Supplementing the high-fat diets of lab rats with freeze-dried blueberry powder appeared to improve the health of the gut by improving the integrity of the gastrointestinal tract and reducing the ‘leakage’ of endotoxins like lipopolysaccharide (LPS) into the blood.
Blueberry supplementation was also associated with improvements in sensitivity to insulin in high-fat fed rats, according to data published in the Journal of Nutrition.
“[W]e show for the first time, to our knowledge, that blueberry-induced reductions in inflammation and insulin resistance in [high fat]-diet–fed rats were found in conjunction with compositional changes in the gut microbiota and improved gut integrity. These changes may have prevented LPS translocation, resulting in reduced systemic inflammation and improved hepatic insulin sensitivity in [high fat]-diet–fed rats,” wrote scientists from the University of Georgia.
“Thus, our study provides further support that blueberry may reduce obesity-related inflammation and insulin resistance.”
Blueberry benefits
The study adds to the ever-growing body of science supporting blueberries and the polyphenols they contain for gut health and inflammation. A 2013 study published in the Journal of Agricultural and Food Chemistry indicated that blueberry powder may selectively boost levels of bifidobacteria in the gut.
In addition, a review paper published last year in the Journal of Functional Foods concluded: “According to the literature, the evidence suggests that several species of blueberries in the genus Vaccinium and their isolated compounds are potential contributors to the regulation of glucose, lipid metabolism and improvement of inflammation.”
Study details
The Athens, GA-based researchers fed male rats low-fat, high-fat or high-fat plus blueberry powder diets for eight weeks. The blueberry powder was provided by the US Highbush Blueberry Council and was a 50-50 blend of Tifblue/Rubel blueberries.
The data showed that compared to the other two diet groups consumption of the blueberry powder led to increases in the abundance of Gammaproteobacteria, especially the Pasteurellales order, including the genuses Actinobacillus and Aggregatibacter.
“Despite being traditionally thought to be proinflammatory, increases in Proteobacteria, especially Gammaproteobacteria, have been reported in association with metabolic improvements, notably after Roux-en-Y gastric bypass in humans and animals,” explained the researchers. “In these studies, similarly to our results, the abundance of Aggregatibacter was significantly increased.”
In addition, blueberry supplementation attenuated changes in the height of the villi in the ileum that occurred in the high-fat diet only animals, said the researchers.
Markers of inflammation were also increased in the high-fat diet-only animals, compared to the low-fat group, but these increased were normalized by blueberry powder consumption. Markers of insulin sensitivity were improved in the blueberry-fed animals, added the researchers.
“[W]e used a rodent model to test our hypothesis and the results cannot be directly extrapolated to humans due to differences in gut microbiota and physiology,” they noted. “[And] although we showed that metabolic improvements with blueberry supplementation were found in association with compositional changes in the gut microbiota, the use of germ-free models would be needed to conclusively show that the gut microbiota is responsible for changes in inflammation and insulin sensitivity.”
The study was supported by a grant from the US Department of Agriculture.
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Source: Journal of Nutrition
Volume 148, Issue 2, Pages 209–219, doi: 10.1093/jn/nxx027
“Blueberry Supplementation Influences the Gut Microbiota, Inflammation, and Insulin Resistance in High-Fat-Diet–Fed Rats”
Authors: S. Lee et al.