Conventional medicine, also called allopathic medicine, is based on scientific knowledge of the body and uses treatments that are based on scientific research. It is practiced by healthcare practitioners who hold an M.D. (doctor of medicine) or D.O. (doctor of osteopathy). Conventional medicine is also referred to as Western medicine. Complementary and alternative medicine are healthcare systems, practices and products that are generally not considered to be in the mainstream of conventional medicine. There may be some scientific evidence for some CAM therapies, but for most CAM therapies there are still questions that have not been answered through well-designed scientific studies. CAM therapies are often based on the belief that a healthcare provider must treat the whole person—body, mind, and spirit—as a unit. Most CAM therapies are less invasive than conventional medicine.