Protein has been a real trend in recent times, one of the only nutrients that receives plenty of good press and barely, if any, negative coverage.
However, an Australian study has claimed that consuming protein in the form of a shake can affect your mortality.
Australian GP Dr Sam Hay explains: "This study found that protein shakes with added amino acids could cause premature death, mood swings and obesity."
Dr Hay told bodyandsoul.com.au that because the study wasn't conducted on humans, the results will differ, but it's indicative of some things we should be wary of.
He highlights: "Firstly, there's a huge variation in what constitutes a 'protein shake'.
"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."
Dr Hay says he's not suggesting you never consume protein powder again.
However, he emphasises it should only be used as a substitute - when you can't consume proteins in food.
He recommended to bodyandsoul.com.au that no more than 1.5g/kg of protein powder should be used daily.
"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."