Over-reliance on protein shakes in your diet could shorten your lifespan and negatively affect your mood, according to new research.
Protein powder shakes have long been loved by fitness fanatics and bodybuilders, and more and more people are turning to them to help them get the toned physique they want.
However, scientists at the University of Sydney's Charles Perkins Centre have produced an important new study showing that relying on protein shakes could have adverse consequences for your health in later life.
They found that mice who consumed double the normal amount of branched-chain amino acids (BCAAs) provided by shakes tended to overeat and gain weight, resulting in obesity and a shortened lifespan.
Study co-author Dr Samantha Solon-Biet, said that it is important to maintain a balance of the amino acids in your body.
"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."
Her colleague Professor Stephen Simpson said that the problem was likely caused by ingesting BCAAs rather than tryptophan, an amino acid that plays an important role in helping the body produce the mood-enhancing chemical serotonin.
"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 warned. "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."
The researchers suggest only using protein shakes sparingly and getting most of your protein from natural sources such as red meat, dairy, chicken, fish and eggs, or if you're vegetarian or vegan, beans, lentils, nuts and soy proteins. Seeds and nuts in particular are importan sources of tryptophan, meaning they may help stabilise or improve your moods.