What is Vitamin D?

Most vitamins cannot be produced by the body so must be obtained from the diet. Vitamin D is different.

When exposed to the sun, your skin can make its own vitamin D. (In fact, it is not strictly a vitamin at all but belongs to a group of fat-soluble secosteroids - a type of steroid hormone).

The two main forms of Vitamin D are:

  • Vitamin D3 (cholecalciferol) - we have vitamin D receptor cells that, through a chain of reactions starting with conversion of cholesterol in the skin, produce vitamin D3 when they’re exposed to ultraviolet B (UVB) from the sun. Vitamin D food sources include oily fish, egg yolks and some fortified foods. Vitamin D3 can also be obtained from supplements.
  • Vitamin D2 (ergocalciferol) – is synthesized from ergosterol - found in some plants, mushrooms, and yeasts.

Of the two, D3 has been shown to be almost twice as effective at increasing blood levels of vitamin D as D2.

How our bodies process vitamin D

After vitamin D is absorbed through the skin or acquired from food or supplements, it gets stored in the body’s fat cells. Here it remains inactive until it’s needed.

Vitamin D needs to undergo two conversion steps to become active. First, it is converted to calcidiol, or 25(OH)D, in your liver. This is the storage form of the vitamin.

Second, it is converted to calcitriol, or 1,25(OH)2D, mostly in your kidneys. This is the active, steroid-hormone form of vitamin D.

Calcitriol interacts with the vitamin D receptor (VDR), which is found in almost every single cell in your body.

When the active form of vitamin D binds to this receptor, it turns genes on or off, leading to chemical changes in your cells.

Why our bodies need vitamin D

Vitamin D has many roles in the body but is particularly important in enhancing intestinal absorption of calcium, iron, magnesium, phosphate and zinc and maintaining a healthy mineralized skeleton. It is also known as an immunomodulatory hormone. Both the vitamin D receptor (VDR) and metabolizing enzymes are expressed by various types of immune cells including lymphocytes, monocytes, macrophages, and dendritic cells. Studies have shown that vitamin D has significant biologic activities on the innate and adaptive immune systems. It has been demonstrated that administration of vitamin D or its metabolites leads to changes in the occurrence and progression of various immune-related diseases. This supports the clinical and epidemiological data that link vitamin D with the incidence and severity of many disorders such as psoriasis, multiple sclerosis, rheumatoid arthritis, type 1 diabetes, and infectious diseases particularly respiratory tract infections like viruses, colds, bronchitis and pneumonia.

Vitamin D deficiency

Vitamin D deficiency means that there is not enough vitamin D in your body. This may be because:

  • Your body has an increased need for vitamin D.
  • Your body is unable to make enough vitamin D.
  • You don't have enough vitamin D in your diet.

How common is vitamin D deficiency?

A lack of vitamin D is very common. One survey in the UK showed that about 1 in 5 adults and about 1 in 5 children in the UK have low vitamin D levels. More people have low vitamin D levels in the winter and spring because of less exposure to sunlight so your body is unable to make enough vitamin D.

People who get very little sunlight on their skin are at risk of vitamin D deficiency. This is more of a problem in the more northerly parts of the world (including the UK) where there is less sun.

Those more likely to be deficient are:

  • People who stay inside a lot. For example, those in hospital for a long time, or housebound people.
  • People who cover up a lot of their body when outside.
  • The use of sunscreen may increase the risk of vitamin D deficiency, particularly if high sun protection factor (SPF) creams (factor 15 or above) are used.
  • Elderly people are unable to produce as much vitamin D. This leaves older people more at risk of vitamin D deficiency.
  • People who have darker skin are not able to make as much vitamin D.
  • Some medical conditions can affect the way the body handles vitamin D. People with Crohn's disease, coeliac disease, and some types of liver and kidney disease, are all at risk of vitamin D deficiency.
  • People who follow a strict vegetarian or vegan diet, or a non-fish-eating diet.
  • People taking certain medicines. Examples include: carbamazepine, phenytoin, primidone, barbiturates and some anti-HIV medicines.

Symptoms of Vitamin D deficiency

Fatigue and Tiredness - Excessive fatigue and tiredness may be a sign of vitamin D deficiency. Research has shown that many people suffering with CFS/ME have low levels of vitamin D.

Bone and Back Pain - Low blood levels of vitamin D may be a cause or contributing factor to bone pain and lower back pain. Studies show that people with vitamin D deficiency were nearly twice as likely to experience bone pain in their legs, ribs or joints compared to those with blood levels in the normal range.

Bone Density Loss - Vitamin D plays a crucial role in calcium absorption and bone metabolism. A diagnosis of low bone mineral density is an indication that your bones have lost calcium and other minerals. This places older adults, especially women, at an increased risk of fractures.

Nerve and Muscle Pain - The vitamin D receptor is present in nerve cells called nociceptors, which sense pain. Vitamin D deficiency has been associated with headache, abdominal, knee, and back pain, persistent musculoskeletal pain, costochondritic chest pain, and failed back syndrome and with fibromyalgia.

Depression - Research has linked vitamin D deficiency to depression, particularly in older adults.

Impaired Wound Healing - Slow healing of wounds after surgery or injury may be a sign that your vitamin D levels are too low. Studies suggest that the vitamin increases the production of compounds that are crucial for forming new skin as part of the wound-healing process. Vitamin D also plays a role in controlling inflammation and fighting infection, both important for proper healing.

Vitamin D deficiency treatment

The treatment is to take vitamin D supplements in the form of vitamin D called ergocalciferol or calciferol. Following an in depth analysis of your individual needs, Claudia, your BioMed Health Practitioner, will determine the most beneficial dosage required as part of your personalised health plan to achieve optimal health and well being.



January 17, 2022

WHAT IS GLAUCOMA? Glaucoma is a group of diseases where the optic nerve, which connects the eye to the brain, becomes damaged.


December 17, 2021

If so, you might have seasonal depression, also known as seasonal affective disorder (SAD).


November 26, 2021

The most frequent form of urinary incontinence in women is Stress Urinary Incontinence, (SUI) defined as "involuntary leakage on effort or exertion, or on sneezing or coughing"


October 26, 2021

Cultivating a happy, calm and motivated mind that finds it easy to concentrate, relax and sleep soundly is not as easy as just willing it to happen...


October 12, 2021

Proprioception is the body’s ability to sense its location, movements, and actions...


September 27, 2021

The menopausal transition will happen at some stage in every woman’s health journey, usually between the ages of 45 and 55.


September 19, 2021

There is a growing body of evidence that depression is linked to increased levels of inflammation in the body and this can be influenced by a number of factors...


September 08, 2021

You mention the word ageing, and most people automatically go to old. There is a lot of ground between ageing and old!


August 27, 2021

To fast or not to fast? That is the question... Fad diets have been a mainstay of the weight loss industry for decades, each season bringing with it a brand new quick-fix diet to help you shed a few pounds, lose a clothing size and achieve the “perfect” body.


August 19, 2021

The thyroid is a butterfly-shaped endocrine gland that is normally located in the lower front of the neck.