The study from the University of L’Aquila, Italy, assessed the correlation between vitamins D and K deficiency, and patients with Crohn’s disease (CD) and ulcerative colitis (UC). The aim was to assess correlations between the dietary intake of vit K and disease characteristics, including risk of osteoporosis.
The authors conclude that IBD patients often avoid foods naturally high in vit K and vit D for fear of exacerbating their symptoms, however the restriction of milk and dairy products results in an inadequate intake of calcium and vitamin D, and limiting consumption of vegetables can lead to a possible shortage of vit K.
The report states: “A high prevalence of patients inadequate [vitamin K] intake would suggest an additional therapeutic target for the prevention of osteoporosis, and possibly inflammation, in IBD.”
Vitamin D and Vitamin K in IBD
Vit D supplements are an established part of the therapeutic strategy targeted at IBD patients.
Vit K supplementation is advised in bone and inflammatory rheumatic disease, chronic renal failure, and for the prevention of vascular calcification and cardiovascular disease, however, the authors of the new study note: “It is hardly mentioned in the nutritional guidelines for IBD patients. This attitude should change in order to reduce the adjunctive risk factor of osteoporosis in already high-risk patients, prevent coagulation defects and possibly help modulate inflammatory responses in IBD.”
Patients with IBD are at an increased risk of osteopenia and osteoporosis, where prevalence approaches 50% risk in Crohn’s disease (CD) patients and 30% in ulcerative colitis (UC) patients.
The pathogenesis of IBD-associated bone loss is notably multifactorial and includes deficits of micronutrients, including calcium, vit D and vit K. The inadequate intake of calcium and vit D is frequent, and supplements are often prescribed.
Recently, attention has been focused on the role of vit K in bone well-being in IBD patients, however, while the relationship between calcium, vit D and bone metabolism is well documented, the clinical relevance of vit K remains less clear. That said, some studies have shown that inadequate intake of vit K can promote hip fractures and low blood concentrations in IBD.
Dietary sources of vit D and calcium usually come via milk and milk derivatives, however, lactose-containing foods are often malabsorbed by a large part of the adult population. The authors of the new study note: “The fear that lactose-containing foods induce or worsen abdominal symptoms, bloating, and diarrhea, leads to unnecessary restrictions on their intake. This is not rare even in the absence of documented lactose malabsorption, and has been documented in the general population and patients affected by irritable bowel syndrome.”
Dietary supply of vit D has been extensively studied in IBD patients, however, few data are available on vit K. The authors state: “The inadequate dietary intake of Vitamin D and Vitamin K is an easily reversible factor favouring IBD-associated bone loss, but data on Vitamin K are lacking.”
The study comprised of a quantitative food frequency questionnaire completed by 193 IBD patients (89 Crohn’s disease and 104 ulcerative colitis) who visited the University of L’Aquila IBD referral centre between January 2016 and January 2020. Dietary data from IBD patients were compared with those of the healthy family members accompanying the patients and staff members, making up 199 controls.
Information was collected by a dietitian through patient completion of a food frequency checklist, focusing on green leafy vegetables, including spinach, iceberg lettuce, chicory, beets, turnip tops and rocket salad, as well as eggs, as the main contributors to vit K intake.
The study found that vit D intake was inadequate both in the IBD and control patients (53.1% RDA, and 63.2% RDA, respectively). Conversely, the mean vit K intake was less than adequate in IBD (78.7% RDA), and high in controls (138.8% RDA).
Diets were found to be severely lacking vit K in 40% of UC and 49% of CD patients, more so in females and those with active disease.
The intake of vit D was not significantly lower in UD than that in CD patients, however, the opposite was observed for vit K. The authors conclude: “The diet lacks the micronutrients involved in bone wellbeing in a large proportion of IBD patients.
Evaluating Vitamin D
Vit D status is estimated by dosing 25-hydroxy Vitamin D3, however, the authors of the study note that the issue is more complex for vit K, as direct serum phylloquinone (the main dietary form of vitamin K) measurements do not offer a reliable evaluation of vit K levels.
The authors also note that blood concentrations are better markers of daily intake than of total body storage, and so indirect evaluations based on vit K-dependent enzymes are preferred yet are not widely available.
Isolated abnormal prothrombin time (PT) - a coagulation test result that indicates limited clotting ability - can be suggestive of vit K deficiency and prompt supplementation requirement. However, this new study acknowledges that PT does not represent an effective biomarker of vit K deficiency, as only the proportion of vit K that is not used by liver biosynthesis is available for bone metabolism.
Thus, the authors conclude: “Vit K deficiency impairs bone metabolism before any effect on coagulation is observed; indeed, bone is susceptible to less marked vit K shortage than liver function.
“A shortage of vit K was likely present in a considerable proportion of IBD patients, however, the dosage of vit K-dependent enzymes in IBD patients needs reviewing in order to confirm the hypothesis.”
“Low Vitamin K and Vitamin D Dietary Intake in Patients with Inflammatory Bowel Diseases”
Authors: Filippo Vernia, Giorgia Burrelli Scotti, Noemi Sara Bertetti, Giuseppe Donato, Stefano