Recreational marijuana sales start Jan. 1. Here's how weed does, and doesn't affect your health The FDA cried fraud in October, accusing companies in Florida, Colorado and California of illegally selling marijuana-derived products that supposedly could prevent, treat or cure cancer.The advertising claims were unsubstantiated, said the FDA, and the products hadn’t been submitted for approval.It was a public shaming that also served as a timely buyer-beware message for California, where the sale of marijuana will be expanded from medical purposes to recreational use in January.