Systematic reviewindependent cross-checkabstract checked★ key study I-VEG-105 standard review

Low vitamin K intake linked to unstable warfarin control

Effect of Vitamin K Intake on the Stability of Treatment with Vitamin K Antagonists: A Systematic Review of the Literature.

Overview

Dentali F et al.. Semin Thromb Hemost 2016 · PMID 27232386 · DOI 10.1055/s-0036-1581105

A review of 15 studies (1,838 patients) found unstable control more often in people with LOW vitamin K intake.

Does the study support the specific claim? No · Methodological quality: low

Study explained simply

What did the researchers want to find out?: Review vitamin K intake and VKA stability.
How was the study done?: Systematic review.
How many people, animals or samples were studied?: 15 studies, 1,838 patients.
What was actually found?: Low intake linked to instability; supplements may help unstable patients.
How large was the observed effect?: No pooled estimate.
What do the results mean in everyday life?: Avoiding greens does not make warfarin more stable.
What are the study's limitations?: Narrative; overlapping studies.
What does it say about Elawady's specific claim?: Argues against avoidance; supports consistent intake.
Do the results apply to Germany and Europe?: Universal.
What can explicitly not be concluded from this study?: Cannot give a precise effect size.

What is the role of dietary vitamin K intake and vitamin K supplementation in the stability of VKA therapy?

Study design: Systematic review – Systematic review of observational and interventional studies (Medline, EMBASE)
Population: Patients on vitamin K antagonists
Country: Multiple
Period: Search date not stated in abstract
Sample size: 15 studies, 1,838 patients
Inclusion and exclusion criteria: not stated in abstract

Exposure / intervention: Dietary vitamin K intake; vitamin K supplementation
Comparator: Lower intake / placebo
Endpoints: INR stability, time in therapeutic range
Statistical methods: Narrative synthesis (no pooled estimate reported in abstract)

Results: Observational studies suggest an increased risk of unstable anticoagulation in patients with lower daily vitamin K intake. Daily vitamin K supplementation may be associated with a clinically relevant increase in time in therapeutic range in unstable patients; the effect appears small in unselected populations.
Absolute risks: not reported
Authors' conclusion: The role of supplementation or a diet with controlled vitamin K content remains to be established; larger prospective studies are needed.

No pooled effect; overlapping primary studies with Violi 2016 (A-VEG-17) - not independent confirmation.

Limits the claim: lower vitamin K intake, not higher, is associated with instability.

Franco 2004; Couris 2006 (changes in intake shift INR).

Universal.

Consistent with Violi 2016: avoidance of greens is not supported; consistency matters.

Multidimensional assessment
Multidimensional assessment
Authenticity of the source	verified
Methodological quality	low
Risk of bias	some concerns
Precision of results	not applicable
Directness	direct
Reproducibility	unknown
Consistency with the overall evidence	mixed
Regional transferability	high
Adequacy of the interpretation (by the archive)	not applicable

Large RCTs of dietary counselling strategies.