Past studies show that whole grain consumption can help in maintaining a healthy gut. It also reduces colorectal cancer risk and prevents type 2 Diabetes. However, biological mechanisms at play are unclear. Coming to positive impact of wholegrain on human gut health, recent studies point to effect on metabolites, molecules that are formed and utilized during metabolic processes. Further studies show how wholegrain wheat and rye consumption affects gut metabolism by affecting plasma/blood serotonin levels. Results of research have been published in The American Journal of Clinical Nutrition.
Scientists analyzed impact of wholegrain on blood metabolite concentration in humans and mice in a two-part study. The 15 adults who participated in the first part were given 6 to 10 pieces of low-fiber wheat bread each day for 4 weeks. For another 4 weeks, they were given 6-10 pieces of wholegrain wheat or rye bread each day supplemented with rye fiber. No other diet alterations were made by participants.
Blood samples from all participants were collected on completion of both 4-week periods. Analysis showed that addition of wholegrain rye had led to significantly lower levels of serotonin in plasma, as compared to when they had consumed low-fiber white bread. Second part of the study included finding out if introduction of cereal fiber in diet can have an impact on serotonin levels in intestines produce. Gut serotonin regulates gut motility and ability of muscles of gastrointestinal tract to contract and relax, allowing food to pass smoothly. The mice were given additional cellulose flour and wheat or rye bran for 9 weeks. Those fed wheat or rye bran showed lower serotonin concentration in colon.
This shows that wholegrain consumption prevents diabetes, as high blood serotonin concentration in linked to high blood sugar, said co-author of study Kati Hanhineva. Also, people with higher blood serotonin concentration are more often seen to have cancer. Incorporation of wholegrain rye bread in diets leads to lower taurine levels in blood. Taurine is present in bile and some other biological fluids and many tissues lower levels of glycerophospholipid and glycerophosphocholine. About 15 phytochemicals were detected in blood of those who had consumed wholegrain daily. Scientists said that further studies are required to fully understand the associations and mechanisms.