Amino acids have long been touted by the fitness and bodybuilding communities for their muscle building benefits. From ultra-bulk protein powders to lean mass-promoting snack bars, there’s no shortage of products available for those seeking a muscle boost.
However, protein’s popularity has also meant that less attention has been paid to researching its potentially negative side-effects.
Published today in Nature Metabolism, new research led by academics from the University of Sydney’s Charles Perkins Centre, Professor Stephen Simpson and Dr Samantha Solon-Biet, suggests that while delivering muscle-building benefits, excessive consumption of branched-chain amino acids (BCAAs) may reduce lifespan, negatively impact mood and lead to weight gain.
Dr Solon-Biet's research has investigated the complex role nutrition plays in mediating various aspects of metabolic health, reproduction, appetite and ageing.
“While diets high in protein and low in carbohydrates were shown to be beneficial for reproductive function, they had detrimental effects for health in mid-late life, and also led to a shortened lifespan,” she explained.
“What this new research has shown is that amino acid balance is important – it’s best to vary sources of protein to ensure you’re getting the best amino acid balance."
Using instruments at the University’s core research facility, Sydney Imaging, the research examined the impacts that dietary BCAAs and other essential amino acids such as tryptophan had on the health and body composition of mice.
“Supplementation of BCAAs resulted in high levels of BCAAs in the blood which competed with tryptophan for transport into the brain,” explained Academic Director of the Charles Perkins Centre's and researcher from the School of Life and Environmental Sciences Professor Stephen Simpson.
“Tryptophan is the sole precursor for the hormone serotonin, which is often called the ‘happiness chemical’ for its mood-enhancing effects and its role in promoting sleep. But serotonin does more than this, and therein lay the problem," he said.
“This then lowered serotonin levels in the brain, which in turn was a potent signal to increase appetite. The serotonin decrease caused by excess BCAA intake led to massive overeating in our mice, which became hugely obese and lived shorter lives.”
Mice were fed double the normal amount of BCAAs (200%), the standard amount (100%), half (50%) or one fifth (20%) for life. Mice who were fed 200% BCAAs increased their food intake, resulting in obesity and a shortened lifespan.
Qualified dietitian and public health nutritionist from the University of Sydney's School of Life and Environmental Sciences Dr Rosilene Ribeiro recommends eating a wide-range of proteins.
BCAAs are a group of three essential amino acids: leucine, isoleucine and valine, and are most commonly found in red meat and dairy. Whey protein - the most popular form of fitness protein - is made from dairy by-products and contains high levels of BCAA.