An Australian study has made the surprising claim that protein shakes can affect your mortality.

We asked our resident GP, Dr Sam Hay, to weigh in. “This study found that protein shakes with added amino acids could cause premature death, mood swings and obesity,” he explains.

He notes that the study wasn’t done on humans, so the outcomes won’t necessarily be the same, but says we can learn some lessons from this.

“Firstly, there’s a huge variation in what constitutes a ‘protein shake’,” he says. “Simple casein or whey protein powders should be 100 per cent natural, but products with added branched-chain amino acids [BCAAs] are the ones you need to watch out for. Small amounts here and there are unlikely to be an issue, but this report does highlight increasing evidence that they may well be.”

While he says this doesn’t mean you need to stop using protein powders altogether, he adds it’s important to remember they’re just for convenience and you shouldn’t consume more than 1.5g/kg per day.

“Consider these results as a warning that unnatural sources of BCAAs are perhaps not as safe as we first thought. It’s changed my opinion and I won’t be using them again.”