Immunity Victoria Bell Immunity Victoria Bell

What is Vitamin D Deficiency?

Do you struggle more and more with your immunity or your moods as the winter goes on? Do you feel your best when the sun is shining and you’re getting lots of natural daylight? Have you been told that Vitamin D might help?

woman in sun - source of vitamin d

What is Vitamin D?

Vitamin D is actually a hormone, and like vitamins is vital for our health and survival. Also like some vitamins, the body cannot produce it without consuming in the diet and from natural sunlight. Our skin absorbs UV-B sunlight, creating a prohormone which is then converted to 25-hydroxyvitamin D, or Vitamin D3. The amount of Vitamin D you absorb and convert from daylight depends on tiny proteins called Vitamin D Receptors (VDRs).

What Does Vitamin D Do?

It may be best known for supporting immunity, but Vitamin D also:

  • Ensures calcium is absorbed to be stored in the bones, preventing fracture risk and osteoporosis

  • Is needed for muscle contraction and strength

  • Supports healthy lungs

  • Manages blood pressure and therefore protects the heart and arteries

  • Is involved in regulating kidney function

  • Contributes to stable moods

  • Plays a part in appetite control and weight management

  • Supports brain health and cognitive function

How do You Know if You are Vitamin D Deficient?

Symptoms can be vague, hard to pinpoint and overlap with symptoms of many other deficiencies and causes. Typical symptoms might include:

  • Tiredness

  • Muscle aches or weakness

  • Reduced endurance

  • Bone pain

  • Frequent respiratory illnesses

  • Frequent infections

  • Low moods and depression

  • Irritability

  • Infertility

  • Psoriasis

  • High blood pressure

Testing for Vitamin D levels is a standard blood test that your GP can request for you. Many surgeries have a nurse who can take the blood test there for your convenience. While serum 25 Hydroxyvitamin D under 50 nmol/L may be considered to be deficient, the optimal level is over 75 nmol/L.

What Causes Vitamin D Deficiency?

Some groups are considered to be at increased risk of deficiency, including:

  • People with darker skin

  • The elderly living in residential care

  • Those who are institutionalised

  • People who cover up most of their skin or spend little time outdoors

There is another cause for chronic vitamin D deficiency which involves a group of individuals who have a genetic alteration to the VDR gene. For these people, their DNA isn’t as efficient in instructing the body to produce Vitamin D Receptors compared to someone who doesn’t have the alteration. With less VDRs, less Vitamin D can be absorbed and converted.

A genetic test can identify whether you have this genetic alteration (also knows as a mutation or polymorphism). Some DNA profiles available in the UK test for genetics that we can reliably associate with potential health outcomes or dietary requirements. For some people identifying this VDR polymorphism can equip them to start a discussion with their doctor about whether they have an increased requirement for Vitamin D compared to the average person.

Identifying the optimal dosage for that individual can involve a process of trial and error until the right dosage is reached. In this case a doctor may prescribe an especially high dosage for a few weeks or months if the serum Vitamin D level is really low. These individuals often need to take a higher dosage of Vitamin D than a person without an increased need and may benefit from supplementing all year round.

Getting Vitamin D Through Food

We can consume some Vitamin D produced by other animals in the form of oily fish, cod liver oil, beef liver, egg yolks and cheese. Some foods are fortified with Vitamin D such as some dairy alternative milks, but if you are dairy free it is worth checking the label to make sure that they are fortified. Some mushrooms also contain a little Vitamin D. But these foods only contain small amounts and even if you are including plenty of animal-based foods in your diet it is unlikely that this will meet your daily needs.

Sunlight and Vitamin D

Natural daylight is by far the best way to meet your needs for Vitamin D during the spring and summer. It is recommended to get at least 20 minutes of light exposure on your skin, so doing so before the peak hours of sun before applying sun cream is recommended. Exposing arms and legs also helps absorb more Vitamin D. During most of the autumn and winter, the sunlight isn’t strong enough to provide enough Vitamin D for the average person. The NHS recommends that everyone considers supplementing with Vitamin D between October and March. Here’s more information about what the NHS recommends for Vitamin D deficiency.

Types of Supplements

According to the NHS, 10 micrograms which is equivalent to 800 IU (International Units) is adequate for non-risk groups. Many supplements are likely to come in 1000 IU doses which is still well within the safe range for individuals without an increased requirement.

Vitamin D can be found in many multivitamin supplements. If using a multivitamin, it is worth checking whether the dose is at least 10 micrograms or 800 IU to make sure you meet your daily requirement. You can also buy Vitamin D as a supplement on its own, or in formulas designed to support bone health. Including Vitamin K2 with the Vitamin D can also be beneficial. Capsule form suits some individuals, while some may find spray or drop forms are more easily absorbed.

Ensuring that children have adequate Vitamin D intake is also very important, especially for infants. See the NHS’s guidance on what is best for young children. Children’s Vitamin D can also come in a variety of formulations, including jellies, drops and sprays.

Tracking Your Vitamin D

It can take a while to feel the benefit of improving your Vitamin D levels. Retesting after a few weeks if you have previously been deficient can help to ensure that your level is within the optimal range. You can also ask your doctor to test your Vitamin D levels if you know at certain times of year you might be at risk of deficiency or you recognise familiar symptoms arising. Being aware of your requirement and how to make sure you are getting enough will help you to feel better in yourself in the long-run.


If you would like advice on how nutritional therapy can support your immunity, contact me at info@victoriabellnutrition.co.uk

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