Some protein powders and shakes tested by Consumer Reports contained levels of lead, a heavy metal, that experts say could raise the risk of long-term health problems.

Scientists hired by Consumer Reports, an independent non-profit based out of the U.S., tested 23 popular protein products, and found lead levels ranging from zero to 7.7 micrograms per serving — above the stringent limits set by the state of California, but below U.S. Food and Drug Administration (FDA) standard for females of childbearing age.

There is no safe level of lead for human consumption, though it finds its way into many foods because lead is present in the environment.