Nothing on this page sounds like a resounding endorsement:
> An athlete should never consider any dietary supplement to be 100% safe. No third-party testing company can test for every possible prohibited substance. The NSF Certified for Sport program reduces, but does not eliminate, risk for athletes. It is still up to each athlete to determine whether they want to take the risk of using dietary supplements and USADA does not approve or evaluate dietary supplement products.
It also seems focused on illegal substances, not the purity of the product.
> An athlete should never consider any dietary supplement to be 100% safe. No third-party testing company can test for every possible prohibited substance. The NSF Certified for Sport program reduces, but does not eliminate, risk for athletes. It is still up to each athlete to determine whether they want to take the risk of using dietary supplements and USADA does not approve or evaluate dietary supplement products.
It also seems focused on illegal substances, not the purity of the product.