Vitamin D is essential for the healthy functioning of our bones, teeth, and muscles. This vitamin is mainly secreted due to the sun's rays on the skin. However, while under lockdown, we have all been spending less time outdoors in the sun.A vitamin D deficiency is not without consequences on the health. It can cause bone deformation, called rickets in children. Adults can suffer from a similar condition called osteomalacia. Some studies also suggest that the molecule contributes to our resistance to infections. It is therefore particularly important during an epidemic.Do I need to supplement with vitamin D?In the UK, the Public Health Agency has recommended that people in the UK should take a daily vitamin D supplement throughout the spring and summer, as reported by the BBC. It already recommends that people should take a daily dose of 10 μg per day during the winter months, and all year round if they spend little time outdoors.A 2015 study conducted by French Public Health showed that only one in four adults, and three out of ten children reach an adequate vitamin D threshold. These figures give rise to fears that more people are lacking in this vitamin during this unprecedented period. There are, however, ways to make up for this lack.First of all, adults should not exceed 100 μg per day, and children 50 μg. Although vitamin D supplements are safe, taking more than the recommended amount of 10 μg daily can be dangerous in the long term. People with certain medical conditions, such as kidney problems, should not take it.This is why the French National Food Safety Agency (Anses) does not recommend dietary supplements unless suggested by a health professional. '[Taking them] may cause excessive levels leading to hypercalcaemia [...] with consequences on the heart and kidneys,' it said in a statement.From food to light therapyWhile 80% of our needs are created by UV rays, the rest is provided for by foods that are rich in the molecule: fatty fish, eggs, dark chocolate, mushrooms... Some grains, kinds of margarine, and yoghurts are also enriched with the vitamin. But it is difficult to get enough vitamin D through diet only, although it should be noted that a balanced diet is still essential to ensure the proper functioning of the immune system.As for light therapy lamps, which compensate for the lack of sunshine by regulating our internal clock and sleep cycles, they only mimic the light, and do not diffuse UV rays directly. Therefore, they do not stimulate the body's ability to produce vitamin D. However, if depression linked to a lack of sunlight is particularly noticeable, they are still your best ally for staying in a good mood.Ideally, you should always expose your hands, forearms, and face to the sun for at least 15 to 20 minutes a day. You can do this from your window, as long as it is open since windows filter out UV rays. All of this should of course be done while protecting your skin from the sun.