Winter is not kind to our energy. Gray skies, short days, the need to wear coats… Everything comes together to deprive the skin of the sun and therefore of vitamin D. However, 70% of this essential hormone is produced naturally by skin exposure to UVB rays. Result: the body slows down, as does morale.
What is the role of vitamin D?
Vitamin D acts as a real internal regulator. It supports the immune system, strengthens bones and plays a role in serotonin, this well-being molecule.
Without it, the “winter blues” come rushing back, which is why we feel less energetic during this season.
How long should you be exposed to produce enough vitamin D?
According to a Spanish study, it takes about two hours of exposure in January, around midday, to reach the recommended daily dose.
No need to tan or go naked: face, neck, hands and forearms are enough. The only condition: that they be directly exposed to light.
For comparison, seven minutes is enough in July and thirty minutes in October. Further proof that winter light, softer but rarer, requires a little more discipline.
Dr. Gérald Kierzek, emergency physician, completes these recommendations.
“Vitamin D is essential, especially in winter, where the lack of sunlight limits its production by the skin via UVB rays. Good exposure to the sun, even limited to 15 to 30 minutes per day on the face and arms during the rare fine winter days, ensures sufficient synthesis for most people.”
Fatigue, pain, low morale: the signs of vitamin D deficiency
But how do you know if you are deficient in vitamin D? Dr. Kierzek says that if in doubt, a simple blood test for 25-hydroxyvitamin D can detect a deficiency. Indeed, very often, a vitamin D deficiency will manifest itself in an insidious manner.
Persistent fatigue, loss of tone, muscle or bone pain, or even increased vulnerability to infections are warning signals. In the long term, lack of vitamin D can increase the risk of fractures, osteoporosis and immune system disorders.
Supplements: be careful of overdose
If a deficiency is proven, vitamin D3 supplementation is recommended, under medical supervision. Doses vary depending on the profile: often between 800 and 2000 IU per day for adults at risk. Dr. Kierzek recalls that this vitamin “promotes the absorption of calcium and phosphorus, strengthens bones and teeth, and also supports the immune system“.
But beware of excess too. Vitamin D accumulates in the body and too high an intake can cause hypercalcemia, that is, excess calcium in the blood.
“An overdose will manifest as nausea, headache, muscle or heart pain, and can lead to calcium deposits in the kidneys, heart or blood vessels.” lists our expert. However, these serious effects generally appear as soon as the intake exceeds 50,000 IU per day, well beyond the commonly prescribed doses.
Finally, Dr. Kierzek reminds that people undergoing treatment for heart rhythm disorders should avoid vitamin D supplements.In all cases, any intake greater than 2,000 IU per day must be strictly supervised by a health professional. he concludes.