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Whole grain intake linked to improved stool, gut microbiota
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By comparing a whole grain-based diet and a refined grain-based diet, researchers showed a modest improvement in stool, gut microbiota and immune response in those who consumed more whole grains.
“We found modest effects of whole grain consumption on gut microbiota. They increased, one, ‘good bacteria’ that are known to have anti-inflammatory effect and, two, bacterial product (short chain fatty acids that have been related to regulation of the immune system),” Simin Nikbin Meydani, DVM, PhD, director of the nutritional immunology laboratory at the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University in Boston told Healio Gastroenterology. “This was associated with modest improvement with measures of immune function that are related to ability to fight against a pathogen. In addition , we showed that whole grain improved bowel movement.”
Meydani and colleagues narrowed their applicants to 81 participants: 40 who received the refined grain diet and 41 who received the whole grain diet. These participants underwent a 2-week run-in period of provided food before consuming a fully provided diet for 6 weeks.
Participants recorded all food intake as well as their GI symptoms on a weekly basis. Researchers collected stool, blood and saliva samples at baseline and again at the end of the diet intervention. There was no difference in sex, age, BMI, race, education, marital status or occupation between the groups at baseline and participants maintained weight through the dietary intervention.
Upon completion, results showed increased stool weight (P = .0001), stool frequency (P = .02) in the whole grain group and no change in the refined grain group. Researchers also noted trends toward decreasing Enterobacteriaceae abundance and increase in Lachnospira and Roseburia abundance in the whole grain group.
Though there was not a difference in all T cell counts, there was a difference in the change of the percentage of total terminal effector memory T cells between the whole and refined grain group (P = .03). Additionally, researchers noted a modest positive correlation between TNF-alpha and total alkylresorcinols (P = .04), which they suggested was due to increased whole grain intake.
“All food was provided to participants, allowing them to maintain their body weight constant, thus eliminating the confounding effect of weight loss associated with increasing fiber consumption on immune and inflammatory markers. Additionally, our study incorporated markers of diet adherence and whole grain consumption, allowing us to more confidently determine the effect whole grains have on the gut microbiota and inflammatory responses,” Meydani said in a press release,
The researchers suggested this controlled diet method might have a greater impact on patients already diagnosed with inflammatory conditions.
“There is a body of evidence suggesting that replacing refined grains with whole grains will lead to better health. Results from our study supports this by showing that it promotes better gut microbiota, immune response, bowel movement and improved energy balance,” Meydani said in an interview. – by Katrina Altersitz
Disclosure: This study was supported by the Bill Institute of Health and Nutrition and General Mills Inc. The researchers report no relevant financial disclosures.
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