Too much protein as bad as smoking?

Whether you follow one of the many low-carb/high-protein diets, frequent the gym for some "massive gains", or simply enjoy eating meat and cheese, there is one thing in common: lots of dietary protein. Although high-protein diets can help build muscle in the short-term, few studies have been done to show the effects in the long-run.

A study published on March 4th shows that too much protein consumption in middle aged people can have devastating long-term effects. In people aged 50-65, those who reported eating high amounts of protein (20% of calories from protein) had a 75% increase in mortality and 4 fold increase in risk of cancer death in the following 18 years; these effects are comparable to those of smoking! Outcomes were especially bad when proteins were derived from animal sources like meat, eggs, and cheese, but not as bad when from plant sources. However, in participants over the age of 65, higher protein consumption helped to lower these risks. 

Why does high protein have different effects in different age groups? The scientists think that this is linked to a growth hormone in the body called IGF-1, which increases with higher protein consumption. High levels of IGF-1 helps the body to grow but may also increase the risk of cancer. Older individuals have naturally lower amount of IGF-1, so eating more protein can help lower mortality as well as preserve muscle mass. 

The long-term effects of high protein diets are not quite conclusive, and this study has several weaknesses which may limit its applicability. However, with a growing body of evidence supporting the risks of a high-protein diet, we may want to think twice before we load up on meats, eggs, and cheese. 

Just some food for thought.

1.

Levine ME, Suarez JA, Brandhorst S, Balasubramanian P, Cheng C-W, Madia F, et al. Low Protein Intake Is Associated with a Major Reduction in IGF-1, Cancer, and Overall Mortality in the 65 and Younger but Not Older Population. Cell Metabolism. 2014 Mar;19(3):407–17.