Potential bad news for those who go nuts for peanuts: According to a recent study, it seems the beloved snack could be linked to an increased risk of cancer spread. The study, published in the journal Carcinogenesis, found that in cancer patients, a protein present in peanuts – Peanut agglutinin (PNA) – can enhance the secretion of two molecules known to promote the spread of cancer. These molecules are cytokines, small proteins important in cell signaling and the body’s immune response. IL-6 and MCP-1, as they are commonly but not very catchily known, promote cancer metastasis and enhance the expression of adhesion molecules on the surface of endothelial cells, which line blood vessel walls. These adorned endothelial cells become more attractive to circulating tumor cells, thus increasing the number of interactions between the two – leading to a greater risk of metastasis. “Although further research and investigation are still needed, these studies suggest that very frequent consumption of peanuts by cancer patients might increase the risk of metastatic spread,” corresponding author Professor Lu-Gang Yu of the University of Liverpool said in a statement. PNA is a carbohydrate-binding protein that rapidly enters the bloodstream after peanuts are eaten as it is resistant to cooking and digestion. It accounts for only about 0.15 percent of peanut weight. While the present study details induction of cytokines by PNA interacting with endothelial cells, a previous study by the same authors found an alternative route by which it might promote tumor spread. PNA interacts with a protein expressed on the surface of tumor cells in the bloodstream, triggering changes in the protein that make the cancer cells stickier and more likely to attach to blood vessels. This stickiness also allows the cancer cells to clump together, prolonging their survival as they circulate. Before you renounce peanuts altogether and embark on your new peanut-free life, it should be pointed out that in previous studies substantial blood PNA concentrations were only seen after an exceptionally large amount of peanuts were consumed – 250 grams (9 ounces). The recommended daily serving is 28 grams (1 ounce), or about 28 peanuts. “It may be that ‘normal’ peanut consumption yielding lower PNA concentrations is harmless,” Yu said. It is also worth noting that there has been no link made to cancer mortality – in fact, one large US study reported “no significant impact of peanut consumption on cancer mortality”, while in another “peanut consumption was reported to have no significant effect on prognosis in men with established prostate cancer,” according to Yu. Much more research is needed for us to understand the impact of eating peanuts on the spread of tumors in cancer patients. “Nevertheless, the possibility remains that circulating PNA, at least at the relatively high levels found shortly after a large “dose” of peanuts, could have a significant biological effect on tumour cells [...] with a potential for increased risk of metastasis,” said Yu. “Heavy or very frequent peanut consumption therefore might be better avoided by cancer patients.” Someone should probably let these acrobat squirrels know too – the little guys appear to have missed the memo. Source
