An ancient herb called Ashwagandha (Latin name Withania Somnifera) shows great promise in the treatment and prevention of cancer. Research has shown that the herb is toxic to several types of cancer cells, increases the effects radiation therapy to treat cancer while decreasing side-effects, and reduces side-effects from chemotherapy.
The author of a review on the herbs-anti-cancer effects summarizes that "it can be concluded that Withania somnifera reduces tumor cell proliferation while increasing overall animal survival time. Furthermore, it has been shown to enhance the effectiveness of radiation therapy while potentially mitigating undesirable side effects. Withania somnifera also reduces the side effects of chemotherapeutic agents cyclophosphamide and paclitaxel without interfering with the tumor-reducing actions of the drugs."
This herb can also be used to increase energy levels and improve sleep.