Protein shakes and bars are great for building muscle but regular use could lead to mid-life health problems an even a shortened life-span.
That’s the conclusion of a team of researchers at the University of Sydney
Who recently examined whether there are any ongoing ramifications or potential side-effects from long-term high protein intake or from consuming certain types of amino acids.
The Australian team say that protein’s popularity in recent years – which has supported a fast-growing market for shakes, bard and supplement products – has meant that less attention has been paid to researching its potentially negative side-effects.
Published this month 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.”
BCAAs could influence mood – and lead to overeating
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.
Increase protein variety for health benefits
Dr Rosilene Ribeiro, a nutrition specialist at the University of Sydney’s School of Life and Environmental Sciences says that people should increase protein variety to avoid potential harm from long-term use of protein products. She recommends:
- It’s important to vary protein sources in order to get a variety of essential amino acids, through a healthy and balanced diet rich in fibre, vitamins and minerals.
- BCAAs are essential amino acids present in protein-containing foods, with red meat and dairy being the richest sources. Chicken, fish and eggs are also nutritious sources of BCAAs.
- Vegetarians can find BCAAs in beans, lentils, nuts and soy proteins.
- Foods rich in tryptophan include seeds and nuts, soy beans, cheese, chicken, turkey and interestingly, crocodile.
Study findings branded ‘questionable’ by US trade group
The Australian study, which garnered headlines around the world, has been criticised by US trade group the Natural Products Association. In a letter to the editor of the UK-based Daily Mail newspaper, which gave high-visibility coverage to the study’s findings, the NPA’s CEO Dan Fabricant, called the research a “questionable study on mice to make claims that should have sports doctors, nutritionists, and athletes at all levels of competition scratching their heads”.
He went on: “The authors offered no empirical research from humans, relying entirely on lab mice to draw conclusions that could never be replicated in the human diet. The researchers could have conducted diet surveys on humans to ask whether eating BCAA diets led consumers to eat more and eat more unhealthy foods, but they didn’t.”