The Importance of Vitamin D

Vitamin D can be thought of like the MVP; you will find teeny receptors in the brain, skeletal muscle, our immune cells, and more! When it plays such wide-ranging roles throughout the body, it’s easy to see why most of us are recommended to supplement Vitamin D on a daily basis and why deficiency has been associated with depression to increased severity of respiratory infection!

Let’s take a look at this Vitamin in a little more detail, and the role it plays in the body.


What is Vitamin D? 

Despite its name, Vitamin D is actually a hormone, mostly known for its role in calcium absorption.  You will likely have heard it referenced as the sunshine vitamin as it’s produced in the skin in response to sunlight (UV) exposure.  

There are two forms of Vitamin D.

Vitamin D2 is also known as ergocalciferol which occurs in plants.

Vitamin D3, known as cholecalciferol, is created in the skin during exposure to UV light and occurs in animals.  Cholecalciferol (D3) is of greatest nutritional importance and luckily it can be obtained from the consumption of animal products that contain it. It is defined as a fat-soluble vitamin, which means it can be stored in the body’s fatty tissue.  

importance of vitamin d

Vitamin D and Bone Health

A commonly unknown fact is that Vitamin D plays an indirect role in bone health by managing calcium levels in the body.  Calcium is that trusty mineral that well, is key to bone mineralisation.  Without calcium, bones are unable to form properly.  Bone starts off as soft tissue, when calcium and phosphorus are deposited, it hardens to create the skeletal structure that keeps us strong and upright!

We know Vitamin D plays a role here as in studies of hip fractures, there appears to be a seasonal variation; more occur during winter months and fracture patients often have low vitamin D status.  When supplemented with Vitamin D and calcium, incidences of fractures often reduce. (i)

So, when there is adequate vitamin D, calcium levels are usually maintained and subsequently, bone health is optimised.


Vitamin D and Immune Function 

We find Vitamin D receptors on a range of immune cells, meaning we need sufficient levels of it for them to do their job.  In addition, we know that low levels of Vitamin D are linked with cases of autoimmunity and increased risk of infection with the common cold and more!

When supplemented, Vitamin D has been seen to reduce the incidence of influenza infection.

Vitamin D can help modulate inflammatory responses and is also required for the production of natural killer cells which are known for killing virally infective cells. (i)


There is growing evidence that Vitamin D deficiency could be a contributing factor in the development of both type 1 and 2 diabetes.  It is thought that cells found in the pancreas that secrete insulin contain vitamin D receptors.  Studies have also shown that when treated with a therapeutic dose, vitamin D improves glucose tolerance and insulin resistance. (i)

Cognitive Function

Many studies are establishing a link between low vitamin D levels and cognitive decline.  Vitamin D receptors are widespread in brain tissue and it has a role in cell growth, the production of new neurons, neuroprotection, detoxification, and reduction of inflammation.  Studies have also shown that low vitamin D levels in early life can affect brain development. (i)

Low vitamin D status is often implicated in:

👉 Dementia

👉 Alzheimer’s Disease

👉 Schizophrenia

In addition, in studies involving depression and anxiety, supplementation with Vitamin D has often improved symptoms. (i)  

importance of vitamin d

Vitamin D and Muscle Health 

In some studies, Vitamin D supplementation has been shown to increase muscle strength, particularly in those who are deficient.  Adequate levels of Vitamin D are associated with reduced injury rates and improved sports performance.  (i)

Cardiovascular Disease

Low levels of Vitamin D have been associated with a higher risk of myocardial infarction (heart attack).  The vitamin D axis affects vascular muscle cell proliferation (remodelling or regeneration of cells), vascular calcifications (mineral deposits in arteries and veins), inflammation and blood pressure.   

Causes of Vitamin D Deficiency 

It goes without saying that our diet can result in below optimal vitamin D levels, but there are other factors which can contribute to low levels.  Even if we think we are eating all the vitamin D containing foods, certain health issues can result in malabsorption.

👉 Inflammatory bowel disorders,

👉 Pancreatic insufficiency,

👉 Obesity – being overweight is associated with low vitamin D levels, 

And of course, in our office-based lives, lack of exposure to natural sunlight will deplete our levels too, remember it is known as the sunshine vitamin.  

Signs of Deficiency:

  • Regularly getting ill
  • Fatigue and tiredness
  • Bone and back pain
  • Depression
  • Impaired wound healing
  • Bone loss 
  • Hair loss 
  • Muscle pain

How Much Is Enough?

Recent data highlights that 1 in 5 people in the UK have low vitamin D levels, and so in April 2020 Public Health England updated its long-standing advice that everyone should supplement with 10 micrograms daily.  

This is advised year-round, but even more important in the winter, when we have reduced sunlight exposure.  

Vitamin D is present in a number of foods, like oily fish, red meat, liver, eggs and fortified foods, but it’s often difficult to get enough from diet alone.  

We always advocate a diet first approach but acknowledge that we all need a helping hand every now and again, so if you would like to add a Vitamin D supplement to you daily routine, head on over to our SHOP.

If you are concerned about your Vitamin D level, status can be established easily through a blood test.  There are a number on the market, but you can also ask your healthcare provider to organise one for you too.