Well no they're not good for you. Good for you would be to eat a healthy diet, exercise regularly, eat less calories than you burn and don't take any pills.
Just because a product is labeled 'natural' or from an herbal source it is not guaranteed to be safe. Either the herb has no effect, in which case why bother, or it has an effect, in which case it's a drug.
Ephedrine, also known as ephedra or ma huang, has sickened or killed 800 users.
Ephedra, derived from an Asiatic shrub, contains ephedrine, a stimulant that acts on the central nervous system. It is found in products, such as Metabolife, metabolite, advocare and other products. The FDA believes that ephedra may be related to more than 50 deaths. Most of the serious injuries involve high blood pressure that can cause bleeding in the brain, a stroke or a heart attack.