Vitamin D deficiency represents an important public health problem, especially among elderly people, by increasing the morbimortality. Because of the importance of this, in the year 2001 the "Five Countries Study" was put in place, within the European OPTIFORD project (Towards a strategy for optimal vitamin D fortification). This cross-sectional and observational study aims at knowing the vitamin D status in adolescent and elder women from five European countries, including Spain, according to different dietary and behavioral habits.
This work analyzes the relative contribution of sun exposure and diet to the vitamin D status in 53 Caucasian Spanish elder women (72 +/- 1.6 years), with an autonomous life, participating at the Five Countries Study.
The information was gathered in summer and winter time, by using homologated and validated questionnaires: health status and life style questionnaire; assessment of sun exposure by a standardized test and using a Viospor UV dosimeter (only in summer time); biochemical analysis of 25 hydroxyvitamin D (S-25-OHD) and parathyroid hormone; and questionnaire of frequency of selective intake.
We observed a direct relationship between sun exposure measured with the dosimeter (741 +/- 624 J/m2) and the number of hours outdoors during the measuring week (3.4 +/- 1.9 hours/day) (p < 0.0001). The serum levels of S-25-OHD were higher in summer time than during the winter (40.32 +/- 20.39 nmol/L and 30.08 +/- 17.39 nmol/L, respectively), and 40% of the participants had worse vitamin status in winter as compared with summer time (p < 0.001). During the summer time, vitamin D deficiency (S-25-OHD < or = 25 nmol/L) affected 28% of the population, being virtually twice as much during the winter time. The higher the sun exposure, as assessed by the dosimeter, the higher the value of S-25-OHD, with clear differences between participants in the S-25-OHD < or = 25 nmol/L group and those in the S-25-OHD > 50 nmol/L (p = 0.01). There is also a direct association between the number of hours outdoors and S-25-OHD (p = 0.09), with differences between the participants in the S-25-OHD < or = 25 nmol/L group and the S-25-OHD > 50 nmol/L group. In more than 95% of the sample, mean dietary intakes of vitamin D (5.17 +/- 4.84 microg/day in summer time and 4.70+/- 4.72 microg/day in winter time), the main source of which being fish, did not cover the Recommended Allowances. We did not observe a relationship between the dietary intake and blood levels of vitamin D. By contrast, those participants taking vitamin D supplements presented higher S-25-OHD levels (summer = 69.64 nmol/L and winter = 55 nmol/L) than those not consuming it (summer = 36.83 nmol/L and winter = 25.82 nmol/L) (psummer =0.0003 and p winter < 0.001).
The deficient status of vitamin D among the elderly female population has to be corrected, whenever possible, with appropriate sun exposure and an increase in vitamin D intake through the diet, assessing at each particular case the benefits of pharmacological supplementation.