They've tested it against low-fibre wheat bread and reckon it reduces the risk of type 2 diabetes. It does this by controlling levels of intestinal serotonin which, in turn, keeps blood sugar (glucose) levels in check.
Serotonin is best known as a neurotransmitter that helps control brain signalling, but the variety created in the gut has an impact on glucose. Too much intestinal serotonin can cause high levels of blood sugar—and that, in turn, can lead to diabetes.
That's why wholegrain bread is known to reduce the risk of diabetes, say researchers at the University of Eastern Finland, and may also lower the risk of colorectal cancer. Other studies have suggested the bread could also reduce the risk of heart disease.
Although the benefits of whole grains are well known, the biological processes aren't. The researchers fed laboratory mice with both types of bread and analysed their blood afterwards. After eating the wholegrain rye, serotonin levels in the blood were far lower than after eating low-fibre wheat bread.