Whole grain consumption may change intestinal serotonin production

A study published in The American Journal of Clinical Nutrition suggests that adults consuming whole grain rye may have lower plasma serotonin levels than people eating low-fiber wheat bread. In a study conducted by the University of Eastern Finland and the International Agency for Research on Cancer (IARC), the consumption of cereal fiber from rye or wheat was also found to reduce serotonin levels in the colon of mice.

For the first four weeks of the study, the participants ate six to 10 slices a day of low-fiber wheat bread, and then another four weeks the same amount of whole grain rye bread or wheat bread supplemented with rye fiber. Otherwise, they didn’t change their diet. At the end of both periods, they gave blood samples, which were analyzed by a combination of liquid chromatography and mass spectrometry. The researchers then compared their plasma metabolite profiles between the different diet periods.

The consumption of whole grain rye led to, among other things, significantly lower serotonin concentrations when compared to consumption of low-fiber wheat bread. The researchers also tested in mice whether the addition of cereal fiber to the diet changes serotonin production in the intestine. The diet of the mice was supplemented for nine weeks with rye bran, wheat bran, or cellulose flour. The mice receiving rye or wheat bran had significantly lower serotonin in their colon.

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.

The researchers concluded that considering the results, the health benefits of whole grain cereals may be linked, at least in part, to the alteration of serotonin production in the intestines, where the majority of the body’s serotonin is produced.

Abstract