on cutting down on fat, sugar and salt.
As well as red meat, dairy products high in protein are also dangerous, the researchers said. A 200ml (7fl oz) glass of milk represents 12 per cent of the recommended daily allowance, while a 40g (1.4oz) slice of cheese contains 20 per cent.
Chicken, fish, pulses, vegetables, nuts and grain are healthier protein sources. But a chicken breast or salmon fillet is still about 40 per cent of recommended daily protein intake.
The US study found that people with a high protein diet were 74 per cent more likely to die of any cause within the study period than their low-protein counterparts. They were also several times more likely to die of diabetes.
But this trend appeared to reverse for those aged over 65, researchers found.
"We provide convincing evidence that a high-protein diet – particularly if the proteins are derived from animals – is nearly as bad as smoking for your health," said Dr Valter Longo, of the university.
The researchers define a "high-protein" diet as deriving at least 20 per cent of daily calories from protein. They recommend consuming about 0.8g (0.03oz) of protein per kilogram of body weight every day in middle age. It means a person weighing nine stone should eat about 45-50g (1.6-1.7oz) of protein a day. A 300g (10.5oz) steak contains 77g (2.7oz) of protein.
"The research shows that a low-protein diet in middle age is useful for preventing cancer and overall mortality," said Dr Eileen Crimmins, a co-author of the study. "However, we also propose that at older ages, it may be important to avoid a low-protein diet to allow the maintenance of healthy weight and protection from frailty."
British expert
Dr Gunter Kuhnle, a food nutrition scientist at the University of Reading, said: "While this study raises some interesting perspectives on links between protein intake and mortality, it is wrong, and potentially even dangerous, to compare the effects of smoking with the effect of meat and cheese."
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