A study suggests that middle age people who are on high-protein diet are at greater risk of dying from cancer than those who favour a less protein-rich diet.
But not all researchers agree with the study's findings.
Morgan Levine at the University of Southern California in Los Angeles and her colleagues analysed a dietary survey of more than 6300 people in the US aged over 50.
Those aged 50-65 at the time of the survey and who had a high-protein diet - one where protein supplied a fifth of calories - were 75 percent more likely to have died over the next 18 years than peers who only got 10 percent of their calories from protein.
The high-protein eaters had a cancer death rate four times that of their low-protein peers. Statistical analyses showed that the findings only held for animal protein diets - in other words, protein from meat and dairy rather than beans and pulses.
But Tim Key, a Cancer Research UK epidemiologist based at the University of Oxford, said that the dietary survey is too small to provide any robust conclusions, New Scientist reported.
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Different health organisations recommend consuming different amounts of protein.
Study co-author Valter Longo, also at the University of Southern California said that people in middle age should try to eat at the lower end of these recommendations.