These include a range of illnesses such as flu, pneumonia and bronchitis after previous studies linked vitamin D deficiency to an increased risk of severe Covid - another respiratory infection. The boffins discovered that for every 10 nmol/L increase in vitamin D, the hospital admission rate fell by four per cent. Abi Bournot, lead author of the study from the University of Surrey, said: "Vitamin D is vital to our physical well-being. Despite its importance to our overall health, many people are deficient and do not meet the government's recommended intake of 10 micrograms of vitamin D per day. "Supplementation of the vitamin, especially in the winter months when our exposure to sunlight is limited, is an effective way of increasing vitamin D and reducing the risk of serious respiratory tract infections.