Vitamin D is a crucial nutrient for the human body, as highlighted by the French National Agency for Food, Environmental and Occupational Health Safety (Anses). It plays a key role in regulating calcium and phosphorus levels in the blood, which are essential for strong bones, muscle function, nerve communication, and blood clotting. One of the primary ways the body obtains vitamin D is through exposure to sunlight. Spending 15 to 20 minutes in the sun during the late morning or afternoon allows the skin to produce enough of this vitamin. In addition to sunlight, certain foods are rich in vitamin D. These include cod liver oil, fish eggs, fatty fish like herring, sardines, salmon, anchovies, and mackerel, as well as fortified foods such as cereals, dairy products, egg yolks, and specific mushrooms like morels, porcini, and boletus. Despite the importance of vitamin D, some people take supplements to prevent health issues like fractures and falls, particularly as they age. However, a major study involving over 153,000 adults found that calcium and vitamin D supplements, whether taken separately or together, are not very effective in reducing the risk of fractures or falls in older individuals. The findings, published in the BMJ journal, suggest that these supplements provide only minimal or no protection against such injuries. The study, conducted by Canadian researchers, reviewed 69 randomized trials involving 153,902 adults. These trials compared the effects of calcium, vitamin D, or both with a placebo or no treatment, focusing on whether they could reduce the likelihood of fractures or falls. The researchers established specific thresholds to measure the impact of the supplements and found little to no effect on the risk of fractures. According to the study’s authors, calcium, vitamin D, and combined supplements "appeared to have little or no effect," with most of the evidence classified as having a moderate to high level of certainty. Based on these results, the researchers concluded that the data "do not justify systematic calcium or vitamin D supplementation, or combined supplementation, to prevent fractures and falls." This challenges the common belief that these supplements are effective for bone health in older adults. The study highlights the need for further research and a more nuanced understanding of how nutrients like calcium and vitamin D affect different populations. While the findings do not dismiss the importance of these nutrients entirely, they suggest that relying solely on supplements may not be the best strategy for preventing fractures and falls. Instead, a balanced approach that includes a nutritious diet, regular physical activity, and adequate sunlight exposure may be more beneficial for maintaining bone health in older adults.