high animal protein diet apparently not healthy

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

Instead, it 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.

Teasing out the health effects of individual nutrients is notoriously difficult. 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. Other factors can skew results too: a person on the study who got ill might have gone off their food, and seen a proportional rise in the amount of calories they get from protein. In that case, it would be the illness driving the diet, not the other way round.

"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," said Peter Emery, head of nutrition and dietetics at King's College London.

Gunter Kuhnle, a food nutrition scientist 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 Exeter 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."

eating steak and dairy is as harmful as smoking? Give me a break ....

if this is true, then I am screwed...

"People need to switch to a diet where only around nine or ten percent of their calories come from protein, and the ideal sources are plant-based," Longo told the Guardian.