Too much meat and cheese is as bad as smoking, US study suggests
US study suggests the over-consumption of meat, eggs, milk and cheese by the middle-aged can quadruple the risk of cancer and diabetes
A diet rich in meat, eggs, milk and cheese could be as harmful to health as smoking, according to a controversial study into the impact of protein consumption on longevity.
High levels of dietary animal protein in people under 65 years of age was linked to a fourfold increase in their risk of death from cancer or diabetes, and almost double the risk of dying from any cause over an 18-year period, researchers found. However, nutrition experts have cautioned that it was too early to draw firm conclusions from the research.
The overall harmful effects seen in the study were almost completely wiped out when the protein came from plant sources, such as beans and legumes, though cancer risk was still three times as high in middle-aged people who ate a protein-rich diet, compared with those on a low-protein diet.
But whereas middle-aged people who consumed a lot of animal protein tended to die younger from diseases, the same diet seemed to protect people's health in old age.
The findings emerged from a study of 6,381 people aged 50 and over who took part in a nutrition survey in the US.
The study published in the journal Cell Metabolism suggests people should eat 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.
Professor Valter Longo, director of the Longevity Institute at the University of Southern California, said: "People need to switch to a diet where only around nine or 10 per cent of their calories come from protein, and the ideal sources are plant-based," Longo said.
"If we are wrong, there is no harm done, but if we are right you are looking at an incredible effect that in general is about as bad as smoking."
"I would urge general caution over observational studies, and particularly when looking at diet, given the difficulties of disentangling one nutrient or dietary component from another," said Professor Peter Emery, head of nutrition at King's College in London.
"You can get an association that might have some causal linkage or might not."
Dr Gunter Kuhnle, a nutritionist at Reading University, said: "Sending out [press] statements such as this can damage the effectiveness of important public-health messages. They can help to prevent sound health advice from getting through to the general public. The smoker thinks: 'Why bother quitting smoking if my cheese and ham sandwich is just as bad for me?'"