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Cholecalciferol and 25-hydroxyvitamin D concentrations in adults with cystic fibrosis

CF Centre Ghent University Hospital 5K6
De Pintelaan 185
B9000 Ghent
Belgium
E-mail: eddy.robberecht{at}ugent.be

Dear Sir:

The results obtained in the impressive study by Stephenson et al (1) are surprising and frustrating to desperate clinicians who have not succeeded in increasing serum 25-hydroxyvitamin D concentrations (SVDCs) in their cystic fibrosis (CF) patients. The failure of oral supplements to effect such is widely published (2-4). In search of alternatives, we undertook a retrospective investigation to clarify the relative importance of vitamin D sources and came to remarkably different conclusions (5).

SVDC data (n = 474 measurements) collected annually over 4 consecutive years (2001–2005) from 137 CF patients (mean age: 15.6 y; range: 0.5 mo to 42 y) were retrospectively evaluated. Plotted per month, these values depict an S-shaped curve convex from May to October (sunny) and concave in the following period (dark). Mean values in each period (sunny: 26.6 ng/mL; dark: 17.3 ng/mL) were significantly different from each other; however, this was not the case when values were compared with those of healthy controls during the same period (sunny: 28.6 ng/mL; dark: 18.8 ng/mL). A striking significant relation was found between SVDCs over the 4 y and the amount of sun hours in the preceding months. The SVDC curve constantly paralleled that indicating the hours of sunshine, with a delay of about 2 mo. It is interesting to note that all of these findings were valid in patients with exocrine pancreatic insufficiency and in those with pancreatic sufficiency, although the latter group (n = 12) was too small to determine statistical significance. Another comparison also indicated the importance of the intestinal supply, because no significant difference was found between the SVDCs of 50 CF patients taking a daily oral supplement of at least 800 IU cholecalciferol and those of 50 patients matched for age and month of blood collection who were not taking supplements.

All of these findings suggest that endogenous vitamin D production in the skin, under the influence of sunlight, is an important source of this vitamin for CF patients. Sun exposure during the sunny months of the year should therefore be encouraged. In contrast, we found little evidence of an effect of oral supplements on SVDCs. These conclusions are not universally valid because the amount of sunlight largely depends on geographic latitude. However, under good conditions, sun exposure can be an inexpensive and convenient alternative to supplements for increasing SVDCs in CF patients.

ACKNOWLEDGMENTS

Neither author had a personal or financial conflict of interest.

REFERENCES

1. Stephenson A, Brotherwood M, Robert R, Atenafu E, Corey M, Tullis E. Cholecalciferol significantly increases 25-hydroxyvitamin D concentrations in adults with cystic fibrosis. Am J Clin Nutr 2007;85:1307–11.[Abstract/Free Full Text]
2. Boyle MP, Noschese ML, Watts SL, Davis ME, Stenner SE, Lechtzin N. Failure of high-dose ergocalciferol to correct vitamin D deficiency in adults with cystic fibrosis. Am J Respir Crit Care Med 2005;172:212–7.[Abstract/Free Full Text]
3. Donovan D, Papadopoulos A, Staron R, et al. Bone mass and vitamin D deficiency in adults with advanced cystic fibrosis lung disease. Am J Respir Crit Care Med 1998;158:1892–9.
4. Gronowitz E, Garemo M, Lindblad A, Mellstrom D, Strandvik B. Decreased bone mineral density in normal-growing patients with cystic fibrosis. Acta Paediatr 2003;92:688–3.[Medline]
5. Robberecht E, Vandewalle S, Wehlou C, De Schepper J, Van Biervliet S. Oral vitamin D supplements do not determine vitamin D serum levels in cystic fibrosis. JPEN J Parenter Enteral Nutr 2007;31(suppl):S27–8(abstr).

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