When did you last check your level of vitamin D? Vitamin D (25 OH) Blood Test.

It is estimated that more than 70% of adults are deficient in vitamin D3, the sunshine and bone health vitamin. But this vitamin is essential because it plays a key role in the immune system function, mental balance and the incidence of certain viruses.

What is vitamin D?

Vitamin D is known as the “sunshine vitamin”; however, it’s not strictly a vitamin (it’s a hormone) as it can be synthesised on the skin when the body is exposed to sunlight.

Vitamin D is the general name given to two different compounds – ergocalciferol (vitamin D2) and cholecalciferol (vitamin D3). 

The body creates vitamin D on the skin when exposed to direct sunlight; the ultraviolet B (UVB) rays from the sun stimulates vitamin-D receptor cells in the skin that triggers a chemical reaction in the body, enabling it to produce vitamin D3. Vitamin D can be stored in the liver for four months.

Experts recommend short bursts of unprotected sun exposure (around 5 – 10 minutes), a few times per week for fairer skin types, in order to maintain vitamin D levels. For those with darker skin tones, it can take three to six times longer to produce the same amount of vitamin D3 due to their skin pigmentation.

Why is vitamin D so important?

• The major biological function of vitamin D is to maintain normal blood levels of calcium and phosphorus. Vitamin D aids in the absorption of calcium, helping to form and maintain strong bones. 
• Being a powerful immune modulator, Vitamin D supports immune function and can improve the body’s antimicrobial defence system. It also helps regulate immune cells and reduce inflammation to promote a healthy immune response. Those with allergies, constant infections (viral and bacterial) and autoimmune conditions should get their vitamin D levels checked.
• Vitamin D has shown to have anti-cancer properties and the ability to regulate gene cells, enhancing anti-tumour activity of immune cells. It also inhibits angiogenesis (the formation of new blood vessels for tumour cells), preventing cancer cells from receiving the oxygen and nutrients they need to grow.
• In the gastrointestinal system, vitamin D plays a role in keeping the gut microbiome healthy (by increasing beneficial gut bacteria), protecting the gut barrier and regulating inflammation, especially of the gut lining. 
• Vitamin D is also involved in blood sugar metabolism; it aids the secretion of insulin (the hormone that helps transport glucose into cells) and increases insulin sensitivity in cells. 

Symptoms of a deficiency

Usually, there are no symptoms of a vitamin D deficiency. If they’re present the signs are often subtle, but some people may notice:

• Getting illnesses or infections more often
• Feeling tired or fatigued
• Hair loss
• Muscle pain
• Lower back pain
• Feelings of depression or low mood
• Wounds that heal slowly following surgery, infection or injury

Who’s at risk of low vitamin D?

• People who are not often outdoors
• People who cover a lot of their skin when outdoors
• People with darker skin tones
• People following a plant-based diet, as a lot of foods that naturally have vitamin D are fish, red meat and eggs
• People with an autoimmune condition.

Government advice is that adults should consider taking a vitamin D supplement during the autumn and winter months to protect their bone and muscle health.

What is an optimal serum vitamin D level?

The reference ranges for vitamin D in the UK are as follows:

• Below 25 nmol/L indicates deficiency
• 25 – 50 nmol/L is sub-optimal
• 50 nmol/L and above is considered normal
• 75 – 125 nmol/L is the optimal range for vitamin D

Re-testing blood levels every four months (after supplementation) is recommended so your vitamin D dosage can be adjusted accordingly.

How to increase your Vitamin D levels naturally

• Go for a walk in the sun.
• Increase your intake of organic vegetables which contain important cofactor nutrients and eat more vitamin D containing foods including sun-exposed mushrooms, organic egg yolks and oily fish like sardines and mackerel.