Vitamin D3 (cholecalciferol) is one of the most popular food supplements – and for good reason: many people in the UK have low vitamin D levels, especially in winter.
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.
How the body makes vitamin D
- UVB rays from the sun convert a compound in the skin (7-dehydrocholesterol) into pre-vitamin D3.
- In the liver, it is converted to 25-hydroxyvitamin D, the form measured in blood tests.
- In the kidneys, it becomes the active form, 1,25-dihydroxyvitamin D.
Food sources
Few foods are naturally rich in vitamin D:
- Oily fish – salmon, mackerel, sardines, trout (vitamin D3).
- Eggs – mainly the yolk (vitamin D3).
- Fortified foods – some breakfast cereals, spreads and plant-based drinks.
- UV-exposed mushrooms – contain vitamin D2; mushrooms naturally contain ergosterol, a precursor that converts to vitamin D2 under UV light.
Vitamin D3 or D2?
Both forms are converted in the liver and kidneys. Research suggests vitamin D3 may be more effective at raising and maintaining blood levels.
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.
CocoVit D+K2
Our CocoVit D+K2 drops combine vitamin D3 with vitamin K2 in coconut MCT oil. Vitamin K contributes to the maintenance of normal bones. Follow the recommended daily intake on the label.
A little history
Herodotus reported a curious observation from ancient Egypt: Egyptian skulls, exposed to the sun from childhood, were stronger than Persian skulls covered by turbans. In 1919 Sir Edward Mellanby linked a dietary factor to rickets, and in the 1930s Adolf Windaus helped determine the chemical structure of vitamin D3.
Food supplements should not be used as a substitute for a varied, balanced diet and a healthy lifestyle.