Suksomboon N, et al. – Researchers analyzed the evidence from randomized, placebo–controlled trials on the impact of vitamin K supplementation on insulin sensitivity. They found that evidence was indicative of nil impact of vitamin K supplementation on insulin sensitivity.

Methods

• Researchers searched MEDLINE, the Cochrane Library, CINAHL, Web of Science, Scopus, clinicaltrials.gov, and clinicaltrialresults.org up to January 2017 and scanned reference lists of related papers.
• They selected randomized controlled trials : comparing vitamin K supplementation with placebo or no treatment and reporting homeostasis model assessment of insulin resistance, fasting plasma glucose, fasting plasma insulin, C-reactive protein, adiponectin, leptin, or interleukin-6 levels.
• Data extraction and study quality assessment were performed independently by two investigators using a standardized data extraction form.
• Any inconsistencies were resolved by a third reviewer.
• They pooled effect estimates using inverse-variance weighted method and assessed heterogeneity by the I² and Q statistic.

Results

• Data reported that a total of eight trials involving 1,077 participants met the inclusion criteria.
• Findings also revealed that a wide variety of participants were enrolled, including older men, postmenopausal women, prediabetic premenopausal women, and participants with a history of diabetes, hypertension, or vascular disease.
• Vitamin K1 and vitamin K2 (MK-4 and MK-7 subtypes) were assessed.
• It was noted that supplementation period ranged from 4 weeks to 3 years.
• Researchers found that vitamin K supplementation did not affect insulin sensitivity as measured by homeostasis model assessment of insulin resistance, fasting plasma glucose, fasting plasma insulin, C-reactive protein, adiponectin, leptin, and interleukin-6 levels.