Vitamin D facts

Vitamin D is the nutrient that has captured the attention of the scientific community, regulatory agencies, the food industry and the public alike over the past 15 years. While there are many controversial issues in relation to vitamin D requirements and the impact of vitamin D intake and status on human health, there is a general agreement that prevention of vitamin D deficiency is a public health priority.

Background of the problem

The major source of vitamin D in humans is sunshine. Several environmental factors, such as latitude and prevailing weather conditions, determine whether sunshine of sufficient strength is available to stimulate the conversion of 7-dehydrocholesterol in the skin to pre-cholecalciferol. Personal attributes, such as skin pigmentation, age, attire, sunscreen, working environment, physical activity and sun exposure behaviour can also prevent or impede vitamin D synthesis.

European context

Vitamin D occurs in the diet, both naturally and as nutritional supplements. Vitamin D intakes are typically low as it occurs naturally in few foods and, when present, is often in low concentrations.

A substantial fraction of the European population, including all who reside at latitudes greater than around 40°N, rely on body stores and dietary vitamin D to maintain a healthy vitamin D status all year round. Given that body stores are dependent on sun exposure, the importance of food in maintaining vitamin D status is a corollary of sunshine deficit. In Europe in particular, there is increasing evidence that the dietary supply is currently unable to offset the seasonal sunshine deficit, which increases with latitude and the duration of winter. While nutritional supplements contribute a high proportion to total vitamin D intake among users, supplement intake is voluntary, and tends to be highest among infants and elderly adults and lowest among children, adolescents and young adults, who are also at risk of deficiency.

A high proportion of European residents are at risk of not maintaining a healthy vitamin D status all year round. The risk is increased in persons who have low habitual sunshine exposure, diminished ability to synthesize or metabolize cholecalciferol, whose food intake is low or who have higher vitamin D requirements. Such risk factors are all relatively common attributes that apply to individuals with dark or ageing skin, those who avoid the sun or comply with sun protection guidance, those who work or attend school indoors during the day, adults on energy-restricted diets or young children whose dietary intake is relatively small and those who may have increased vitamin D requirements due to pregnancy, lactation or growth. In short, the groups at risk of low vitamin D status represent a sizeable majority of the school going and working population in Europe, and include all age, sex and life-stages and both white and dark-skinned persons, regardless of habitual diet and body size.