Gym-goers can sometimes be seen clutching protein shakes as if in possession of a magic muscle-building elixir or a tin of Popeye’s spinach, gulping down mouthfuls between sets and furtive mirror glances.

But there is a 50-50 chance the powders used to make the shakes contain amounts of toxic metals deemed unsafe in some quarters.

That’s according to the Clean Label Project, whose mission, its executive director Jaclyn “Jackie” Bowen says, is “to uncover the hidden risks of environmental contaminants and toxins lurking in everyday products”.

The United States-based non-profit organisation said that it tested 160 products produced by 70 brands – equivalent to 83% of the US protein powder market – and found that 47% contained levels of metal exceeding the threshold in Prop 65, a California state law known officially as the Safe Drinking Water and Toxic Enforcement Act of 1986.

Plant-based proteins were found to have higher levels of metals in them than whey powders, while chocolate-flavoured powders had four times as much lead as vanilla powders, and organic mixes had three times the amount of cadmium as whey powders.

If they don’t lead to people eating more chicken, eggs, fish and meat to get their protein, they should at least serve as “a wake-up call for consumers, manufacturers, retailers and regulators”, the Clean Label Project said, adding that there needs to be “stricter safety standards to protect consumers from long-term exposure to these contaminants”.

“Consumers are purchasing supplement and protein products for health and performance; they expect the products to be clean,” Bowen noted. – dpa