Vitamin D is a fat-soluble vitamin that plays an important role in bone metabolism and seems to have some anti-inflammatory and immune-modulating properties. For most people sunlight is the most important source of vitamin D. The time required to make sufficient vitamin D varies according to a number of environmental, physical and personal factors, but is typically short and less than the amount of time needed to damage the skin e.g. reddening and burns. Enjoying the sun safely, while taking care not to burn, can help to provide the benefits of vitamin D without unduly raising the risk of skin cancer. Vitamin D supplements and specific foods can aid in maintaining sufficient levels of vitamin D, particularly in people at risk of deficiency. However, there is still a lot of uncertainty around what are “optimal” or “sufficient” levels, how much sunlight different people need to achieve a given level of vitamin D, and whether vitamin D protects against chronic diseases such as cancer, heart disease and diabetes, as well as the benefits and risks of widespread supplementation.