The definition of vitamin D deficiency is hampered by the fact that large interlaboratory differences exist in assays for serum 25OHD. In a European multicenter study (SENECA study) Van der Wielen et al. measured wintertime serum 25OHD con­centrations in 824 elderly people (aged 70-75 years) from 11 countries (12 men and 13 women from Italy). Data was collect­ed between December 1988 and March 1989. In a general structured interview conducted in the participant’s home; infor­mation was obtained on potential determinants of vitamin D status: use of dietary supplements, use of sunray lamps, pres­ence of chronic disease, activities of daily living, social isola­tion, and exposure to sunlight. Hours spent outdoors walking, cycling, gardening or other activities were summed to estimate an outdoor leisure time activity score. Questions on sunlight exposure concerned the frequency of going outside during sunny periods and the clothes worn when outdoors during the summer. Town-specific and sex-specific means are reported for the total population under study, along with the proportion of participants with a 25OHD concentration below 30 nmol/L. The results were reported in 1995: 36% of men and 47% of women had 25OHD concentrations below 30 nmol/L. Surpris­ingly, lowest mean 25OHD concentrations were seen in south­ern European countries. Lowest mean concentrations of 25OHD were found in the southern European towns of Greece, Spain, and Italy: 42% of Italian men and 92% of women had 25OHD concentrations below 30 nmol/L. People who used sunlamps and/or vitamin D supplements had much higher 25OHD concentrations than those who did not. Two-thirds of people who used vitamin D supplements and/or sun lamps lived in Norway or in Denmark.

The international “Multiple Outcomes of Raloxifene Evaluation” study, a large prospective intervention trial in postmenopausal women with osteoporosis, offered another opportunity to com­pare vitamin D status and parathyroid function throughout many countries over the world, including Italy. For this study, baseline data were available from 7564 (200 from Italy) post- menopausal women (aged 31-80 yr, mean 66.5 yr) from 25 countries on 5 continents; all women had osteoporosis, i.e. bone mineral density (BMD) at femoral neck or lumbar spine was lower than T-score -2.5, or had 2 vertebral fractures. The prevalence of serum 25OHD below 25 nmol/L differed widely by country and region, being more common in southern Europe and some countries of central Europe (Poland, Slovakia, and Slovenia). The country differences are not explained by season­al and/or age differences in recruitment of the participants. Within Europe there was an unexpected significant positive cor­relation between serum 25OHD and latitude: in particular, Italy was one of the countries with the lower mean levels of serum 25OHD. This finding might be considered surprising since the Mediterranean countries, in general, experience a greater quan­tity of sunny days than do northern European countries. This is usually sufficient in young individuals, but not in elderly women who do not like sun exposure during the hours that are effective for vitamin D synthesis. In addition, one should also consider that the latitude of northern Italy is the same as that of southern Canada, and both places have only a few hours daily of UV irra­diation effective for skin synthesis of vitamin D. Moreover, the widespread consumption of fatty fish provides an excellent source of dietary vitamin D for residents of northern Europe and may explain the lower prevalence of vitamin D deficiency in this region compared with central and southern Europe. This data suggests that although the influence of sunlight exposure is de­tectable when comparing vitamin D status within countries be­tween the winter and summer months, these differences in vita­min D status may be overwhelmed by the influences of vitamin D fortification policies, dietary habits, and the use of vitamin D supplements. Inhabitants of southern Europe stay out of direct sunlight; in addition, time spent outdoors, clothing habits, skin type and pigmentation may influence differences in vitamin D status between countries. In some countries edible oils and fats are vitamin D enriched, and therefore may become important dietary vitamin D sources, especially in wintertime when sunlight exposure is scarce. Vitamin D addition to margarine is compul­sory in Norway, Denmark, the Netherlands, Belgium, and Portu­gal, prohibited in France, and optional but not done in Hungary, Switzerland, Spain, Italy, Portugal, and Greece. Low 25OHD concentrations could largely be explained by attitudes towards sunlight exposure and factors of physical health status, after ex­clusion of users of vitamin D supplements or sunlamps. Prob­lems with daily living activities and wearing clothes with long sleeves during periods of sunshine were strong predictors of low wintertime serum 25OHD concentrations. These findings show that free-living elderly Europeans, regardless of geo­graphical location, are at substantial risk of inadequate vitamin D status during winter and that dietary enrichment or supple­mentation with vitamin D should be seriously considered during this season.
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