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Does your protein shake come with unwanted side effects?

In a recent study, researchers investigated the long-term health effects of dietary amino acid supplements, such as protein shakes.

Protein shakes, powders, and snack supplements containing amino acids are popular amongst fitness and bodybuilding enthusiasts for their muscle building benefits. Branch-chain amino acids (BCAAs) are a group of three essential amino acids: leucine, isoleucine, and valine, mostly found in red meat and dairy products. Whey protein, a popular form of fitness protein, is made from dairy products and contains high levels of BCAAs.

Long term effects of dietary branch-chain amino acids on health unknown

Whilst BCAAs can increase lean body mass, they are associated with obesity and insulin resistance. Little is known about how long-term dietary BCAAs affect health and lifespan. In laboratory investigations, researchers at the University of Sydney, Australia, looked at the effects of long-term dietary BCAAs in mice. They recently reported their findings in Nature Metabolism.

The researchers fed groups of mice different amounts of BCAAs in their diet: twice standard (200%), standard (100%), half-standard (50%), and one-fifth (20%). They compared the effects of different amounts of BCAAs on metabolism, appetite, obesity, and lifespan.

High BCAA diets in mice led to overeating and obesity

The researchers found that mice fed high levels of BCAAs (twice standard, 200%) had lowered levels of serotonin in the brain, a potent signal to increase appetite. These mice displayed massive overeating, leading to obesity and a shortened life-span.

Balanced and varied protein diets are important for health

“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,” said Dr. Solon-Biet, the lead author of the paper. The researchers recommend eating a healthy balanced diet that includes a variety of protein sources, plus other essentials such as fiber, vitamins, and minerals.

Written by Julie McShane, Medical Writer


  1. Solon-Biet SM, Cogger VC, Simpson SJ, et al. Branched-chain amino acids impact health and lifespan indirectly via amino acid balance and appetite control. Nature Metabolism, 29 April 2019. Doi: 10.1038/s42255-019-0059-2.
  2. University of Sydney. Press release 30 April 2019. “Put down the protein shake: Variety of protein better for health”
Julie Mcshane MA MB BS
Julie Mcshane MA MB BS
Julie studied medicine at the Universities of Cambridge and London, UK. Whilst in medical practice, she developed an interest in medical writing and moved to a career in medical communications. She worked with companies in London and Hong Kong on a wide variety of medical education projects. Originally from Ireland, Julie is now based in Dublin, where she is a freelance medical writer. She enjoys contributing to the Medical News Bulletin to help provide a source of accurate and clear information about the latest developments in medical research.


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