Vitamin D status and nutrition in Europe and Asia

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Abstract

Vitamin D status is highly different in various countries of Europe, the Middle East and Asia. For this review, vitamin D deficiency is defined as serum 25-hydroxyvitamin D (25(OH)D) <25 nmol/l. Within European countries, serum 25(OH)D is <25 nmol/l in 2–30% of adults, increasing in the elderly and institutionalized to more than 80% in some studies. A north-south gradient was observed for serum 25(OH)D in the Euronut and MORE studies with higher levels in Scandinavia and lower levels in Italy and Spain and some Eastern European countries. This points to other determinants than sunshine, e.g. nutrition, food fortification and supplement use. Mean vitamin D intake in Scandinavia is 200–400 IU/d, twice that in other European countries. Very low serum 25(OH)D levels have been reported in the Middle East, e.g. Turkey, Lebanon, Jordan and Iran. In these countries serum 25(OH)D was lower in women than in men and associated with clothing habits. In a Lebanese survey, vitamin D deficiency was observed in the majority and occurred mainly in veiled women. In India, vitamin D deficiency was observed in more than 30%, vitamin D status being poor in school children, pregnant women and large cities. Vitamin D status was much better in Malaysia and Singapore, but lower serum 25(OH)D was observed in Japan and China. Rickets and osteomalacia appear quite common in India, but precise data are lacking. Immigrants in Europe from the Middle East and Asia carry a high risk for vitamin D deficiency, pregnant women being especially at risk. Comparison of vitamin D status between countries is hampered by interlaboratory variation of serum 25(OH)D measurement. In addition, there is a need of population-based data. In conclusion, vitamin D deficiency is common in Southern Europe, the Middle East, India, China and Japan. It is less common in Northern Europe and Southeast Asia. Risk groups are young children, the elderly, pregnant women and non-western immigrants in Europe. Important determinants are skin type, sex, clothing, nutrition, food fortification, supplement use, BMI and degree of urbanization.

Introduction

Vitamin D status is highly different between various countries in Europe, the middle East and Asia [1], [2], [3]. This is caused by different exposure to sunshine, dietary intake of vitamin D and the use of supplements. Vitamin D status is defined according to the serum concentration of 25-hydroxyvitamin D (25(OH)D). For this review, vitamin D deficiency is defined when serum 25(OH)D is lower than 25 nmol/l (10 ng/ml) and vitamin D insufficiency is considered to exist when serum 25(OH)D is between 25 and 50 nmol/l (10–20 ng/ml), as was suggested previously [2]. Vitamin D deficiency causes secondary hyperparathyroidism, bone resorption and osteoporosis and may contribute to fractures [2]. Severe vitamin D deficiency (serum 25(OH)D < 12.5 nmol/l or 5 ng/ml) causes mineralization defects, rickets in children and osteomalacia in adults. In more recent years, vitamin D deficiency and insufficiency have been associated with loss of muscle mass [4], muscle weakness measured as slower walking speed and difficulty with standing up from a chair [5] and falls [6]. This review focuses on vitamin D status, vitamin D intake and the prevalence of vitamin D deficiency and insufficiency throughout Europe, the Middle East and Asia. The determinants such as sunshine exposure, dietary intake and use of supplements are also discussed.

Vitamin D status varies highly between different countries in Europe and with aging [1]. The prevalence of vitamin D deficiency varies from 2 to 30% in adults but increases to 80% in institutionalized elderly [2]. In Norway and Sweden the prevalence of vitamin D deficiency is rather low [3], [7], [8]. In Finland, vitamin D deficiency was observed in winter in 26% of women and 28% of adult men [9]. Serum 25(OH)D was somewhat lower in the UK [10], but very low serum 25(OH)D was observed in older women in Ireland [11]. In the Longitudinal Aging Study Amsterdam, a population study in the Netherlands in persons of 65 years and older, vitamin D deficiency was observed in 9.6% (men 8%, women 14.4%). Serum 25(OH)D was lower than 50 nmol/l in 44.7% of the men and 56.1% of the women [4], [12]. Vitamin D intake in older persons in the Netherlands was 114 ± 44 IU/day [13]. A population-based study in Germany in people between 50 and 81 years showed a mean serum 25(OH)D ± S.D. of 50 ± 25 nmol/l and a prevalence of vitamin D deficiency of 25% [14]. The SUVIMAX study in France, a population based study in 765 men and 804 women between 35 and 65 years showed serum 25(OH)D levels varying from 43 ± 21 in the north to 94 ± 38 nmol/l in the south west (latitude from 51° to 43°). In this study serum 25(OH)D correlated positively with sunshine exposure, and negatively with latitude, as expected. The mean dietary vitamin D intake was 160 IU/day in men and 112 IU/day in women [15]. Serum 25(OH)D was lower (43 ± 25 nmol/l) in older French women (80 years) in the EPIDOS study [16]. Studies done in postmenopausal women in Italy showed mean serum 25(OH)D of 45 ± 20 and 46 ± 29 nmol/l, rather unexpectedly, and prevalences of vitamin D deficiency of 28 and 32% [17], [18]. A study in older persons in a home for the elderly in Spain showed a mean serum 25(OH)D of 37 nmol/l, while the mean was 10 nmol/l in geriatric patients [19]. A study in Greece in breast-fed infants showed very low serum 25(OH)D levels, around 25 nmol/l at 3 months [20]. Their mothers had a mean serum 25(OH)D varying from 27 nmol/l in winter to 32 nmol/l in summer. They were not taking any supplements. In adolescent children (15–18 years) in Greece, the prevalence of vitamin D deficiency was 47% in winter, while the prevalence was less (14%) at younger age [21]. Whereas these studies suggest that vitamin D deficiency is more common in southern Europe than in Scandinavia, the interlaboratory variation of 25(OH)D measurement [22] makes these studies difficult to compare. The Euronut study, a European Study based on a population sample of elderly people with a central laboratory facility [23] showed a positive relationship between serum 25(OH)D and northern latitude, i.e. higher levels were found in northern countries than in Southern Europe (Fig. 1). The baseline data of the MORE study, an intervention study in postmenopausal women with osteoporosis, confirmed this observation (Fig. 2) [3]. It may be explained by the common use of cod liver oil and vitamin supplements in Northern European countries, up to 396 IU/day in Norway [24], while people in southern Europe have a more pigmented skin with less vitamin D production and may prefer shadow instead of sunshine.

