Vitamin D Deficiency – A Modern World Epidemic with Huge Consequences

Nature intended that enough Vitamin D is produced by exposure of skin to sunlight

Vitamin D is critical to good health

Many of us know that our bodies can make Vitamin D when our skin is exposed to sunlight and in a previous blog, I discussed how human migration has been a major factor in our current epidemic of Vitamin D deficiency.

Here, I’m going to discuss some of the critical roles of Vitamin D and why we should all make sure that we are making or taking enough.

What is enough Vitamin D?

Oops! Unfortunately, the answer to this question is that no-one knows that answer!

In a recent publication called ‘Trends in Vitamin D Status around the World’[1] the authors noted that although guidelines for Vitamin D levels have been published by the Institute of Medicine, the Endocrine Society, the European Food Safety Authority and the European Calcified Tissue Society, there was no consensus between these august bodies on what constitutes Vitamin D deficiency.

Moreover, a recent publication[2] entitled ‘The big Vitamin D mistake’ refers to two other major findings: (a) There has been a major statistical error in the calculation of the recommended dietary allowance of Vitamin D and that 8895 IU/day are needed for 97.5% of individuals to achieve values of more than or equal to 50 nmol/L. (b) Levels of less than 75 nmol/L (which are commonly regarded as above average) may be too low for safety and may be associated with high ‘all cause’ mortality! The new suggested target Vitamin D level for optimal health is given as 100 nmol/L

Dietary Sources

Unfortunately, there are few foods that contain much Vitamin D. Significant amounts are only present in fatty fish (especially wild fish) and fish liver oils. There are small amounts in beef liver, some cheeses and egg yolks. Some foods are fortified with Vitamin D to attempt to counteract this.

Vitamin D Deficiency, Illness and Mortality

Vitamin D plays critical roles in almost every one of our organs, including our SKIN and our BRAINS.

SKIN: Vitamin D deficiency is associated with many inflammatory skin diseases and this big topic is discussed in detail in an article titled ‘Vitamin D and the Pathophysiology of Inflammatory Skin Diseases’[3]. This article explains the very important functions that Vitamin D plays in the skin, and I recommend that anyone with skin problems downloads it and shows it to their doctor!

BRAINS: In our brains, Vitamin D deficiency is associated with depression and brain cancer.

HEART AND BLOOD VESSELS: In our cardiovascular system, Vitamin D deficiency is associated with strokes and ANY heart disease!

IMMUNE CELLS: Our immune function is highly dependent on Vitamin D and Vitamin D deficiency is thought to be the cause of many if not all the now commonly diagnosed autoimmune diseases. The strongest evidence is for Multiple Sclerosis and Type 1 Diabetes!

Although not an autoimmune disease, Type 2 Diabetes is also associated with lowered levels of Vitamin D.

CANCER: Almost all CANCERS are associated with Vitamin D deficiency, but the evidence is strongest for BREAST CANCER, OVARIAN CANCER, COLON CANCER, PROSTATE CANCER, PANCREATIC CANCER and as mentioned earlier brain cancer.

Vitamin D deficiency is also very strongly associated with INFECTIOUS DISEASES, especially COVID 19!

MUSCLES & BONE: Finally, there is a strong association between low Vitamin D and loss of muscle strength but only a slight relationship with bone health – which is the major reason Vitamin D is given as a supplement! For bone health, Vitamin D is only proven to have an effect when it is taken in conjunction with Calcium.

Indoors, Covering-up, Sunscreens and

Vitamin D deficiency

For us to synthesize our own Vitamin D, our skin needs to be exposed to sunshine! This should be very easy in countries with sufficient sunshine but modern ‘indoor lifestyles’, shift work, religious rituals of covering up and over-zealous protection against sunburn with the goal of preventing skin cancer – have all contributed to Vitamin D deficiency.

Most sunscreens still allow enough exposure to sunlight for us to produce Vitamin D, but it is important to allow yourself enough but not too much exposure to sunlight. For most of us it might be easier to either focus on eating more fatty fish, sipping cod liver oil (ugh) or taking a Vitamin D supplement.


[1] Lips P, de Jongh RT, van Schoor NM 2021: Trends in Vitamin D Status around the world JBMR Plus (Special Issue) 1-6

[2] Papadimitriou DT 2017: The Big Vitamin D Mistake, J of Preventative Medicine & Public Health. 50:278-281

[3] Umar M et al (2018) Vitamin D and the Pathophysiology of inflammatory skin diseases. Skin Pharmacology & Physiology 31: 74-86

Published by Dr Judy

I am a PhD Geneticist and have spent many decades working in research related to reproduction and cancer. Both are affected by lifestyle, especially ageing and so I am passionate about teaching people how to change their lifestyles to optimise their health.

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