Effects of kefir consumption on cardiometadebolic risk factors: A
systematic review and meta-analysis of randomized controlled trials
Abstract
Background. Fermentation of lactose in milk by bacteria and yeasts
naturally present in kefir grains produces a beverage that has been
suggested to have cardiovascular benefit. This systematic review and
meta-analysis of randomized controlled trials (RCTs) aimed to evaluate
the effects of this kefir beverage on cardiometabolic risk factors.
Methods. Literature search utilised PubMed, Scopus, ISI Web of Science,
and Google Scholar for the articles published from inception until June
2021. Cardiometabolic risk indices extracted included insulin and
insulin resistance (HOMA_IR), total cholesterol (TC), triglyceride
(TG), high-density lipoprotein cholesterol (HDL-C), low-density
lipoprotein cholesterol (LDL-C), fasting blood sugar (FBS), haemoglobin
A1c (HbA1c) and body weight (BW). In total, six RCTs (314 subjects) were
selected for the meta-analysis. Inverse-variance weighted mean
difference (WMD) with a 95% confidence interval (CI) was calculated for
the mean changes in TC, TG, HDL-C, LDL-C, FBS, HbA1c and BW compared to
baseline. A random effects model was used to estimate the pooled WMD.
Results. Kefir intake significantly reduced fasting insulin (WMD:-3.69
micro-IU/mL,95% CI:-6.30 to -1.07,p=0.006,I2=0.0%) and HOMA-IR
(WMD:-2.56,95%CI:-3.82 to-1.30, p<0.001,I2=19.4%). No effect
on TC (WMD:-9.30mg/dL,95%CI:-20.00 to 1.39,p=0.088), TG (WMD:-1.35
mg/dL,95%CI:-13.28 to 10.58,p=0.824), HDL-c (WMD:0.70mg/dL,
95%CI:-1.30 to 2.71,p=0.491), LDL-C (WMD:-0.71mg/dL, 95%CI:-13.16 to
11.72, p=0.910), FBS (WMD: -2.73 mg/dL, 95%CI: -7.56 to 2.09,p=0.267),
HbA1c (WMD:-0.58 %, 95%CI: -1.79 to 0.61,p=0.339) or body weight
(WMD:-0.78 kg, 95%CI: -2.75 to 1.19,p=0.439) were found for kefir
treatment. Conclusion. Kefir has a beneficial effect on decreasing
insulin resistance; however, no effect was seen on BW, FBS, HbA1C or the
lipid profile.