Higher vitamin K intake is associated with better INR control and a decreased need for INR tests in long-term warfarin therapy

Potential Drug-Nutrient Interactions of 45 Vitamins, Minerals, Trace Elements, and Associated Dietary Compounds with Acetylsalicylic Acid and Warfarin-A Review of the Literature

In cardiology, acetylsalicylic acid (ASA) and warfarin are among the most commonly used prophylactic therapies against thromboembolic events. Drug-drug interactions are generally well-known. Less known are the drug-nutrient interactions (DNIs), impeding drug absorption and altering micronutritional status. ASA and warfarin might influence the micronutritional status of patients through different mechanisms such as binding or modification of binding properties of ligands, absorption, transport, cellular use or concentration, or excretion. Our article reviews the drug-nutrient interactions that alter micronutritional status. Some of these mechanisms could be investigated with the aim to potentiate the drug effects. DNIs are seen occasionally in ASA and warfarin and could be managed through simple strategies such as risk stratification of DNIs on an individual patient basis; micronutritional status assessment as part of the medical history; extensive use of the drug-interaction probability scale to reference little-known interactions, and application of a personal, predictive, and preventive medical model using omics.

Vitamins K1 and K2: The Emerging Group of Vitamins Required for Human Health

Objective

To review the evidence for the use of vitamin K supplementation in clinical conditions such as osteoporosis, vascular calcification, arthritis, cancer, renal calculi, diabetes, and warfarin therapy.

Quality of Evidence

PubMed was searched for articles on vitamin K (K1 and K2) along with books and conference proceedings and health conditions listed above. Level I and II evidence supports the use of vitamins K1 and K2 in osteoporosis and Level II evidence supports vitamin K2 in prevention of coronary calcification and cardiovascular disease. Evidence is insufficient for use in diabetes, arthritis, renal calculi, and cancer.

Main Message

Vitamin K2 may be a useful adjunct for the treatment of osteoporosis, along with vitamin D and calcium, rivaling bisphosphonate therapy without toxicity. It may also significantly reduce morbidity and mortality in cardiovascular health by reducing vascular calcification. Vitamin K2 appears promising in the areas of diabetes, cancer, and osteoarthritis. Vitamin K use in warfarin therapy is safe and may improve INR control, although a dosage adjustment is required.

Conclusion

Vitamin K supplementation may be useful for a number of chronic conditions that are afflicting North Americans as the population ages. Supplementation may be required for bone and cardiovascular health.

Nutritional management of a patient with obesity and pulmonary embolism: a case report

Background

The aim of this case report is to discuss the issue of nutritional therapy in patients taking warfarin. Patients are often prescribed vitamin K free diets without nutritional counseling, leading to possible health consequences.

Case presentation

A 52-year-old woman with obesity and hypertension was prescribed a low calorie diet by her family doctor in an effort to promote weight loss. After a pulmonary embolism, she was placed on anticoagulant therapy and on hospital discharge she was prescribed a vitamin K free diet to avoid interactions. Given poor control of her anticoagulant therapy, she was referred to our Nutritional Unit outpatients’ service.

Conclusions

This case illustrates the importance of a thorough medical nutrition assessment in the management of patients with obesity and the need for a change in the dietary approach of nutritional therapy in the management of vitamin K anticoagulant therapy. In patients taking warfarin, evidence suggest that the aim of nutritional therapy should be to keep dietary intake of vitamin K constant.

Development of neuro-fuzzy model to explore gene-nutrient interactions modulating warfarin dose requirement

AIM

To investigate the influence of alterations in vitamin K (K1, K2 and K3) in modulating warfarin dose requirement.

PATIENTS & METHODS

Reverse phase HPLC to determine the plasma vitamin K; PCR-RFLP to detect polymorphisms; and the neuro-fuzzy model to predict warfarin dose were used.

