When we talk about vitamin D, the first thing that comes to mind is the health of our bones, and how important it is for the prevention of skeletal diseases, because it stimulates calcium absorption and deposits of this mineral in bone tissue. So an adequate amount is to be recommended right from an early age, to prevent rickets, typical in childhood, and osteoporosis in adulthood.
But vitamin D is much more important than we realise. Its active form, calcitriol or 1 25-dihydroxycholecalciferol, behaves more like a hormone, in that it is able to regulate various metabolisms and interact with more than 1000 genes involved in the development of the nervous and immune systems, the reason for which good levels of calcitriol have been linked to a lower risk of heart attack, Alzheimer’s, inflammatory diseases, auto-immune and thyroid illnesses, and cancers. And yet hypovitaminosis D is common the world over today, particularly among pregnant women.
But how do we consume vitamin D? Although contained in some foods (cod liver oil, mackerel, anchovies, sardines, egg yolk, butter), our food only accounts for roughly 10-20% of our daily vitamin D intake, the remaining 80% resulting from sun exposure. When UVB sun rays hit the skin (the dermis), they activate a vitamin D precursor, which is then transformed into the active vitamin in our body.
Although Italy is a country that enjoys sunny weather for a good part of the year, hypovitaminosis D is still fairly common and one of the main causes appears to be significant environmental pollution and the greenhouse effect which reduce the effectiveness of the sun’s rays.
In terms of specific causes, those most at risk include people who have reduced skin synthesis capacity because they rarely sunbathe, those with dark skin, those who use a lot of protective sun creams, the elderly, the obese, the sedentary, coeliacs, vegans or those needing greater doses, such as pregnant and menopausal women. How can we identify a vitamin D deficiency? Alarm bells can include muscular complaints, such as weakness, spasms, cramps and pins and needles, as well as skeletal deformities and swelling of the joints. How can we know our vitamin D levels and correct them? In Italy, the best time to receive a dose of vitamin D into the blood is October, after the summer. A value of less than 30 ng/ ml indicates hypovitaminosis, while less than 20 ng/ml means a deficiency, for which the doctor will prescribe a supplement, which should only be taken in these cases. To prevent this, regular sun exposure is key, the period of time dependent on skin colour. 20 minutes is recommended for fair skin, 30 minutes for normal skin and 45 minutes without sun protection for very dark skin. Eating foods rich in magnesium, zinc and vitamin K (vegetables and nuts) improves the efficiency of vitamin D synthesis, as does physical exercise, which should never be overlooked!