Well, sort of.

From the article:
Fehr told the players that they can call a Major League Baseball hotline if they have questions about a supplement, or they can send the product to the league for testing.
...
"We have this tiny list of approved substances that includes things like Gatorade," Lidge said. "Guys are like, 'Can I take some protein? Can I eat a protein bar?' You send it to get checked, and it takes two months to get back. It's a difficult time. Everyone is so scared - players and the union - of doing anything wrong."

h/t to BBTF