Hypovitaminosis D: a major worldwide public health issue

Physiology: Vitamin D increases intestinal absorption of calcium favoring t he microenvironment necessary for bone mineralization. in addition, vitamin D prevents hypocalcemia via its osteoclastic action. Severe hypovitaminosi s leads to rickets in children and its equivalent in adults, osteomalacia. Mild to moderate hypovitaminosis D causes secondary hyperparathyroidism inc reasing the risk of fracture, particularly femoral neck fracture. Vitamin D would also have an antiinflammatory and anticancer effect. Worldwide: Hypovitaminosis D is frequently observed in Europe in the elderl y, particularly in the institutionalized population, but is also seen in ot herwise healthy younger adults. An estimated 40% of the young European popu lation has some degree of hypovitaminosis D. Surprisingly, it is more frequ ent in sunny Mediterranean countries than in certain northern countries suc h as Norway. The lower incidence observed in the United States is probably related to the vitamin D supplementation of the American diet. Hypovitamino sis D in Africa and the Middle-East is also an important problem, being con sidered to be one of the 5 most prevalent childhood diseases in developing countries. Environmental factors: The limited quantity of vitamin D in food and multip le environmental factors contribute to hypovitaminosis D. These factors inc lude insufficient sun exposure and urban lifestyle with a high degree of po llution. In addition, cutaneous photosynthesis of vitamin D is limited by h yperpigmentation in black people, wearing traditional veils that limit sun exposure, and use of sun lotions, further contributing to vitamin D deficie ncy. Conclusions and recommendations: The very high prevalence of hypovitaminosi s D in the world, and particularly in Europe, Africa and the Middle-East, p oints to the need for public health measures in these countries. While wait ing for these measures to be implemented, vitamin D supplementation (for ex ample in tablet form) should be encouraged in order to meet minimum require ments. Finally, the beneficial effect of moderate sun exposure on cutaneous vitamin D synthesis land psychological well-being must not be overlooked.