BMC Public Health 2009, 9:22 http://www.biomedcentral.com/1471-2458/9/22 Table 2: Mean 25(OH)D according to sunbathing habits. Avoids sun Arms/face Whole body P value (ANOVA) Arms/face vs. avoids sun† Whole body vs. avoids sun† Arms/face vs. whole body† 25(OH)D in summer (nmol/L) 25(OH)D in winter (nmol/L) N* 36 66 206 Mean 44.7 54.7 63.1 P < 0.0001 10.1 (1.8–18.3); p = 0.01 18.4 (11.2–25.6); p < 0.001 8.4 (2.7–14.0); p = 0.001 SD 1.9 2.0 1.3 N* 40 78 240 Mean 33.5 40.6 46.3 P < 0.0001 7.0 (0.5–13.6); p = 0.03 12.8 (7.1–18.6); p < 0.001 5.8 (1.4–10.1); p = 0.006 SD 1.9 1.5 1.0 * 10 subjects did not provide their sun-bathing habits data † Post-hoc analysis using Tukey test; presented as differences in mean (95% CI); p value erly situated countries but falls short if compared with vitamin D levels in Belgium, France, Switzerland and the US [7,7,14,18,26,29-33] (Table 3). Our summer 25(OH)D is the lowest in this comparison, which corre- sponds well with the latitude effect. The fact that there is a low proportion of vitamin D supplement users in Estonia and the diet here is also scarce in natural sources of vita- min D (such as fish or fish products) [35] makes the pop- ulation largely dependent on the vitamin D stores accumulated during the sunny season. In a country popu- lating an even higher latitude, Norway, a study showed that 40% of the population regularly uses cod-liver sup- plements, almost 60% consumes fish liver products and 57% other vitamin D supplements, beside cod liver oil [36]. This might explain why Norway, despite being located at 65–71 N is one of the countries with the highest vitamin D levels in Europe. The proportion of 25(OH)D deficiency and insufficiency in our study population is comparable with other coun- tries (table 3) during different seasons even though it is geographically the highest northern country in the com- parison after Finland. However we consider the percent- ages too high to be satisfactory, as there is still a large proportion of the population who especially during win- ter are at an increased health risk. Addressing these short- comings is important as the health risks include diseases like osteoporosis, rickets and with some evidence support- ing benefits or risk reductions also for several types of Table 3: 25(OH)D status in population studies of adults (15+) in the order of latitude. Location Latitude Method N Vitamin D (nmol/L), mean and/or range Deficiency % <25 nmol/L Insufficiency % <50 nmol/L New Zealand [30] Japan [31] US [32] Italy [14] Switzerland [33] France [7] Germany [29] Belgium [18] Estonia Finland [26] 35–47S RIA Diasorin 2946 35 N RIA Disaorin 25–47 N RIA Disaorin 40 N RIA Disaorin 46–47 N CPB Amersham 43–51 N RIA Incstar 49 N RIA Incstar 50 N 59 N 60 N ChL Diasorin RIA Disaorin RIA Incstar 197 18462* 90 3276 1569 415 126 367 328 Population representation (subjects per capita) 1:1,400 1:647,000 1:16,200 1:645,000 1:2,300 1:39,000 1:199,000 1:82,000 1:3,600 1:16,000 * Two different seasonal sub-populations; ** level of <30 nmol/L used to define deficiency; *** own specific cut-off for insufficiency (based on PTH curve) was used; † data from October to June (no summer months); †† no official data in paper (calculated from a figure); ††† level of <37.5 nmol/ L was defined as insufficient; ND – no data. summer 67 79 62–90 84 ND ND 67–70 ND 59 ND winter 44 38 60–79 43 50 † 48 44 46 61 (43–94) 40–45 summer winter summer winter 0–10 48 ND 1–3 2 ** ND ND ~5 †† ND <1 ND ND 1–5 18 ** 6 † 14 ** 30–40 ND 8 26–28 1 8–34 4 ND ND ND ND 29 ND 87 13–40 70 34–95 † 75 *** ND 34 ††† 73 56–86 *** Page 6 of 8 (page number not for citation purposes)