Effect of vitamin K supplementation on insulin sensitivity: a meta-analysis

Figures & data

Table 1 Characteristics of the studies included in the systematic review

Study	Country of origin	Study design	Duration	Number of participants (VK:C)	Inclusion criteria	Treatment group	Control group	Quality score	Dietary intake and LSM
Yoshida et al,^Citation30 Shea et al^Citation35	USA	DB, P	3 years	452 (229:223)	Men and postmenopausal women aged 60–80 years who did not have diabetes at baseline	K1 500 µg/d + multivitamin + calcium carbonate 600 mg/d + vitamin D 400 IU/d	Multivitamin + calcium carbonate 600 mg/d + vitamin D 400 IU/d	4	Subjects were advised to maintain their usual diet and avoid taking dietary supplements other than those provided throughout the study. Mean rate of adherence with treatment, assessed on the basis of pill counts over 3 years, was 89.1% for the treatment group and 88.5% for the control group.
Kumar et al^Citation31	USA	DB, P	1 years	42 (21:21)	Ambulatory, community-dwelling postmenopausal women (>5 years postmenopausal) with a lumbar spine and proximal femur T-score above −2.0 or above −1.5 if a NOF-defined risk factor was present. Had a self-reported low dietary vitamin K intake	K1 1 mg/d + calcium 315 mg (bd) + D3 200 IU (bd)	PLB + calcium 315 mg (bd) + D3 200 IU (bd)	3	NR
Rasekhi et al^Citation32	Iran	DB, P	4 weeks	82 (39:43)	Premenopausal women with prediabetes defined as IFG (100 mg/dL < FPG <126 mg/dL) or IGT (140 mg/dL <glucose 120 min <200 mg/dL). Aged 22–45 years, BMI 18.5–30 kg/m^2	K1 1,000 µg/d	PLB	4	Participants were asked to maintain their habitual food consumption, body weight, and physical activity. Subjects were not allowed to consume any supplements other than the one provided by investigator.
Koitaya et al^Citation33	Japan	DB, P	1 year	48 (24:24)	Postmenopausal Japanese women aged 50–65 years	K2 (MK-4) 1.5 mg/d	PLB	4	Natto (MK-7 containing fermented soybean) intake was restricted to once or twice a week during study period.
Knapen et al^Citation34	the Netherlands	DB, P	3 years	325 (161:164)	Healthy, nonosteoporotic postmenopausal Caucasians women aged 55–75 years	K2 (MK-4) 45 mg/d	PLB	4	NR
Kristensen et al^Citation36	Denmark	DB, CO	6 weeks	48	Postmenopausal women (>5 years since last menses)	K1 500 µg/d + D3 10 µg/d	PLB + D3 10 µg/d	4	Subjects were allowed to consume their habitual diet.
Fulton et al^Citation37	the Netherlands	DB, P	6 months	80 (40:40)	Community-dwelling people aged ≥70 years with a history of hypertension, diabetes, or previously diagnosed vascular disease.	K2 (MK-7) 100 mcg/d	PLB	4	NR

Abbreviations: bd, twice daily; BMI, body mass index; C, control; CO, crossover; CRP, C-reactive protein; DB, double-blind; FPG, fasting plasma glucose; FPI, fasting plasma insulin; HOMA-IR, homeostasis model assessment of insulin resistance; IFG, impaired fasting glucose; IGT, impaired glucose test; IL-6, interleukin-6; LSM, lifestyle modification; MK-4, menaquinone-4; NOF, National Osteoporosis Foundation; P, parallel; VK, vitamin K; PLB, placebo; NR, not reported; MK-7, menaquinone-7.

Table 2 Summary of outcomes reported in the studies included in the meta-analysis

Author	List of outcomes reported
	HOMA-IR	FPG	FPI	Adiponectin	Leptin	IL-6	CRP
Yoshida et al^Citation30	√	√	√
Kumar et al^Citation31	√	√	√
Rasekhi et al^Citation32	√	√	√	√	√
Koitaya et al^Citation33				√	√
Knapen et al^Citation34				√
Shea et al^Citation35						√	√
Kristensen et al^Citation36						√	√
Fulton et al^Citation37							√

Abbreviations: CRP, C-reactive protein; FPG, fasting plasma glucose; FPI, fasting plasma insulin; HOMA-IR, homeostasis model assessment of insulin resistance; IL-6, interleukin-6.

Figure 1 Flow of study selection.

Figure 2 Mean difference (95% CI) in HOMA-IR, FPG, FPI, leptin, IL-6, and CRP.

Abbreviations: CI, confidence interval; CRP, C-reactive protein; FPG; fasting plasma glucose; FPI, fasting plasma insulin; HOMA-IR, homeostasis model of insulin resistance; IL-6, interleukin-6.

Figure 3 Mean difference (95% CI) in adiponectin.

Abbreviation: CI, confidence interval.

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