The Differential Effects of Vitamin K Across Glycaemic Outcomes in Prediabetes and Type 2 Diabetes Mellitus

TL;DR

This study finds that vitamin K may help lower blood sugar and insulin resistance in people with prediabetes or type 2 diabetes, but more research is needed.

Contribution

The study provides the first meta-analysis of vitamin K's effects on glycaemic outcomes in clinical trials.

Findings

Vitamin K significantly reduced fasting blood glucose, HbA1c, and insulin resistance.

Low doses of vitamin K2 and K1 were linked to specific improvements in HbA1c and HOMA-IR.

Short-term interventions (<12 weeks) were associated with reduced insulin resistance.

Abstract

Background: Vitamin K has emerged as a promising regulator of glucose metabolism in preclinical studies. There is, however, scant evidence to support this promising potential in a clinical setting. Aim: The aim of this study was to confirm the effects of vitamin K supplementation on glycaemic parameters such as fasting blood glucose (FBG), fasting insulin (FI), glycated haemoglobin (HbA1c), insulin resistance (HOMA-IR), and homeostatic model of beta cell function (HOMA-β) across randomised controlled trials (RCTs). Materials and Methods: This meta-analysis used evidence from PubMed, Scopus, and manual screening. Only RCTs were considered for this meta-analysis of interventional studies. The Meta online tool was used to analyse data, with the results reported as either the mean or the standardised mean difference (SMD), alongside 95% confidence intervals (CI). Results: Only eight RCTs were found relevant and analysed; the age of those in the vitamin K group was 50.58 ± 6.91 years, and in the control group, it was 48.19 ± 5.41. The evidence showed a significant reduction in FBG, SMD = −0.22 (−0.39 to −0.05), HbA1c, MD = −1.00%, 95% CI (−1.92 to −0.07), and HOMA-IR, MD = −0.63, 95% CI (−1.20 to −0.06). However, no effect was observed on insulin (SMD = −0.39, 95% CI: −0.91 to 0.13, p = 0.15) and HOMA-β (MD = 6.56, 95% CI (−3.89 to 17.01), p = 0.2184. Low doses of vitamin K2 and vitamin K1 were associated with reduced HbA1c and HOMA-IR, respectively. An intervention of less than 12 weeks was associated with reduced HOMA-IR. Conclusions: This study showed a significant decrease in FBG, HbA1c, and HOMA-IR without affecting insulin or HOMA-β. Nevertheless, the limited number of trials with moderate quality warrants larger, longer-term RCTs with rigorous methodology and direct comparisons of vitamin K isoforms to better assess therapeutic potential.

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