Vitamin K supplementation for cystic fibrosis

Review question

We reviewed the evidence to see whether supplementing vitamin K in people with cystic fibrosis counteracts the effects of deficiency on blood clotting, bone strength and quality of life in people with cystic fibrosis. We tried to determine the best dose needed to prevent this deficiency.

Background

Cystic fibrosis is an inherited condition which causes disease, most noticeably in the lungs, digestive system and pancreas. In people with cystic fibrosis, the pancreas often does not produce enough enzymes to allow the body to absorb digested food properly and this may also be linked to deficiencies of fat-soluble vitamins like vitamin K. Vitamin K is needed for adequate blood clotting, bone formation and some metabolic functions.

Search date

The evidence is current to: 08 October 2014.

Study characteristics

We included two trials (total of 32 participants) in the review. In one trial (14 children aged 8 to 18 years old) for one month half of the participants were given oral vitamin K supplements at a dose of 1 mg/day and the other half were given 5 mg/day. In the second trial all the 18 volunteers (aged 13 to 35 years) were given 5 mg oral vitamin K supplement or nothing for one month and then they swapped to the other group for another month. Unfortunately, we could not analyse the data from this second trial because the investigators did not report data just from the first part of the trial (only from the end of the trial when all volunteers had been in both groups), so we could not tell if the effects were due to supplements or no supplements.

Key results

Neither trial addressed any of the review's primary outcomes (blood clotting, bone formation and quality of life). Both trials reported that in patients who had low levels of vitamin K measured in the blood and also another laboratory marker of vitamin K (undercarboxylated osteocalcin), these levels returned to the normal range after one month of daily supplementation with 1 mg of vitamin K.

Quality of the evidence

We were satisfied that both trials reported all the outcomes they planned to and that the results were not at risk of being biased due to volunteers dropping out of the trials. We did not have enough details to decide whether results would be affected by the way the trials were set up or in case volunteers could tell which treatment they were receiving (it would be obvious in the trial comparing supplements to no treatment),

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.

Read the full abstract...
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 strategy: 

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.

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