As a reminder, we do not recommend adding any packaged protein powders to your smoothies. Eating whole foods and drinking green smoothies can provide you with plenty of quality protein.

The report tested popular protein powders and tested for arsenic, cadmium, lead and mercury.  The study  found that many products contained significant amounts of heavy metals and that consuming the recommended daily servings exceeded any proposed limits on consuming such toxins.

But federal regulations do not generally require that protein drinks and other dietary supplements be tested before they are sold to ensure that they are safe, effective, and free of contaminants, as the rules require of prescription drugs.
“Most consumers and even many doctors don’t realize that in this country we’re left to simply trust the manufacturer to decide what level of quality and safety they’ll provide,” says Pieter Cohen, an internist at Cambridge Health Alliance and author of a recent New England Journal of Medicine article on contaminants in dietary supplements. Even in California, some manufacturers don’t comply with the requirements of Proposition 65 to put warnings on supplements, and enforcement seems to be lax. Sometimes warnings appear only after lawsuits are filed.

See the complete report here