Effects of kefir or milk supplementation on zonulin in overweight subjects.

Increased intestinal permeability has been shown to be involved in several diseases associated with low-grade chronic inflammation, including obesity and metabolic syndrome. In the last decade, growing evidence shows the beneficial effects of probiotic-containing food supplementation on these conditions. In this crossover intervention study on 28 asymptomatic overweight adults, we tested the effects of a 3-wk kefir supplementation compared with a 3-wk milk supplementation on serum zonulin levels. The effects on serum glucose, triacylglycerols, low-density lipoproteins, high-density lipoproteins, total cholesterol, markers of inflammation (C-reactive protein and adiponectin), anthropometric variables, mood, and appetite were also determined. Kefir supplementation resulted in a greater improvement of serum zonulin levels (F = 6.812, η2 = 0.275), whereas a significant yet similar improvement in lipid profile and serum glucose levels was found in both supplementations. Positive mood was slightly but significantly enhanced with kefir supplementation, and reduced with milk supplementation. The C-reactive protein, adiponectin, and appetite were unaffected. In conclusion, supplementation with both dairy products had health beneficial effects, but only kefir showed an effect on the intestinal barrier dysfunction marker.

Characterization and stability of lactobacilli and yeast microbiota in kefir grains.

Characterization and stability of lactobacilli and yeasts from kefir grains using culture-dependent and culture-independent methods were investigated in this study. Culture-dependent analysis, followed by sequencing of 16S ribosomal DNA for bacteria and 26S rRNA gene for yeasts, revealed 3 different species of lactobacilli and yeasts, respectively. The most frequently isolated bacterial species were Lactobacillus kefiranofaciens ssp. kefirgranum, Lb. parakefiri, and Lb. kefiri, whereas yeasts belonged to Kluyveromyces marxianus, Kazachstania exigua, and Rhodosporidium kratochvilovae. This study is the first to report on the presence of R. kratochvilovae in kefir grains. On the other hand, PCR-denaturing gradient gel electrophoresis in the culture-independent method showed that the dominant microorganisms were Lb. kefiranofaciens ssp. kefirgranum, Kl. marxianus and Ka. exigua, but did not reveal bands corresponding to Lb. parakefiri, Lb. kefiri, or R. kratochvilovae. Our results support the necessity of combining more techniques for detailed and reliable study of microbial communities in kefir grains. Another interesting finding confirmed that the detected dominant microbiota of kefir grains is very stable and did not change over experimental time. This finding is important to ensure consistent product quality.