Texans General Manager Rick Smith said he was "disappointed" in the suspension of the starting lineman, which is to take effect immediately.
"This is a significant blow to our team," he said. "Our players have to understand that they are responsible for what goes into their bodies and that they take risks anytime they use a supplement not approved by the NFL."
Brown issued an apology Tuesday to his teammates, family and Texans fans.
"I take full responsibility for putting myself in this situation," he said. "I unknowingly took a supplement tainted with a banned substance and now have to deal with the consequences."
Brown will be eligible for reinstatement Oct. 18.
LGBT community has 'bullied the American people': Bachmann
Beautician charged with giving client fatal silicone butt injection