New scientific research has found that keeping to the high-protein diet could be as dangerous as smoking for middle-aged people, and is similar to smoking 20 cigarettes a day. The study made by the University of Southern California estimated that those who eat a diet rich in animal protein are four times more likely to die of cancer than someone with a low protein diet.
“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 study’s co-author Dr. Valter Longo, director of the Longevity Institute at the University of Southern California.
U.S. and Italian researchers tracked 6,318 adults over the age of 50 for about 20 years and discovered that protein-fans were 74 per cent more susceptible to early death from any cause than their low-protein counterparts. They were also several times more likely to die of diabetes.
However, the researchers claimed that plant-based proteins, such as those from beans, appeared to be beneficial and the outcomes were not linked to the amount of fat or carbohydrate in the diets – so they believe animal protein was to blame.
“Some proteins are better for you than others, for example plant-based proteins like beans. Vegans seem to do better in studies than those who eat animal based proteins. Red meat always comes out top as the worst and that’s probably due to its other components.”
“But the good news is that there is no evidence that fish is bad for you. So fish plus vegetables is really the best group of proteins,” added Dr. Longo.
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.
“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.”
This research doubts the long-term health effects of such popular diets like Atkins and Paleo that are know to be rich in protein. Instead, the researchers suggest people keep to a low-protein diet until old age when they start to lose weight and become frail, and then boost the body’s protein intake to stay healthy. They also recommend cutting down the amount of protein a day to no more than 0.8g for every kilogram of body weight, equivalent to 48g for a 60kg person, and 64g for an 80kg person.
In the over-65s, a high-protein diet cut the risk of death from any cause by 28%, and reduced cancer deaths by 60%, according to details of the study published in the journal Cell Metabolism. Protein levels controls the growth hormone IGF-I, which help bodies grow but high levels of which have been linked to cancer.
Nevertheless, there are those who find the results of the study, as well as the comparison with smoking rather controversial.
Heather Ohly, an Exeter University nutritionist, said: “Smoking has been proven to be entirely bad for us, whereas meat and cheese can be consumed in moderation as part of a healthy diet, contributing to recommended intakes of many important nutrients.”
Dr. Carrie Ruxton, an independent dietician and spokesman for the industry-funded Meat Advisory Panel, said the result may be due to those who ate non-animal protein getting more fibre from fruit and vegetables.