Guyabano for cancer?

A balikbayan patient asked me recently about the anticancer effects of custard apple or sour sop. I was embarrassed to admit I didn’t quite know what the fruit was, but promised her I would request my research staff to search the scientific literatures about it.

I gave the assignment to my senior researcher and editor Gigi de Leon, and she came back to me a few hours later educating me on what the custard apple or sour sop is. It is our good old guyabano, which I fondly remember I loved eating when I was a child. During summer when we vacationed in our hometown, we would climb our neighbor’s wooden fence and help ourselves to the several guyabano trees they have in their backyard. I can still taste the luscious, sweet  pulp of our neighbor’s guyabano.

Many years later when that neighbor came to see me in the clinic, I would joke that I can’t charge him for professional fees because I have to pay back for all the guyabano fruits my friends and I have stolen from their backyard when we were children.

Marketed as a cure-all

It came as a pleasant surprise to hear that the fruit has some anticancer potential. But that’s how it stands for now. There is some suggestion that it might have the property to inhibit the growth of some cancer cells, but this has only been shown in the laboratory—or at most, in experimental animals—but never in humans. It’s a long way from being declared an anticancer fruit with truly clinically meaningful effects.

I hear that it’s now being unscrupulously  marketed by several networking companies as a cure-all. The fruit, together with its leaves, stem, roots, seeds and bark, is concocted into expensive juices and capsules, and is marketed to cure asthma, arthritis, heart and liver diseases. It also reportedly lowers blood pressure, strengthens the immune system, improves energy levels, heals wounds, eliminates worms, relieves diarrhea and fever, treats gonorrhea and herpes. But its biggest draw is that it is supposed to be “a miraculous natural cancer cell killer 10,000 times stronger than chemotherapy.”

When you have strong and obviously exaggerated claims like this, you tend to doubt and we should ask for published scientific evidence.

One literature Gigi came across with even claims guyabano extracts are 10,000 times stronger than adriamycin, a drug used in chemotherapy treatments. No published clinical trials on human is available. Some websites just provide testimonials from individuals relating anecdotes about their cancer sickness, how they opted not to follow their doctor’s recommendation to undergo surgery or chemotherapy and just take guyabano products.

They believe that the fruit cured them from their cancer, which was already late-stage or Stage 4 in some cases. Whether they really had cancer or not, we’re not sure, because no documentation of their cancer is presented.

In fairness to the ones marketing these medicinal guyabano extracts, there’s a modicum of basis for their claims, but what is unacceptable is their exaggeration of the fruit’s health benefits as if it’s already tried and tested.

Researches

According to the scientific literatures gathered by Gigi, researches have been undertaken to uncover guyabano’s anticancer effects, starting in 1976 when the National Cancer Institute in the United States conducted the first study on the fruit’s supposed cancer fighting properties.

This was followed by 20 more laboratory tests conducted in various laboratories worldwide. They all came out with unanimous results: Guyabano tree extracts, indeed, proved to be effective against the growth of malignant cells in 12 cancer types. These include some of the deadliest cancer forms which have taken the lives of many around the globe: pancreatic, colon, lung, prostate and breast cancers.

According to the Catholic University of South Korea and Purdue University in Indiana, United States, guyabano tree extracts acted in a way that prevented it from harming normal cells, while successfully targeting the dangerous ones, unlike chemotherapy, which destroys all cells that multiply. The findings of the Catholic University of South Korea were published in the Journal of Natural Products.

But, it has to be emphasized that all of these trials were conducted in the laboratory only using nonliving models, or what is called as in vitro experiments. Absolutely, no research in humans, so far.

So, my advice is—rather than buying all these expensive commercialized extracts, juices and capsules of guyabano, I think it’s a lot more enjoyable and economical to just buy the fruit, and savor its delicious, citrusy white flesh. Personally, I would do that. Just like in my childhood.