While it may seem nuts, eat your cashews! One of the most intriguing areas of research in the field of probiotics and cancer has been the role that anacardic acid plays in activating immune cells. Anacardic acid is an active component found in cashew nut shell extract and the cashew apples. As far back as 1993, while testing the anti-tumor activity of prostaglandin synthetase inhibitors, Kubo, et al.6 found that the juice from the cashew tree apple had significant anti-tumoral properties against BT-20 breast carcinoma cells. Cashew apples are commonly found in Brazil, but rarely available in the United States. The active ingredient in this juice that intrigued the researchers is anacardic acid, which is also found in cashew nut oil, and to a lesser degree, in cashews themselves.
Kubo, et al.’s findings have been supported as recently as 2016, when Hollands, et al.7 were researching multi-drug resistant bacterial strains to address antibiotic resistance. In the process, they found that anacardic acid stimulates the production of reactive oxygen species and neutrophil extracellular traps, which in turn kills harmful bacteria and triggers cell death pathways, boosting innate immune defense.
In a study of the role immune checkpoint inhibitors play in melanoma Frankel, et al.8 found that positive response to immune checkpoint inhibitors were associated with the presence of specific gut bacteria which induced the maturation of T cells and dendritic cells. In the process of conducting the study, however, they were surprised to discover that those who responded best had high levels of anacardic acid. The researchers concluded that anacardic acid activates immune cells.