Vitamin D3, often referred to as the 'Sunshine Vitamin', is produced in the body through a chemical reaction that takes places during direct exposure to the sun's UV rays as wel as being present in some foods, such as fortified cereal and orange juice. It is utilised by the body to aid the absorption of Calcium and Phosphorous, and is important for maintaining normal bones, teeth and muscle function.
Throughout the winter, and when you spend a lot of time indoors, we limit our body's natural ability to make Vitamin D from UV light exposure. 
Lifeplan's Vegan Vitamin D3 1000iu supplement was formulated with this in mind; made from Lichen extract and containing 500% of the Nutrient Reference Value (the daily amount needed of a vitamin or mineral that the average healthy person needs to prevent deficiency) of D3. 
Registered with the Vegan Society.