Vitamin D is well known as the ‘sunshine vitamin’.
It is a fat-soluble vitamin that functions like a steroid hormone in the body and is responsible for many important functions such as:
Immunity which plays an important role in our ability to fight infections
Hormonal health by balancing our sex hormones
Supporting a healthy digestive system
Bone health, as vitamin D regulates the amount of calcium and phosphate in the body, both needed for healthy bones, teeth and muscle (1)
Improving brain development and function
We can get vitamin D by:
Spending time outdoors in the sunlight. When it is exposed to UVB rays from sunlight the body converts cholesterol in the skin into an active form of Vitamin D (3)
The vitamin D we make from the sunshine or that we get from certain foods is sent to the liver where it is converted into the active form calcidiol 25(OH)D which is the storage form of vitamin D in the body.
There are two types of vitamin D. Vitamin D2 (ergocalciferol) from plant sources, i.e. mushrooms, and vitamin D3 (cholecalciferol) from animal sources such as oily fish and egg yolks as well as the supplemental forms. Vitamin D3 is the more powerful of the two types as it is bioavailable and raises blood levels of vitamin D almost twice as much as D2 (4)
From about April to the end of September, most people should be able to get all the vitamin D they need from sunlight but it also depends on your skin colour, as dark skin produces less vitamin D (5)
However, during the winter months in the UK, we don’t get enough vitamin D from the sunlight even if we get outside every day because sunlight is limited and the sun’s rays are too weak. Therefore, most people in the UK are at risk of vitamin D deficiency (6)
The Scientific Advisory Committee on Nutrition (SACN) published a recent survey which found that 1 in 5 people have low vitamin D levels and this can be a real problem during the winter especially when it extends over long months (7)
I recommend that you see a GP or Nutritionist before you prescribe yourself with supplements. They will provide a blood test to find out your vitamin D levels. Blood levels of vitamin D are assessed by measuring 25(OH)D - 25-hydroxy vitamin D in the blood (8)
The correct dosage of supplemental vitamin D and supplemental form can then be given.
It is advised to supplement during the winter months. ‘PHE advises that in spring and summer, the majority of the population get enough vitamin D through sunlight on the skin and a healthy, balanced diet. During autumn and winter, everyone will need to rely on dietary sources of vitamin D. Since it is difficult for people to meet the 10 microgram recommendation from consuming foods naturally containing or fortified with vitamin D, people should consider taking a daily supplement containing 10 micrograms of vitamin D in autumn and winter’ (9)
It is possible to get too much vitamin D/overdose from supplements (or cod liver oil) which can cause Hypercalcemia (abnormally high calcium level in your blood). Signs include nausea and vomiting. (However, it is almost impossible to get too much vitamin D from sunlight or from foods alone).