Vitamin D deficiency is not always linked to insufficient exposure to sunlight. Other causes need to be explored, especially in women.
A lack of exposure to the sun
“Vitamin D is produced in 70% through the skin under the effect of ultraviolet rays from the sun. The remaining 30% is provided by food, immediately explains Florence Foucaut, dietician-nutritionist and member of the French Association of Dietitians-Nutritionists. Most often, the lack of vitamin D is caused by insufficient exposure to sunlight. “In winter, we lack sunshine. The light is weaker and short-lived compared to the spring/summer season. Furthermore, in winter, we are more covered; therefore, we are less exposed and the synthesis of vitamin D is less good. Conversely, exposing your forearms in the summer, for a few minutes a day, is enough to build it. Furthermore, vitamin D can be stored. It is therefore possible to exhibit in summer (except from 12 p.m. to 4 p.m.) to increase our stock, which will slowly deplete during the winter“.
Low consumption of fatty fish
About a third of vitamin D is provided through food. By consuming certain rich foods, combined with sufficient exposure to daylight, daily requirements can be met. Globally, a deficiency can occur in the absence of consumption of foods source of vitamin D as fatty fish (sardines, salmon, mackerel, etc.)dairy products (especially those enriched with calcium and vitamin D), cod liver, certain mushrooms, egg yolk, offal (particularly meat liver).
Dark skin promotes deficiencies
They have a large quantity of melanin which can block UV rays.
“People with olive and dark skin are at greater risk of vitamin D deficiency, indicates our nutritionist. Indeed, they have a large quantity of melanin, skin pigment that can block UV and in fact the synthesis of vitamin D. On medical advice, they may be advised to supplement during the winter period..” Moreover, among people who use the total screen excessivelythe synthesis is less efficient.
A hormonal change
“THE hormonal upheavals have an impact on vitamin D biosynthesis. Pregnant women and postmenopausal women are therefore populations at risk of deficiency“, explains our interlocutor. Hormonal fluctuations can cause bone demineralization, which increases the risk of fracture.
Overweight and obesity
“Vitamin D is fat soluble, so it is stored in adipose tissue. Being overweight or obese can potentially cause a lack of bioavailability of vitamin D“, she explains. Certain pathologies are also at risk, notably those which induce intestinal malabsorption, such as celiac disease (gluten intolerance) or following bariatric surgery.
A vegan diet
Diets eliminating meat, fish, eggs or dairy products promote the risks of vitamin D deficiency. Florence Foucaut recommendse consult for prevention a food professional, a dietician-nutritionist, or even their pharmacist, particularly for adult populations at risk of deficiency.
Age, a proven risk factor
Infants and the elderly are particularly at risk of vitamin D deficiency.”As we age, our skin synthesizes less vitamin D. The skin of older people is very thin. Therefore, less vitamin D is made“, explains Florence Foucaut. A lack of this vitamin in the elderly promotes the occurrence of osteoporosis and the risk of femoral neck fracture. To ensure the proper growth of their skeleton and prevent rickets, newborns are systematically supplemented in France on medical prescription. “Infants born from September are more concerned, linked to insufficient exposure to natural light, essential for the synthesis of vitamin D. In autumn and winter, babies are covered, well bundled up, and practically no skin area is exposed,” describes our expert. Babies born in summer, for their part, can have their arms uncovered during a walk, without exposing them to the sun of course (it is rather recommended to avoid walking your baby between 12:00 p.m. and 4:00 p.m. when it’s hot outside).
Thanks to Florence Foucaut, dietician-nutritionist and member of the AFDN (French Association of Dietician Nutritionists).