Proteins are macronutrients that people must consume in abundance to meet the body's need for tissue synthesis and repair. Protein makes up about 20 percent of the weight of the heart, skeletal muscles and liver, and 10 percent of brain tissue. The quality of protein you consume can significantly affect your health. With an increasing number of vegans and vegetarians, the quality of protein in vegetable versus animal sources is a prevalent topic.
Writing in the Journal of Physiology , the team behind the new mouse study report that lowering the consumption of specific types of amino acids called branched-chain amino acids (BCAAs) improved metabolic health, even when overall calories were not reduced.
"We've identified an unanticipated role for dietary BCAAs in the regulation of energy balance, and we show that a diet with low levels of BCAAs promotes leanness and good control of blood sugar," said Dr Dudley Lamming from the University of Wisconsin-Madison -- one of the lead investigators on the project.
The study found that feeding obese, pre-diabetic mice a specialised diet low in the amino acids leucine, isoleucine and valine promoted leanness and improved the regulation of blood sugar.
Importantly, mice in this study were free to eat as much of the low-BCAA food as they wanted, and so did not experience overall calorie reduction, noted the team.
Yet despite continuing to eat an unhealthy high-fat and high-sugar diet, mice on the low-BCAA diet still experienced an improvement in metabolic health.
"Our results also suggest that the specific amino acid composition of dietary protein - not just how much protein we eat - regulates metabolic health," said Lamming.
The team behind the mouse study said if these results can be translated to humans, it is possible that such diets, or drugs that mimic the effect of a low-BCAA diet, would be easier for people to follow and more effective than traditional calorie-counting diets.
They now hope low-BCAA dietary approach could be an effective way to treat or prevent metabolic syndrome, and will next investigate whether reducing dietary BCAAs can improve the metabolic health of humans, and how the specific amino acid composition of dietary protein regulates metabolic health.
"Our results link dietary BCAAs to the regulation of metabolic health and energy balance in obese animals, and suggest that specifically reducing dietary BCAAs may represent a highly translatable option for the treatment of obesity and insulin resistance" they concluded.