Q: Yesterday, I heard a radio announcer say that the guyabano fruit is a natural cancer cell killer that is 10,000 times stronger than chemotherapy. Is there any truth to this? --firstname.lastname@example.org
A: That the guyabano has anti-cancer properties is one gross misinformation that has been circulating in the Internet for years now. More than two years ago, I was sent an email by a cancer-survivor friend of mine who attributes her survival from breast cancer to her regular intake of guyabano juice. About eight years earlier, she was diagnosed with stage I cancer of the breast for which she underwent surgery and chemotherapy. She started drinking guyabano juice after her chemotherapy and has since credited the fruit, rather than her doctors, for her apparent cure.
When I received her email, out of curiosity, I did a library and Internet search for guyabano. I was amazed with what I found out and wrote an article, which was later published in this column, about the alleged "miraculous properties" of guyabano. Nothing much has changed regarding this issue since, so most of what I am going to write herewith I have told readers before.
Guyabano is the Filipino term for the graviola tree (Annona reticulate). Its delectable fruitis also locally referred to as guyabano but is known as custard apple or sour sop in English.
Folklore attributes some medicinal properties to guyabano. Supposedly, its unripe fruit can relieve diarrhea, its leaves can eliminate worms when taken internally and heal wounds when applied topically, and a concoction of its roots can reduce fever.
Traditional medicine does not ascribe anti-cancer properties to guyabano but there are numerous web sites that promote graviola as an anti-cancer remedy. Of course, most of these web sites also promote the graviola supplements made from roots, stems and fruits of the tree that they sell. There are web sites that claim that guyabano is 10,000 times stronger than the Adriamycin, a drug which is used in the chemotherapy for breast and other forms of cancer. But, the numerous evidence that these websites present to support their claim are mostly anecdotal and pseudoscientific in nature. Simply put, there is no scientific evidence that proves that guyabano has anti-cancer properties.
The idea that graviola is an effective cancer fighter evidently stems from research (published in 2008) conducted at the Purdue University's School of Pharmacy and Pharmaceutical Sciences on the unique substances known as annonaceousacetogenins that have been extracted from the graviola tree. The Purdue investigators found these substances to be potent inhibitors of cancer cells while leaving normal cells alone. They also found the compounds to be effective against drug-resistant cancer cells.
But these studies were conducted in vitro, i.e., conducted on cancer cells in test tubes. These are a long way from clinical trials that determine the efficacy and safety of these compounds in people with cancer. In fact, I have not found any human study on graviola and cancer.
As to the suggestion, by some of the websites, that scientific evidence in favor of graviola is being suppressed by drug corporations, I find this inconceivable. I'm more inclined to believe that this conspiracy theory has been concocted by those who sell graviola supplements. In fact, if these business entities that manufacture and sell supplements want to, they can easily undertake scientifically acceptable research on guyabano and publish their findings. But they don't. Instead, they label their products as having "no therapeutic claims" while at the same time they try to make the public believe that they are actually effective and even better than proprietary medicines.
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