Vitamin D

Vitamin D has many functions in the body – it mediates and regulates calcium absorption and phosphate levels which are essential for bone building and teeth, and general mineral homeostasis. Frankly there is no doubt about its crucial role in the development and maintenance of a healthy skeleton.

What Happens When You Have A lack Of Vitamin D?

Vitamin D deficiency is a global issue especially in the time of the COVID-19 pandemic. Approximately 18% of the general US population has insufficient vitamin D concentrations {25-hydroxyvitamin D [25(OH)D] between 30 and <50 nmol/L}.

Any absence of vitamin D in the diet and rickets develops which is a bone deformity as does osteomalacia which is pain in the bone. We also know that low serum levels of 25-hydroxyvitamin D [25(OH)D are consistently associated with the presence of chronic disease risk factors, including hypertension, and predict future diseases such as cancer, cardiovascular disease, diabetes, and even mortality.

The receptor for the active form of vitamin D which is 1,25-dihydroxyvitamin D us literally found in every tissue. That’s a testament to how important it truly is to our general well-being.

Recent research has strongly shown that vitamin D3 helps stave off colds and flu.

Rickets was always associated with poor nutrition in people suffering considerable poverty. Many children growing up in Victorian slums and the rookeries developed bowed legs and curvature of the spine. The condition was thought to have been consigned to the history books in Britain when vitamin D was added to our everyday foods such as margarine and cereal back in the 1940s. Cases of rickets dropped but then the number of children admitted to hospital started to double relatively recently in the past decade from 200 in 2004-05 to 455 in 2013-14.

Sources Of Vitamin D

sardines, a source of vitamin D. Photo by Graeme Weatherstone. Courtesy of

When the nights begin to draw in and the opportunity to be exposed directly to sunlight means there is less opportunity for the body to manufacture its own vitamin D [25-hydroxyvitamin D [25(OH)D]. If we are out in the sun, we only need 10 to 15 minutes each day to boost our vitamin D levels. We can of course obtain small amounts eating oily fish like salmon, sardines and mackerel, eggs, fortified butter-like spreads, powdered milk and fortified breakfast cereals. It has long been the case that vit. D supplementation is exceptionally important for those who do not eat eggs, milk or fish and literally cover themselves up.

Benefits Of Vitamin D

Vitamin D is extremely important as it helps to build bones, prevents hypocalcaemic seizure and rickets, it reduces the risk of diseases from cardiovascular to diabetes and cancer, and generally boosts our immunity. It is really a prohormone rather than a vitamin because it carries out is functions by acting on nuclear based receptors (DeLuca, 2004).

It seems though that many of us do not have enough vitamin D3 in us despite the benefits. Indeed, from the evidence of a conference in 2008 on vit. D intake, at least half the population in the USA for example are below the optimal level and 10% of children are classified as deficient in the vitamin (Brannon et al.,2008). If the serum level is below 20 nmol/l, the deficiency can lead to rickets and osteoporosis. Levels above this are less debilitating, coloured by the fact that the optimum level for everyone is not clear because it is multi-factorial. Some researchers think 60 nmol/l in the blood is too little because of the impact the vitamin has in the body. Medics test blood serum levels, and are prescribing supplements though to counter the deficiency. That supplement business is worth nearly $250 million in the USA based on some 2011 figures because about 1 in 5 citizens take this vitamin in some form or other.

Should We Supplement With Vitamin D ?

Recent reports have questioned whether supplementation is worth it.

A number of observational studies have highlighted how high vitamin D supplementation reduces the risk of cardiovascular disease by up to 58%, diabetes by 38% and colorectal cancer by 33%. However, clinical trials with this vitamin in supplementation did not show a clear reduction in risk, even in those with low D vitamin levels to begin with. Likewise, assessment of supplementation in randomized trials found no positive effect on preventing these diseases. A very recent report suggests that supplementation is not required for healthy adults (Autier et al., 2014). They had conducted a meta-analysis on over a hundred studies which complemented similar work on vit. D supplementation on bone mineral density (BDM).

heart tied to a rope on a tree trunk
Image by congerdesign from Pixabay

One of the issues on deciding on how much of the vitamin is good for you, is the scarcity of intervention studies which compare supplementation with vitamin and a placebo. It is still not clear whether overdosing might be a health issue too. One study, the VITamin D and OmegA-3 triaL (VITAL) which is assessing the link between vitamin D intake and improvements to cardiovascular health suggests the pills are not needed. If serum vitamin D levels can be improved by just being briefly outdoors, say an extra 20 minutes for example to increase exposure to the sun, then we are doing ourselves a lot of good.

Helps With Immunity And Puts A Stop To Inflammation

Vitamin D is known to support immunity which means it may well be a critical compound in the fight against COVID-19 for example. There is considerable interest in how it helps in the fight against viruses as well as bacteria.

Any evidence for the immunity benefits ? One study from 2017 assessed 25 randomized control trials comparing vitamin D supplements to placebos (Martineau et al., 2017). The research was conducted by scientists from Queen Mary University of London. They found that the vitamin reduced the risk of acute respiratory infection with either a daily or weekly dose of supplementation. This was especially helpful in people who were vit. D deficient although the lead author has doubts about the evidence where COVID-19 is concerned.

Image by Tim Hill from Pixabay

We know that if you live at high latitudes and through a winter season, these are risk factors for increased influenza, other respiratory illnesses and with it a low level of vitamin D in the body. The consequences are echoed in a similar way with the higher mortality levels from COVID-19 infection. 

