Research recently published in the journal Cell Metabolism suggests a high-protein, low-carbohydrate diet may shorten life span.
In the study, the researchers fed 858 mice 25 different diets with various ratios of protein, fat, carbs and energy density. The researchers found that, in mice, a high-protein, low-carb diet led to lower body fat and overall food consumption, but also a shorter life span. Conversely, a high-carb, low-protein diet resulted in a longer lifespan and better cardiometabolic health, but increased food intake and levels of body fat. A low-protein, high-fat diet was said to have "the most detrimental effects,"according to this press release.
If the study results are valid for humans, a high-protein, low-carbohydrate diet might make you look healthy, but it won't help you live longer. On the other hand, a high-carb, low-protein diet could leave you with more body fat, but you'll be more likely to outlive the high-protein, low-carb guy.
"Nearly all the evolutionary theories of aging indicate there is a tradeoff between 'growth' and 'survival and aging,'" said David Le Couteur, one of the researchers. "An athlete needs to make a decision about what is important to him or her—it doesn't seem like you can have both."
According to Le Couteur, the issue lies in the level of branch chain amino acids (BCAAs) in the blood. "We were able to establish several mechanisms that we think linked the balance of micronutrients to lifespan," Le Couteur says. "High protein intake led to high circulating levels of branched chain amino acids, which was linked with activation of mTOR, changes in mitochondrial function and impaired insulin sensitivity These three cellular processes are linked with aging [more rapidly]."
Basically, the more protein you eat, the more BCAAs you consume, and the more BCAAs you consume, the more active are those three processes—activation of mTOR, changes in mitochondrial function and impaired insulin sensitivity. The more active those processes are, the faster your body ages. So although a high-protein diet might give you a leaner, healthier look on the outside, it's a different story on the inside. At the other extreme, high carbs and low protein reduce the amount of BCAAs in your blood, but also lead to a decrease in lean muscle and an increase in body fat. You might live longer, but you might look chubby.
The research also raises questions regarding supplementation with BCAAs, which many athletes do by taking them in powder form. "[Athletes] take branched chain amino acid supplements to build up their muscles, but our results would indicate this is bad for healthy aging," Le Couteur adds.
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