Diet rich in animal protein could be as bad as smoking: US study

LONDON — A diet rich in meat, eggs, milk and cheese could be as harmful to health as smoking, according to a study released this week.

The study, which involved 6,381 people aged 50 and above who were surveyed in the United States, found that high levels of dietary animal protein in people under 65 was linked to a four-fold 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.

These risks were cut when protein came from plant sources such as beans, though cancer risk was still three times as high in middle-aged people who ate a protein-rich diet.

Conversely, the study also found that animal-protein-rich diets in those above 65 cut the risk of death from any cause by 28 per cent, and reduced cancer deaths by 60 per cent.

The results were published in the journal Cell Metabolism.

Dr 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 0.8g of protein a day for every kilogramme of body weight — equivalent to 48g 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,” Dr Longo told the Guardian. “If we are right, you are looking at an incredible effect that, in general, is about as bad as smoking.”

However, nutrition experts have cautioned that it is too early to draw firm conclusions from the research.

The apparently harmful effects of a high-protein diet might be down to one or more other substances in meat, or driven by lifestyle factors that are more common in regular red meat eaters versus vegetarians.

Said Dr Peter Emery, Head of Nutrition and Dietetics at King’s College London: “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. You can get an association that might have some causal linkage or might not.” THE GUARDIAN