It has long been known that eating potatoes is good for bowel health, but new research suggests that they may also have a beneficial effect on the whole immune system. Especially if eaten cold or in a potato salad, Anne Pichon reports in Chemistry & Industry, the magazine of the SCI.

The general down-regulation of leucocytes observed by the Spanish researchers suggests an overall beneficial effect, a generally more healthy body, according to immunology expert Lena Ohman at the Department of Internal Medicine, Göteborg University, Sweden. A reduction in leucocyte levels of about 15% was observed in the RPS pigs. Lower lymphocyte levels are also indicative of reduced levels of inflammation, but according to Ohman, the observed reduction in both lymphocyte density and lymphocyte apoptosis by the Spanish researchers is surprising

Starch consumption is thought to reduce the risk of large bowel cancer and may also have an effect on irritable bowel syndrome (IBS). Ohman’s team previously found that the overall lymphocyte levels do not vary for IBS patients, but that lymphocytes are transferred from the peripheral blood to the gut, which support the hypothesis of IBS being at least partially an inflammatory disorder. She says the decrease in lymphocytes observed by the Spanish is therefore interesting, and a diet of resistant starch may be worth trying in IBS patients.

Humans do not eat raw potatoes, but they do eat a lot of foods that contain resistant starch, such as cold boiled potatoes, legumes, grains, green bananas, pasta and cereals About 10% of the starch eaten by human is resistant starch – starch that is not digested in the small intestine and so is shunted into the large intestine where it ferments.