Vitamin D status, vitamin D intake and prevalence of vitamin D deficiency (serum 25(OH)D < 25 nmol/l) in different studies are presented in Table 1[25], [26], [27], [28], [29], [30], [31], [32], [33]. The latitude of these countries varies between 42° (Turkey) and 18° (Saudi Arabia). While sunshine exposure in these countries is potentially high, vitamin D status varies between poor [30] and good [26]. Vitamin D status showed a strong relationship with life style, especially clothing. Vitamin D status was much better in women with western style clothing than in women with traditional veil with face and hands uncovered (hijab) or covered (niqab) as was apparent in studies from Turkey [25], Jordan [29] and Lebanon [27]. A seasonal variation in serum 25(OH)D was not observed in women wearing a niqab (covering of face) in Jordan [29]. Vitamin D deficiency was particularly prevalent in veiled women in Turkey, Lebanon, Jordan, Saudi Arabia and Iran [25], [27], [29], [32]. In general, serum 25(OH)D was lower in women than in men, and lower in urban than in rural areas [27]. Vitamin D intake in the Middle East was in general 100 IU/day or below, as far as known.

Vitamin D status, vitamin D intake and prevalence of vitamin D deficiency (serum 25(OH)D < 25 nmol/l) in different Asian countries are presented in Table 2[34], [35], [36], [37], [38], [39], [40], [41], [42], [43], [44]. Vitamin D status clearly related to latitude and was poor in the elderly in the eastern Ural in Russia [34], and in Mongolia [35]. The climate in these countries is characterized by short summers and harsh winters. Rickets appears to be common in Mongolia and China [35], and this is probably due to poor vitamin D status and low calcium intake. Several surveys in India showed poor to moderate vitamin D status, unexpectedly low for the latitude, so close to the equator [36], [37], [38], [39]. A reason might be skin pigmentation. In addition, vitamin D intake is very low in India as well as calcium intake. Endemic rickets has been associated with vitamin D deficiency, low calcium intake and fluorosis [45]. Air pollution probably also plays a role in the large cities [46]. Vitamin D status is better in Malaysia [41] and Japan [42], [43], [44]. In Japan, serum 25(OH)D was positively related to fish consumption [44].

Vitamin D deficiency is particularly prevalent among immigrants from the Middle East and Asia in the United Kingdom and has been associated with musculoskeletal pain [47], [48]. Other reports of vitamin D deficiency have come from Norway, where vitamin D deficiency was seen in Pakistani and other Asian immigrants [49], [50]. In Norway a positive relationship was observed between vitamin D status and the consumption of fatty fish and cod liver oil in immigrants [50]. Observations in the Netherlands indicated that generalized musculoskeletal pain in immigrants led to many diagnostic tests, but the diagnosis of vitamin D deficiency was often delayed [51], [52]. Treatment with vitamin D of vitamin D deficient immigrants in Denmark led to an increase of muscle strength [53]. Vitamin D deficiency is particularly common among immigrant pregnant women as was observed in a recent survey in midwife practices in the Netherlands [54].

Vitamin D status is dependent on sunshine exposure and dietary vitamin D intake [13]. The effect of sunshine is modified by skin pigmentation being higher in Southern Europe or India than in Scandinavia or Japan. As was observed in studies in Middle East, skin covering by clothes plays a predominant role in determining vitamin D status [27], [29], [30]. This may also explain why vitamin D status is usually better in men than in women, but this was also the case in the Longitudinal Aging Study Amsterdam [12]. Urbanization and air pollution may also negatively influence vitamin D status [46]. The older skin produces less vitamin D than the skin in younger persons [55], causing susceptibility to vitamin D deficiency in the elderly [2], [56]. Vitamin D content of the diet usually is low, around 100 IU/day or less. Vitamin D intake was lower in Asia than in European countries which may also be caused by fortification of margarine in Europe (usually with 3 IU/gram). The positive effect of fish consumption on serum 25(OH)D has been observed in Norway [50]), the Netherlands [13] and Japan [44]. The use of vitamin D supplements and cod liver oil is common in Northern European countries and has a strong positive influence on vitamin D status. Food fortification except margarine, is uncommon in Europe. Fortification of milk is now practised in Sweden. Body mass index has a negative influence on vitamin D status [12], which is not fully explained. Food fortification can improve vitamin D status in general [57], and the use of vitamin D supplements should be stimulated in risk groups, e.g. breast-fed children [20], pregnant women [35], [37], [54], veiled women [25], [29] and older persons.

Section snippets

Conclusion

Vitamin D deficiency is common in southern Europe, in the Middle East and in many Asian countries. It is caused by low sunshine exposure, skin pigmentation, air pollution, skin covering and low vitamin D intake. The effects are aggravated by low calcium intake. Risk groups include breast-fed children, pregnant women, veiled women and older persons. Vitamin D status can be improved by encouraging sunshine exposure, improving dietary intake, e.g. by fish and cod liver oil, food fortification and

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