Background: Cystic fibrosis is a genetic disorder which can lead to multiorgan dysfunction. Malabsorption of fat and fat-soluble vitamins (A, D, E, K) may occur and can cause subclinical deficiencies of some of these vitamins. Vitamin K is known to play an important role in both blood coagulation and bone formation. Supplementation with vitamin K appears to be one way of addressing the deficiency, but there is very limited agreement on the appropriate dose and frequency of use of these supplements.
Objectives: To assess the effects of vitamin K supplementation in people with cystic fibrosis and to determine the optimal dose and route of administration of vitamin K for both routine and therapeutic use.
Search methods: We searched the Cochrane Cystic Fibrosis and Genetic Disorders Group's Trials Register comprising references identified from comprehensive electronic database searches and handsearches of relevant journals and abstract books of conference proceedings. Most recent search: 08 October 2014.
Selection criteria: Randomised and quasi-randomised controlled trials of all preparations of vitamin K used as a supplement compared to either no supplementation (or placebo) at any dose or route and for any duration, in children or adults diagnosed with cystic fibrosis (by sweat test or genetic testing).
Data collection and analysis: Two authors independently screened papers, extracted trial details and assessed their risk of bias.
Main results: Two trials (total of 32 participants) each lasting one month were included in the review and were assessed as having a moderate risk of bias. One was a dose-ranging parallel group trial in children (aged 8 to 18 years); and the other (with an older cohort) had a cross-over design comparing supplements to no treatment, but no separate data were reported for the first intervention period. Neither of the trials addressed any of the primary outcomes (coagulation, bone formation and quality of life). Both trials reported the restoration of serum vitamin K and undercarboxylated osteocalcin levels to the normal range after one month of daily supplementation with 1 mg of vitamin K.
Authors' conclusions: Evidence from randomised controlled trials on the benefits of routine vitamin K supplementation for people with CF is currently weak and limited to two small trials of short duration. However, no harm was found and until further evidence is available, the present recommendations should be adhered to.