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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
PUBLISHED : Wednesday, 05 March, 2014, 9:20pm
UPDATED : Wednesday, 05 March, 2014, 9:20pm
The Guardian in London
Consumers select meat products at a supermarket in Hefei, Anhui province. Photo: Xinhua
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 the National Health and Nutrition Examination Survey, which tracks a representative group of adults and children in the US.
The study 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.
For those over 65, a high-protein diet cut the risk of death from any cause by 28 per cent, and reduced cancer deaths by 60 per cent, according to details of the study published in the journal Cell Metabolism.
Professor Valter Longo, director of the Longevity Institute at the University of Southern California, said that on the basis of the study and previous work, people should restrict themselves to no more than 0.8 grams of protein a day for every kilogram of body weight, equivalent to 48 grams for a 60kg person.
"People need to switch to a diet where only around 9 or 10 per cent of their calories come from protein, and the ideal sources are plant-based," Longo said.
"We are not saying go and do some crazy diet we came up with. 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."
Study participants consumed an average of 1,823 calories a day, with 51 per cent coming from carbohydrates, 33 per cent from fat, and 16 per cent from protein, of which two-thirds was animal protein. Longo divided them into three groups.
The high-protein group got 20 per cent or more of their calories from protein, the moderate group got 10 to 19 per cent, and the low group got less than 10 per cent of their calories from protein.
"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 it was wrong "and potentially even dangerous" to compare the effects of smoking with the effect of meat and cheese, as the study does.
"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'?"
Heather Ohly at the European Centre for Environment and Human Health in Britain 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."
