Does eating cashews kill bacteria? No, that's not true: Scientific research suggests that there isn't enough anacardic acid in the cashew itself to kill bacteria or provide any therapeutic value. But, discarded cashew shells could possibly have antibacterial and immune-boosting properties, if reduced and purified to drug form.
The claim appeared as a meme in a Facebook post on November 17, 2021, from Ultimate Health Goals. It says:
DID YOU KNOW? Bacteria, which cause tooth decay, acne, tuberculosis, Streptococcus pneumoniae, are all killed eating cashew nuts which are actually seeds.
This is what the post looked like on Facebook at the time of writing:
(Source: Facebook screenshot taken on Wed Dec 1 19:27:27 2021 UTC)
The University of California at San Diego emailed us on November 30, 2021, with information from Dr. Vincent Nizet, a distinguished professor at the Health Sciences Department: "Anacardic acid is a blanket term applied to a family of closely related compounds consisting of salicylic acid with a 15-carbon alkyl chain, which exist either in a fully saturated form or as a monoene, diene, or triene."
While anacardic acid has been shown to "exhibit direct antimicrobial activity against a number of bacterial species," Nizet wrote, "there is probably not a high enough of a concentration in cashews to have any of the clear medicinal benefits."
While cashew shells are not really edible and can be toxic, "Anacardic acid, which is present in the (discarded) cashew nut shell oil can be purified as a natural drug product from the shells, and has several antibacterial and immune-boosting properties," Nizet wrote.
Dr. Mallory Abate, an assistant professor of dermatology at the Saint Louis University School of Medicine, told Lead Stories in a November 30, 2021, email that eating cashews to prevent acne "is a myth."
"There are different types of acne, but the root cause of all acne starts with sebum overproduction which leads to follicular occlusion," she wrote. "In some types of inflammatory acne, there is a subsequent overgrowth of bacteria - P. acnes - that can lead to inflammatory lesions, but again this is not the root cause of the acne. Thus, eating something like cashews, could not prevent acne from forming."