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All about vitamin D

Although referred to as a vitamin, vitamin D has the chemical structure of a hormone and has a role in numerous functions within the body. Most commonly associated with bone health, it is now known that there are vitamin D receptors in most of our organ and research suggest that deficiency is a contributory factor in many chronic decreases.

Vitamin D is produced in the body when the skin is exposed to sunlight, only a small amount comes from food.  The use of sunblock during summer, which prevents synthesis of vitamin D, coupled with the lack of sunshine during the winter months can result in a deficiency. Groups that are at higher risk of deficiency include babies & children under 5, adults over 65, people who are housebound with very little sun exposure and people with darker skin. Vitamin D requirements are also higher in pregnant or breastfeeding women.

Functions of vitamin D

Calcium regulation - Vitamin D is essential for the absorption of calcium and low levels are linked to increased risk of osteoporosis. It also helps to keep blood levels of calcium within the narrow range required for normal functioning of the nervous system.

Immune regulation – Enhances innate immunity, helping to protect against infection, and also inhibits autoimmunity, associated with a lower risk of developing autoimmune conditions such as rheumatoid arthritis and multiple sclerosis.

Brain function – Research suggests vitamin D deficiency has a role in seasonal affective disorder  (SAD) and other mood disturbances, and Alzheimer’s disease. It is also vital for foetal brain development which is why pregnant and breast feeding women are advised to take a supplement.

Cell differention - By controlling the rate at which cells growth and multiply, it is thought that vitamin D may help to protect against some forms of cancer.

Cardiovascular health - Low levels of vitamin D have been associated with hypertension, and risk or heart attack and stroke.

If you are concerned about vitamin D deficiency contact your GP or nutritionist to arrange a blood test.

Food sources of vitamin D

Oily fish (salmon, mackerel, sardines, pilchards), eggs, mushrooms and fortified products.


Vitamin D supplements come in two forms; D2 (ergocalciferol) and D3 (cholecalciferol). D3 is the most natural form and considered to be more bioavailable than D2.