Certain germanium compounds have a low mammalian toxicity, but a clear activity against certain bacteria, which makes them of interest as chemotherapeutic agents.

Proponents claim germanium can be used to treat leukemia and cancers of the lung, bladder, larynx, breast, and uterus. They also claim it can help neurosis, asthma, diabetes, hypertension, cardiac insufficiency, Parkinson’s disease, neuralgia, chronic fatigue, hepatitis, and cirrhosis of the liver. Supporters say germanium stimulates the body's production of interferon, a naturally occurring anti-cancer agent. Some say that it helps the immune system by boosting the activity of natural killer cells, a type of white blood cell that attacks invading germs.

The late Dr. Kazuhiko Asai of Japan began investigating the biological properties of germanium after reading reports from Russia that said the mineral had tremendous therapeutic value. In 1969, Dr. Asai founded the Asai Germanium Research Institute. He reported that he had developed a way to produce germanium that was chemically identical to the germanium extracted from plants. Dr. Asai also found that germanium was present in many common herbal remedies, including ginseng, garlic, comfrey, and aloe.

Dr. Otto Warburg, a Nobel Prize winning biochemist, stated that germanium helped to increase the delivery of oxygen to cells. He believed that boosting the oxygen supply to healthy cells slowed the growth of tumors.