Little clinical evidence supports the use of papaya seeds to treat intestinal parasites - Health Feedback
Inadequate support: Although several studies have found evidence that papaya seed extract interferes with the development of yeast, there isn't clinical evidence of the effectiveness of papaya seeds for treating yeast infections.
FULL CLAIM: "Papaya and papaya seeds contain compounds that naturally kill parasites, including the same parasites that are actually known to cause yeast infections"
REVIEW
Papaya is the fruit of the Carica papaya tree. It is one of the most consumed fruits worldwide and is rich in nutrients. Papaya also contains an enzyme called papain, which has important industrial and biotechnological uses. Ripe papayas contain numerous black round seeds, which are edible.
In late September, several videos went viral on social media platforms claiming that papaya seeds have beneficial health effects, including killing intestinal parasites. This viral trend emerged in 2021, as can be seen in this article from the Miami Herald and this one from the Cleveland Clinic, but new videos keep emerging with the same claim (like this one, this one and this one).
Such claims lack sufficient scientific evidence. As we will explain in this review, the evidence suggesting that papaya seeds eliminate intestinal parasites is limited to two small studies that focused only on a specific type of intestinal parasite called roundworm.
Gastrointestinal parasitic infections constitute a global health problem, mainly affecting tropical regions where water and sanitation facilities are inadequate. Intestinal parasitic infections are of particular concern in children, causing diarrhea, anemia and malnutrition. Intestinal parasitic infections can be caused by intestinal worms and protozoa[1].
Roundworms, also called nematodes, are a group of animals that can cause parasitic diseases in humans and other mammalian species, such as cats or dogs. Some roundworms are microscopic in size while others are visible to the naked eye. Ascaris lumbricoides, also known as "large roundworm", is the most common parasitic roundworm in humans and also the largest, reaching a length of 3.5 cm. Roundworms are only one of several types of intestinal parasitic worms, which also include tapeworms (cestodes), such as the pork tapeworm, or intestinal flukes (trematodes).
One of the few clinical studies to test the effect of papaya seeds on intestinal parasites was conducted on a group of 60 children in Nigeria[2]. This pilot study tested for the presence of microscopic intestinal parasites in stool samples and found a higher rate of stool clearance (samples not showing parasites) in those children who consumed 4 g of grounded dry papaya seeds with honey (77%), compared to a control group of children who consumed only honey (17%).
Among the group of children who consumed papaya seeds, 85% of them cleared A. lumbricoides from their stools within seven days and 100% eliminated Strongyloides stercoralis, two species of roundworms. The study also found a reduced presence of other parasitic organisms in the group consuming papaya, but this effect wasn't considered to be significantly different compared to the control group.
However, 17% of children in the control group that didn't eat papaya seed also exhibited stool clearance, a result that the authors of the study could not explain. Further large-scale studies in humans are needed to verify the results, as the small size of the treatment and control groups could produce a lot of variability, which could make it more difficult to observe an effect—if there is one—or conversely, create the semblance of an effect where there is actually none.
Another study that tested the antiparasitic effect of papaya seeds in children was conducted in Kenya[3]. This study lasted eight weeks and involved 326 children, who received either a plain corn flour porridge, or a fortified porridge containing the anti-worm medication albendazole, or a fortified porridge containing 10 g of grounded dry papaya seeds. Children who ate porridge fortified with papaya seeds had 64% fewer A. lumbricoides eggs in their stool samples after two months compared to those who ate plain porridge; on the other hand, those who ate porridge fortified with albendazole had 79% fewer eggs than the control group.
The effect that papaya seeds have on roundworms is mainly due to a substance known as benzyl isothiocyanate[4]. A study showed that benzyl isothiocyanate extracted from papaya seeds was able to kill the roundworm Caenorhabditis elegans, leading the authors to hypothesize that a moderate amount of papaya seeds could have the same effect on intestinal roundworms, based on the amount of benzyl isothiocyanate needed to kill C. elegans. However, this hasn't been tested yet.
Some concerns have been raised about the safety of papaya seeds, as they contain trace amounts of cyanide[5]. One study in mice found that papaya seed extract caused sterility in male rats, although this effect was reversible[6]. Therefore, before recommending any therapeutic use of papaya seeds, an evaluation of its safety is necessary.
Experts who weighed in on these viral videos don't recommend consuming papaya seeds for the treatment of parasitic infections. Gastroenterologist Nitin Ahuja told the Miami Herald that excessive consumption of these seeds can cause stomach problems. Furthermore, according to gastroenterologist Christine Lee, it is important to make an accurate diagnosis if the presence of intestinal parasites is suspected, to rule out other possible causes of the symptoms. About the available clinical trials with papaya seeds, Lee said:
"These are small studies and should not be extrapolated to general use without quality randomized, controlled, prospective trials with larger sample sizes. We need to know if papaya seeds really work and if they are safe for human use."
One video that claimed that papaya seeds have compounds that can kill parasites also claimed that these parasites are the cause of yeast infections, suggesting that papaya seeds may be useful for treating yeast infections. Yeast infections are caused by a type of single-cell fungi called yeasts. The most common of these infections is candidiasis, which is caused by several species of Candida, mainly C. albicans.
Several laboratory studies have reported that papaya seed extract inhibits Candida growth[7,8]. This effect was attributed to the benzyl isothiocyanate present in papaya seed extract. However, no clinical trials have shown that papaya seeds are effective at treating yeast infections in people.
In conclusion, clinical evidence of the effectiveness of papaya seeds in treating parasitic infections is limited to a few small studies that tested the effect of papaya seeds against roundworms. The effect of papaya seeds on other types of intestinal parasites hasn't been demonstrated. There is therefore insufficient evidence for the claim that papaya seeds can kill intestinal parasites in general. Larger randomized clinical trials are still needed to better understand the effect of papaya seeds against other parasites, as well as to test the safety of papaya seed compounds in people.
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