Imbalances in gut microbiota composition have recently been reported in people suffering from metabolic syndrome (MetS). This has led the scientific community to explore the gut microbiota’s contribution to the benefits of lifestyle interventions for improving the hallmarks of MetS and related manifestations.
Previous observational findings have shown that consuming fermented dairy products is related to a healthier lifestyle and greater adherence to the Mediterranean diet.
A new randomized controlled trial, led by Dr. Changhao Sun from the Harbin Medical University in China, has found that yogurt may help ameliorate insulin resistance in obese women with nonalcoholic fatty liver disease and MetS by involving the gut microbiota and metabolic and stress parameters.
The authors randomly administered 220g/day of conventional yogurt (n = 48) or regular whole milk (n = 44) to obese adult women with both nonalcoholic fatty liver disease (NAFLD) and MetS. Anthropometric indices, metabolic parameters, inflammatory cytokines and gut microbiota were assessed at baseline and after 6 months of intervention (liver fat and gut microbiota were measured only in a subsample of 20 individuals from each group).
When compared with milk, yogurt intake led to a drop in the homeostasis model assessment of insulin resistance, fasting insulin and 2-h insulin, alongside a decrease in alanine aminotransferase and liver fat, measured by intrahepatic lipid and hepatic fat fraction.
Moreover, yogurt also led to decreased levels of triglycerides, total cholesterol, vaspin—an adipocytokine with insulin-sensitizing and anti-inflammatory effects—lipopolysaccharide (LPS), fibroblast growth factor 21, tumor necrosis factor-alpha and increased levels of oxidative stress markers including glutathione peroxidase and superoxide dismutase.
Yogurt also led to specific changes in gut microbiota composition with an unknown functional impact.
A statistical model provided a means of elucidating the potential mechanisms by which yogurt consumption improved insulin resistance. In this regard, LPS, inflammatory and oxidative stress markers, serum lipids and liver injury assessed through fat accumulation may all be interconnected and may mediate the benefits of yogurt in the human metabolism.
Altogether, these findings suggest that yogurt may improve insulin resistance, which is a common hallmark of NAFLD and MetS, possibly by reducing serum lipids, inflammation, oxidative stress and LPS, and changing gut microbiota composition.
As such, these findings add to previous epidemiological studies and randomized controlled trials showing the benefits of yogurt intake not only in people with obesity, but also in healthy individuals.
Chen Y, Feng R, Yang X, et al. Yogurt improves insulin resistance and liver fat in obese women with nonalcoholic fatty liver disease and metabolic syndrome: a randomized controlled trial. Am J Clin Nutr. 2019; 109(6):1611-9. doi: 10.1093/ajcn/nqy358.