Are you middle-aged and partial to cheeseburgers? If so, you may be concerned by a study suggesting you have a much greater risk of dying from cancer than your peers who favour a less protein-rich diet. But not all researchers agree with the study鈥檚 findings.
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 鈥� one where protein supplied a fifth of calories 鈥� were 75 per cent more likely to have died over the next 18 years than peers who only got 10 per cent 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 鈥� in other words, protein from meat and dairy rather than beans and pulses.
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In a follow-up study in mice, the team also found that animals fed a low-protein diet had a lower incidence of cancer than those on a high-protein diet. The low-protein mice that did develop the disease had slower-growing tumours.
Lots of leaps
But , a Cancer Research UK epidemiologist based at the University of Oxford, says the dietary survey is too small to provide any robust conclusions.
Catherine Collins, chief dietician at St George鈥檚 Hospital, London, doesn鈥檛 dispute the results in mice, but says the authors make a lot of leaps when trying to apply the findings to humans. What鈥檚 more, the conclusions are based on a single survey of what people reported eating in the preceding 24 hours. 鈥淎s a dietician that鈥檚 worrying,鈥� she says. 鈥淭here are so many errors with the data collection. It implies people鈥檚 diet doesn鈥檛 change over 18 years.鈥�
Study co-author Valter Longo, also at the University of Southern California, counters that the participants said that the 24 hour period was representative of their diet. 鈥淢ost people don鈥檛 change their diet very often,鈥� he says.
Different health organisations recommend consuming different amounts of protein. Longo says that people in middle age should try to eat at the lower end of these recommendations.
Collins isn鈥檛 convinced. 鈥淲e don鈥檛 need to do anything different, and nor should we be worried [on the strength of this study],鈥� she says.
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