A rapid review of the evidence to support the idea that the sunshine vitamin could reduce the risk of coronavirus infection was launched. It came about because of strong concerns that a disproportionate number of asian, black and other minority ethnic people were contracting the virus and dying from the disease. Higher levels of melanin in the skin means less absorption of sunlight to produce vitamin D.

It was reported in various newspapers that Paul Chrisp, the Director of the centre for guidelines at NICE in the United Kingdom stated in 2020:-

“While there are health benefits associated with vitamin D, our rapid evidence summary did not identify sufficient evidence to support the use of vitamin D supplements for the treatment or prevention of Covid-19.”

“We know that the research on this subject is ongoing, and Nice is continuing to monitor new published evidence.”

It still remains to be seen though just what the link happens to be. Is it an association, a cause or a correlation ? From the outset though, vitamin D does not prevent infection by the coronavirus.  

Helps Improve And Strengthen Oral And Dental Health

Given that vitamin D helps the body to absorb calcium, it isn’t surprising that it would play a vital role in dental and oral health. Its presence helps lower the risk of gum disease and tooth decay.

woman with open mouth on a red background.
Image by Alexandr Ivanov from Pixabay

Way back in 2011 (Stein & Tipton, 2011), a review noted an ’emerging hypothesis’ that vitamin D was needed for good oral health because of its effect on bone metabolism.. It also has an “ability to function as an anti-inflammatory agent and stimulate the production of anti-microbial peptides.”

Vitamin D And Cancer.

Reduced levels of circulating vitamin D in the body have been linked to reduced survival for those with melanoma. The mechanisms are poorly understood.

Melanoma is generally very aggressive and difficult to treat. However survival rates have doubled in the UK for example in only the past 40 years. About 300 people are diagnosed with melanoma in its late stages in England each year. About 55% of people with this very late stage form of melanoma survive the disease for 1 year or more compared to 100% when it is diagnosed at the earliest stages. 

Recent evidence points to vit. D affecting the behaviour of melanoma cells which makes them less aggressive. Cancer Research UK researchers at the University of Leeds established that this vitamin can affect the behaviour of the signalling pathways in the melanoma cells. It slowed their growth and stopped spreading to the lungs. The research was published in the journal Cancer Research November, 2019 (Muralidhar et al., 2019).

Vitamin D And Mental Health Issues

A recent examination of vitamin D suggest that it is no cure for depression as is sometimes stated. It was thought that because many people suffer from a Winter depression through lack of sunlight that vitamin D was implicated. No so ! (Jorde & Grimes, 2019).

The Scientific Advisory Committee on Nutrition (SACN) which advises the government on nutrition is reviewing vitamin D for all population groups in the UK. This short post does not do justice to the great wealth of date available and I will be adding pertinent information as it appears. I would be interested to know of other thoughts on whether they take this vitamin in whatever form, as a supplement and whether they perceive it has done them some good.


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The products and the information provided about specific products on or through this site have not been evaluated by the United States Food and Drug Administration or by any other national regulatory body and are not intended to diagnose, treat, cure or prevent disease. The information provided on this site is for informational purposes only and is not intended as a substitute for advice from your physician/doctor or other health care professional or any information contained on or in any product label or packaging. You should not use the information on this site for diagnosis or treatment of any health problems or for prescription of any medication or other treatment. You should consult with a healthcare professional before starting any diet, exercise or supplementation program, before taking any medication or if you suspect you might have a health problem.


Autier, P., Boniol, M., Pizot, C., Mullie, P. (2014) Vitamin D status and ill health: a systematic review. Lancet Diabetes & Endocrinology. 2(1) pp. 76-89
Brannon, P.M., Yetley, E.A., Bailey, R.L. Picciano, M.F. (2008) Overview of the conference “Vitamin D and Health in the 21st Century: An Update” Am. J. Clin. Nutr. 88 pp. 483S-490S
DeLuca, H.F. (2004). Overview of general physiologic features and functions of vitamin D. Amer. J. Clin. Nutr. 80 pp. 1689-1696

Jorde, R., & Grimnes, G. (2019) Vitamin D: no cure for depression. Amer. J. Clin. Nutr. 110(5) pp. 1043-1044 (Article)

Martineau, A.R. et al., (2017) Vitamin D supplementation to prevent acute respiratory tract infections: systematic review and meta-analysis of individual participant data  BMJ ;356:i6583 (Article)

Sathya Muralidhar et al, (2019) Vitamin D-VDR signaling inhibits Wnt/beta-catenin-mediated melanoma progression and promotes anti-tumor immunity, Cancer Research. DOI: 10.1158/0008-5472.CAN-18-3927

Stein, S.H., Tipton, D.A. (2011) Vitamin D and its impact on oral health–an update. J Tenn Dent Assoc. 91(2) pp. 30-35 (Article)

Zhang, X. (2020) Vitamin D and Depression in Puerto Ricans Living in the United States, The Journal of Nutrition, Volume 150, Issue 12, December Pages 3047–3048 (Article

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1 Comment

  1. Really useful knowledge here on vitamin D. I often look at some of your other articles just to check if the medics are telling the truth about these supplements. I get a bit fed up with those writers that just want to tell you how good snake oil really is. Your pages do have a ring of authenticity about them and not some computer generated nonsense.

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