The leaves of the papaya tree may be a new weapon against cancer.   Researchers are trying to nail down which components of the plant can kill tumors.  

The papaya (Carica papaya) is a tropical fruit that looks like a melon. A one-half cup serving of papaya contains only 25 calories and no fat, cholesterol or sodium. Papaya is also a good source of vitamin C and provides a small amount of vitamin A.

Nam Dang, M.D., Ph.D. Researcher with the University of Florida in Gainesville, says in his native Vietnam, some people use papaya as a form of alternative medicine. Anecdotal reports suggest a tea made from the papaya plant may help keep some types of cancer in remission.

According to Dang, the tea is made by drying the leaves in the sun until they turn brown. One leaf is then placed in a pot with boiling water and allowed to steep. The “tea” is consumed over the next two to three days. Then a new batch of tea is made. In the stories he has heard, cancer patients have used the tea for months to years to keep the disease in check and have not experienced any side effects from the homemade brew.

Without any scientific evidence, there is no way to substantiate the claims made by those who drink papaya tea. So Dang and his colleagues decided to investigate the effects of a papaya leaf extract in a laboratory. The leaf extract was used on cancer cell lines, including cancers of the breast, cervix, liver, lung and pancreas.

When the cancer cell lines were incubated with the papaya leaf extract, investigators saw a two-pronged effect. First, many of the cancer cells died. Second, the extract also boosted the immune cells, improving the ability of those cells to secrete chemicals that help the body fight cancer. Another advantage is that the papaya leaf extract had no toxic effects on normal cells.

Currently, Dang is trying to determine what components of the papaya leaf extract serve as cancer fighters. He believes a key source component may be papain, an enzyme found in the fruit and leaves of the papaya. If the beneficial ingredient can be found, it can be synthetically created in a lab. Then investigators could determine what kind of dosage is needed to fight cancer and, potentially, other immune-related diseases.

Eventually, a drug made from the papaya leaf may be used in addition with traditional therapies to boost the effectiveness of cancer treatments. Dang hopes to conduct human clinical trials of papaya tea in the next few years.