Vitamin D supplements are not necessary for everyone during the winter months, French physician Dr Jean-Marc Sène told television viewers on Tuesday morning.
Speaking on the TF1 morning programme Bonjour!, Dr Sène warned against the unjustified use of vitamin products and said that people should not assume they require daily tablets simply because cold weather has arrived.
The skin naturally slows its production of vitamin D during winter because of the seasonal lack of ultraviolet B rays from sunlight, Dr Sène explained. Despite that drop in natural synthesis, he alerted viewers that taking dietary supplements without a clear medical need carries risks.
Winter sunlight and vitamin synthesis
Vitamin D plays a vital role in human health by helping the body absorb and regulate calcium and phosphate. These essential minerals keep bones, teeth and muscles strong. A prolonged lack of the nutrient can lead to rickets in children and a softening of the bones known as osteomalacia in adults.
During the spring and summer months, the body manufactures most of its vitamin D through direct sunlight exposure on uncovered skin. In temperate latitudes, however, the sun remains low in the sky throughout autumn and winter. The atmosphere filters out ultraviolet B radiation, leaving sunlight too weak to trigger natural synthesis in the skin.
While sunlight is the primary natural trigger for vitamin production, small amounts are also absorbed through foods. Oily fish such as salmon, mackerel and sardines, as well as red meat, egg yolks and fortified cereals, contribute to maintaining baseline nutritional levels.
Risks of excess supplementation
Health specialists have increasingly warned against the indiscriminate consumption of high-dose over-the-counter supplements. Unlike water-soluble vitamins, which the body flushes out in urine when consumed in excess, vitamin D is fat-soluble and accumulates in body tissues over time.
Excessive consumption over extended periods can trigger hypercalcaemia, a condition marked by abnormally high calcium levels in the bloodstream. The buildup can weaken bone structure, promote kidney stone formation, and cause damage to the kidneys and heart.
Dr Sène addressed the issue during the regular Allo le doc segment of Bonjour!, the flagship morning news broadcast operated by French commercial television network TF1. The network published the segment through its TF1info digital video service on 3 November 2026.
