top of page

Why is Vitamin D Deficiency Common?

Why are so many people Vitamin D deficient these days? Is it because some of us now have a lifestyle largely spent indoors as we are wary of the effects of sun on our skin? Or is there another possible explanation - like dietary reasons, medication usage and ageing? Let's explore why Vitamin D deficiency is so common.

How is Vitamin D produced?

Vitamin D actually acts as a hormone rather than a vitamin as its name would imply. Vitamin D3 (cholecalciferol) is produced when the sun and its UVB rays activate the precursor to cholesterol in our skin. This Vitamin D3 gets converted to inactive Vitamin D known as 25(OH)D or calcidiol in our livers, and then to the active form of Vitamin D known as 1,25(OH)2D or calcitriol in our kidneys. The same process occurs if we are supplementing or consuming Vitamin D rich foods e.g. oily fish.

If we have Vitamin D levels tested in our blood, it is the inactive 25(OH)D form that is tested first. If this value is considered low, the 1,25(OH)D or active form is then tested. A level of 60ng/mL 25(OH)D (inactive form) is required for disease prevention. This equates to the highest amount generated by the sun.

For the production and absorption of Vitamin D to occur in our bodies, we need Magnesium at every step of the way. Given that 2/3 of the population is magnesium deficient, we can start to see why Vitamin D deficiency is now so prevalent. Magnesium deficiency is largely driven by our modern processed food diets lacking in magnesium, and lifestyle choices that may result in the requirement for medications that further deplete magnesium levels. Medications can include antibiotics, diuretics, antacids, steroids etc Being insulin resistant and having high levels of insulin can also interfere with magnesium levels. Ageing is also linked with a gradual magnesium deficiency. In the absence of magnesium, our whole body and its processes is impacted by Vitamin D deficiency.

Pathway showing conversion of Vitamin D and its active constituent, with all steps requiring Magnesium
Vitamin D Metabolism and Magnesium

Explanation to why Vitamin D Deficiency is so common

It is easily seen by the graphic above, that as a start we need to consume more Magnesium to improve Vitamin D deficiency, as magnesium is required at every step of Vitamin D metabolism and absorption. Why are we so depleted of magnesium these days? A diet of processed foods has a major impact here as it increases our phosphate levels in our blood, with subsequent decrease of magnesium. For a full understanding of why so many people are magnesium deficient, please read the blog on Magnesium Deficiency is common.

Additionally, we can start to see that if our liver and kidney health is suboptimal, the process won't work efficiently, so our detoxification pathways need to be open and clear, and our organs need to function optimally.

Vitamin D deficiency in return plays a key role in Magnesium metabolism, by both stimulating magnesium absorption as well as reducing magnesium excretion from our kidneys.

It is a vicious cycle: Magnesium deficiency leads to Vitamin D deficiency, that in turn leads to more Magnesium deficiency.

As a reminder, to stop this vicious cycle, we must start with supplementing Magnesium first, as too much Vitamin D supplementation can also induce depletion of magnesium.

Unfortunately, as only 1% of magnesium is found in blood, testing for magnesium levels is not a reliable indicator of magnesium deficiency. Symptoms are taken into consideration to assess the extent of magnesium deficiency.

Vitamin D link to Calcium in our Bones

When we think of Vitamin D, we tend to think of it for calcium and for bone health and strength. Vitamin D is so important for calcium absorption in our bones. If we are Vitamin D deficient, we are often Calcium deficient resulting in a generalised decrease in bone mineral density (BMD) that can result in bone and muscle pain, osteopenia and osteoporosis. Vitamin D deficiency is linked with calcium deficiency. As magnesium is needed for Vitamin D synthesis and absorption, we can now see with magnesium deficiency why so many people have calcium issues and osteoporosis these days.

As well as magnesium, we also need to have Vitamin K2 to ensure the calcium that Vitamin D3 helps create ends up in the right spot in our body - in our bones and not our soft tissues (like artery walls). If there is an imbalance between Vitamin D3 and Vitamin K2, excess calcium can end up in our soft tissues instead of our bones as shown by the graphic below.