RESULTS

The developed neuro-fuzzy model showed a mean absolute error of 0.000024 mg/week. CYP2C9*2 and CYP2C9*3 mediated warfarin sensitivity was observed when vitamin K is in high and low tertiles, respectively. VKORC1-1639G>A exhibited warfarin sensitivity in all combinations. Higher vitamin K1 was observed in CYP4F2 V433M polymorphism. The requirement of warfarin is low in GGCX 8016 GG genotype compared with GA and AA genotypes.

CONCLUSION

Vitamin K profile along with genetic testing ensures precision in warfarin dose optimization.

Avoidance of Vitamin K-Rich Foods Is Common among Warfarin Users and Translates into Lower Usual Vitamin K Intakes

BACKGROUND

Warfarin users should aim for stable daily vitamin K intakes. However, some studies report that patients are often advised to avoid eating green vegetables. Whether this advice impacts vitamin K intakes is unknown.

OBJECTIVE

Our aim was to describe the nature and sources of vitamin K-related dietary recommendations that patients received at the initiation of warfarin therapy, assess their adherence to these recommendations, and examine whether usual vitamin K intakes vary according to these recommendations.

DESIGN

We conducted a retrospective cohort study with patients enrolled in the Québec Warfarin Cohort Study. Patients were asked to report dietary recommendations they had received at warfarin initiation and their adherence to these recommendations. Usual vitamin K intakes were assessed using a validated semi-quantitative food frequency questionnaire.

PARTICIPANTS/SETTING

Three hundred seventeen patients aged 36 to 97 years who initiated warfarin between 2011 and 2012 and were treated for 12 months or longer with a target international normalized ratio range of 2.0 to 3.0 or 2.5 to 3.5.

STATISTICAL ANALYSES PERFORMED

Patients were classified according to vitamin K-related recommendations reported: limit or avoid vitamin K-rich foods; aim for stable consumption of vitamin K-rich foods; or no vitamin K-related advice. A one-way analysis of covariance was used to compare mean usual vitamin K intakes between patients after adjustment for covariates.

RESULTS

Most patients (68%) reported being advised to limit or avoid vitamin K-rich foods, particularly green vegetables, 10% reported being advised to aim for stable consumption of vitamin K-rich foods, and 22% did not recall receiving any vitamin K-related recommendation. Mean usual vitamin K intakes of patients adhering to the recommendation to limit or avoid vitamin K-rich foods was 35% to 46% lower than those of other patients (P<0.001), a difference resulting almost entirely (82%) from a lower consumption of green vegetables.

CONCLUSIONS

In contrast with current dietary recommendation, most warfarin users reported avoiding vitamin K-rich foods, which translated into lower usual vitamin K intakes.

Association Between Usual Vitamin K Intake and Anticoagulation in Patients Under Warfarin Therapy

This study aimed to explore the correlation between usual vitamin K intake and response to anticoagulant therapy among patients under warfarin therapy. We conducted a retrospective survey of patients (n = 50) on continuous warfarin therapy. Clinical information and laboratory parameters were sourced from medical records. Anticoagulant effect was evaluated by using the percent time in therapeutic range (TTR) and the coefficient of variation (CV) of International normalized ratio (INR). Dietary vitamin K intake was assessed using a semi-quantitative food frequency questionnaire that has been developed for the purpose of assessing dietary intake of vitamin K. A total of 50 patients aged between 21 and 87 years were included in the study. The mean vitamin K intake was 262.8 ± 165.2 µg/day. Study subjects were divided into tertiles according to their usual vitamin K intake. The proportion of men was significantly higher in second and third tertile than first tertile (p = 0.028). The mean percent TTR was 38.4 ± 28.4% and CV of INR was 31.8 ± 11.8%. Long-term warfarin therapy group (≥ 3 years) had a higher percentage of TTR as compared to the control group (< 3 years) (p = 0.046). No statistically significant correlation was found between usual vitamin K intake and percent TTR (p > 0.05). In conclusion, no significant association was observed between usual vitamin K intake and anticoagulant effects. Further studies are required to consider inter-individual variability of vitamin K intake. Development of assessment tools to measure inter-individual variability of vitamin K intake might be helpful.