Abstract
Almost one in five adults aged 19–65 years in the UK has a low serum vitamin D concentration (below 25 nmol/l) according to the National Diet and Nutrition Survey (NDNS) (Roberts et al. 2018), which puts them at increased risk of the manifestations of vitamin D deficiency, described below. In some age groups, prevalence is even higher; for example, 39% among adolescent girls aged 11–18 years. Government recommendations in the UK emphasise the importance of ensuring adequate vitamin D for everyone to protect bone and muscle health. Public Health England (PHE) advises that adults and children over the age of 5 years require an average of 10 µg of vitamin D a day and should consider taking a daily supplement during autumn and winter (a combination of diet and sunshine exposure is sufficient for most people during the spring and summer provided they spend time outside). There is also specific advice for the under-fives (Table 1). People who have a higher risk of vitamin D deficiency are being advised to take a supplement all year round (Table 1).