Vitamin D3 and Vitamin K2 are required to direct Calcium into our bones.

Graphic showing the two routes calcium deposition can take (to the bones or soft tissue)  depending on the balance between Vitamin D and Vitamin K
Synergism between Vitamin D3 and Vitamin K2

Connection between Chronic Inflammation and Vitamin D Deficiency

Vitamin D intervenes and regulates our immune system and associated inflammatory processes by balancing the anti-inflammatory and pro-inflammatory pathways in our body. Without sufficient Vitamin D levels, inflammation can be left unchecked, and so the process of low grade chronic inflammation can persist, with ultimate chronic disease association.

Vitamin D receptors are present everywhere in our bodies - bones, intestines, brain, breast, prostate, lymphocytes etc. Vitamin D can protect against diabetes, osteoporosis, osteoarthritis, high blood pressure, cardiovascular diseases, insulin resistance and metabolic syndrome, depression, autoimmune diseases, cancer of the breast, prostate, colon etc. Elevated levels of inflammation contribute to an increased risk of mental health issues, cardiovascular issues, metabolic issues etc. The graphic below shows the impact Vitamin D deficiency can potentially have on our entire body.

Graphic showing all the body systems impacted by Vitamin D deficiency
Vitamin D Deficiency Impacts on the Body

An analogy for you to remember

If we consider the movement of some vitamins and minerals into the cells in our body, it may be useful to visualise this little picture.

  • Consider magnesium as the boat. Without the boat, no movement of vitamins and minerals occurs.

  • Calcium is the load on board the boat.

  • Vitamin D3 (and Vitamin B6) are the engines of the boat

  • Vitamin K2 can be viewed as the dock - receiving and welcoming calcium into the correct port, which is our bone cells, muscle cells, or for heart function (and ensuring calcium is not sent to the incorrect port - our soft tissue cells like artery walls where we can develop atherosclerosis).

  • Our Parathyroid hormone levels act as the wharf controller, and determine if calcium is required in our bodies and determines where the calcium load is deposited, or removed. It relies on the engine, Vitamin D3, to bring the load in.

  • Taurine (an amino acid that is protective of our heart) acts as the handbrake to prevent too much calcium build up in our cells (too much load taken off the boat).

  • Lysine (another amino acid useful for controlling viral replication inside our cells) acts as the wharf clean up team if calcium is deposited by grinding away the membranes of our virus-infected cells, and acting like a fire-retardant on the virus. Viruses need protective barriers around their homes (our cells) for them to replicate inside our cells. Without the membrane protection, they can't replicate, so Lysine is very helpful at the onset of viral infection e.g. cold sore infections and other viral infections.

The takeaway message is - start with an adequate magnesium supply. See the link for how to obtain this via our diet. Supplementation may be required.

If you would like to discuss your personal circumstances and discuss your Vitamin D and other nutritional needs to get on the road to improving your health, then please don't hesitate to make a booking with me.

Sign Up for Further Educational Material

If you would like to make sure you don't miss a Blog update from me, or would like to receive more information in the form of upcoming e-Books and Online courses, then please subscribe to my mailing list at the bottom of the Blog front page.



The information provided in this blog/article/handout is for your personal or other non-commercial, educational purposes. It should not be considered as medical or professional advice. We recommend you consult with a GP or other healthcare professional before taking or omitting to take any action based on this blog/article/handout. While the author uses best endeavours to provide accurate and true content, the author makes no guarantees or promises and assumes no liability regarding the accuracy, reliability or completeness of the information presented. The information, opinions, and recommendations presented in this blog/article/handout are for general information only and any reliance on the information provided in this blog/article/handout is done at your own risk. Any third-party materials or content of any third-party site referenced in this blog/article/handout do not necessarily reflect the author’s opinion, standards or policies and the author does not assume any liability for them whatsoever.

Recent Posts

See All


bottom of page