100% rye bread reduces blood glucose levels by reducing levels of serotonin in the gut. [Photo: Bigstock]

How wholegrain rye bread cuts type-2 diabetes risk

30 June, 2019

Natural Health News — If you are at risk of type-2 diabetes, you might consider switching to your daily loaf from wheat to one made from wholegrain rye.

The consumption of whole grain cereals has been associated with a lower risk of type-2 diabetes, cardiovascular disease and some cancers. How it does this – whether via effects from bioactive compounds contained in whole grains, or the effect that phytochemicals and fibres have on intestinal bacteria – is still the subject of some speculation.

In a new study researchers from the University of Eastern Finland and the International Agency for Research on Cancer (IARC) tested the metabolic effects of consuming an enriched wheat bread against wholegrain rye bread in 15 human volunteers.

For the first four weeks of the study, the participants ate 6 to 10 slices a day of either whole grain rye bread or a white wheat bread enriched with fermented rye bran. In a second 4-week testing period, all participants ate the same amount of rye-free white wheat bread. Otherwise, they didn’t change their diet.

At the end of both testing periods, they gave blood samples, which were analysed by a combination of liquid chromatography and mass spectrometry. In particular the researchers were looking to compare the samples for concentrations of certain metabolites (the end product of metabolism) which might indicate a risk

Serotonin-glucose connection

The consumption of wholegrain rye led to, among other things, significantly lower serotonin concentrations when compared to consumption of the wheat bread. This finding was confirmed in a separate feeding test involving mice.

Serotonin is best known as a neurotransmitter in the brain. However, serotonin produced by the intestines remains separated from the brain, serving various peripheral functions including modulation of gut’s motility. Increased blood serotonin has also been associated with high blood glucose levels.

“Whole grain, on the other hand, is known to reduce the risk of diabetes, and on the basis of these new results, the effect could at least partly be due to a decrease in serotonin levels,” says Academy Research Fellow Kati Hanhineva from the University of Eastern Finland.

The researchers say the findings, published in the American Journal of Clinical Nutrition, may also shed some light on the development of colorectal cancer.

“Some recent studies have found cancer patients to have higher plasma serotonin levels than healthy controls,” Scientist Pekka Keski-Rahkonen from IARC adds.