Researcher Valter Longo, of the University of Southern California’s Longevity Institute, said that people should be more aware of the amount of protein they eat. “Spend a couple of months looking at the labels on your food. There is a little bit of protein everywhere.”
Longo told The Daily Telegraph: “We provide convincing evidence that a high-protein diet – particularly if the proteins are derived from animals – is nearly as bad as smoking for your health.”
The scientists drew their conclusions from a study of 6,381 people aged 50 and over who took part in the National Health and Nutrition Examination Survey (NHANES) in the US.
A link between high protein intake and raised levels of the growth hormone IGF-1 might be a possible cause for the raised mortality rate. However, the health risks almost disappeared when the main source of dietary protein was plant-based. Longo said that only around ten per cent of the calories we consume should come from protein, and “the ideal sources are plant-based”.
The survey recommends a protein intake of no more than 0.8 g per kg of body weight per day during middle age (e.g. 51 g for a person weighing 10 stones, 61 g for a person weighing 12 stones). The British Nutrition Foundation provides similar figures, noting that the daily protein requirement is 45 g and 56 g for the average woman and man respectively. It notes that most people eat far more protein than they need, with average intakes around 88 g per day for men and 64 g per day for women. The findings call into question the long-term safety of the Atkins and Paleo diets which recommend high intakes of meat and other animal proteins.
Read the survey here.