Vitamin D is often called the 'sunshine vitamin' because our skin makes it when exposed to sunlight. Here we explain what it does, where to find it and what UK guidance recommends.
What vitamin D does
Vitamin D contributes to:
- the normal absorption and utilisation of calcium and phosphorus;
- normal blood calcium levels;
- the maintenance of normal bones and teeth;
- the maintenance of normal muscle function;
- the normal function of the immune system;
- the process of cell division.
Vitamin D is also needed for normal growth and development of bone in children.
Two forms of vitamin D
- Vitamin D2 (ergocalciferol) – found in plant and fungi sources, such as mushrooms exposed to UV light.
- Vitamin D3 (cholecalciferol) – made in the skin from sunlight and found in foods of animal origin.
Both forms need to be converted by the liver and kidneys to become active.
Foods that contain vitamin D
Very few foods are naturally rich in vitamin D: oily fish (salmon, mackerel, sardines, tuna), eggs, fortified foods and UV-exposed mushrooms. Mushrooms naturally contain ergosterol, which converts to vitamin D2 when they are exposed to UV light – for example, Shiitake dried in sunlight contains more vitamin D than Shiitake grown indoors. A 2018 review in Nutrients found that UV-exposed mushrooms can raise blood vitamin D levels.
Sunlight
Most of our vitamin D comes from sunlight. Short periods of midday sun on the face and arms in spring and summer can help, but take care not to burn – and remember that cloud, latitude and time of year all affect how much vitamin D the skin makes.
UK guidance
In the UK, from April to September most people can make enough vitamin D from sunlight on their skin. From October to March, public health guidance recommends that everyone considers a daily supplement of 10 µg (400 IU). Some groups – such as people who rarely go outdoors or who have dark skin – should consider a supplement all year round. Do not exceed 100 µg (4,000 IU) a day unless advised by a doctor.
Signs of low vitamin D
Very low vitamin D levels can affect bones and muscles. If you are concerned, speak to your GP, who can arrange a blood test.
CocoVit D+K2
Our CocoVit D+K2 drops combine vitamin D3 with vitamin K2 in coconut MCT oil. Vitamin D contributes to the normal function of the immune system and the maintenance of normal bones; vitamin K contributes to the maintenance of normal bones.
Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle.