What are the main risk factors for vitamin D deficiency?
Vitamin D deficiency is often related to insufficient exposure to the sun.
Other risk factors are:
– Age: Older people have a reduced ability to synthesize vitamin D in the skin when exposed to UVB radiations (sun) and are more likely to stay indoors or use sunscreen, which prevents vitamin D synthesis (Holick, 2011)
– Skin pigmentation: Melanin reduces vitamin D synthesis. People with darker skin require longer UVB exposure to produce the same amount of vitamin D as those with a lighter skin tone.
– Geographical location and seasons: Geographical location influences vitamin D levels because people living further away from the equator do not get enough sunlight (UVB). In winter and in areas north of the 40th parallel (for people living in the northern hemisphere) the number of photons reaching the Earth’s surface is significantly reduced, and hence reducing vitamin D synthesis.
During the winter period, people living north of the 40th parallel (north of the Madrid-Naples line), are probably not sufficiently exposed to the sun to meet their vitamin D needs.
An American study shows that during the summer and at noon, 3 to 8 minutes of sun for people with slightly tanned skin and exposing 25% of their skin, are sufficient to produce 400 IU of vitamin D in the city of Boston (located at the 42nd parallel). In winter, on the other hand, it is almost impossible for these same persons to synthesize vitamin D. (Terushkin, 2010)
– Lifestyle: Today, most Westerners spend most of their time indoors (house, office, car etc ..) resulting in significant vitamin D deficiencies. This can only be offset by the daily intake of a vitamin D dietary supplement.
– Sun protection: Sun protection such as shade, sun-protective clothing, and the application of sunscreens, hinder the exposure of the skin to the sun’s rays and lead to a decrease in vitamin D synthesis. The application of Sun cream (2 mg/cm2) with a sun protection factor (SPF) of 10 reduces UVB radiation by 90% (Balk, 2011).
CAUTION: The risk of skin cancer increases when people overexpose themselves to the sun and intentionally present themselves to artificial UV sources.
– Overweight and obese people: Vitamin D is fat soluble and is stored in the body fat. Obese and overweight people may thus need two to three times more vitamin D than others.
– Breastfed babies: Daily intake of vitamin D is recommended in breastfed infants. Another alternative is that the mother takes vitamin D supplement to indirectly enrich breast milk.