Marijuana doesn’t cure cancer. It has not been shown to somehow explode tumor cells or promote the growth of new brain cells, the Food and Drug Administration said Wednesday. The FDA warned four companies to stop making these unproven claims and to stop selling cannabis-based hemp and marijuana products that claim to treat cancer or any other medical condition. “Substances that contain components of marijuana will be treated like any other products that make unproven claims to shrink cancer tumors,” FDA Commissioner Dr. Scott Gottlieb said in a statement. The FDA says it is not trying to shut down the sales -- just to stop sellers from making unproven medical claims. “We don’t let companies market products that deliberately prey on sick people with baseless claims that their substance can shrink or cure cancer and we’re not going to look the other way on enforcing these principles when it comes to marijuana-containing products.” Medical marijuana is legal in 29 states, as well as in Guam and Puerto Rico. Studies have shown that it can have some benefits in reducing anxiety, counteracting some types of nausea, and that it may relieve some symptoms of glaucoma and multiple sclerosis. A cannabis derivative called cannabidiol or CBD for short has been shown to help kids with a severe form of epilepsy called Dravet syndrome and perhaps it can help treat Parkinson’s disease. The federal government still regulates marijuana as a controlled substance, but the Obama administration had a policy deferring to the states to regulate it. With loosening enforcement of laws, sites and clinics have escalated offers of various marijuana and hemp-based treatments, including many selling CBD oils or creams. “When people are allowed to illegally market agents that deliver no established benefit they may steer patients away from products that have proven, anti-tumor effects that could extend lives.” The FDA warning comes down on four of them: CW (Charlotte’s Web) Botanicals; Natural Alchemist; Greenroads Health; and That’s Natural Marketing and Consulting. They all have made unproven claims that their products treat cancer, the FDA said. Not only are the claims not proven, but they