High protein diets such as Atkins, Dukan, South Beach, Miracle Metabolism and The Zone Diet have, for many
years, extolled the benefits of diets low in carbohydrates. Claiming that healthy meals should rather contain higher amounts of protein and, in some cases such as the Tim Noakes diet or the Paleo diet, fat.
However, a new study published in Cell Metabolism claims to show that high levels of protein (from animal sources) can in fact have severe negative health consequences in the long term.
In particular, adherents of these diets are apparently up to four times more likely to develop cancer and diabetes than those eating smaller amounts of protein.
The authors go as far as to suggest that eating a lot of protein (e.g. a diet based on eggs, milk, meat and cheese) increases the risk of cancer almost as much as smoking 20 cigarettes a day
Beans better than meat
The report also points out that these harmful effects were almost entirely eliminated if this protein was sourced from vegetables such as beans, instead of meat and dairy.
The study, which focused on a representative group of 6 381 people aged over 50, aimed to address the lack of long-term studies of the protein-rich diets which have been the subject of renewed popularity in recent years.
The lead author of the study, Valter Longo, suggests that to
prevent exposure to a high risk of diabetes and cancer, people should
eat no more than 0.8g of protein per kilogram of body weight a day. This is roughly equivalent to 48g for a 60kg person, and 64g for an 80kg person. You'll find about 21 g of protein in a 100g piece of chicken breast. Anything beyond this level is likely to increase the risk of illness.
In an interesting twist, however, this effect seemed to get reversed once an individual is over the age of 65. After passing this milestone, a high-protein diet was associated with improved health and a lower chance of developing serious illness.