THE SUNSHINE VITAMIN
What is it and why do we need it?
Vitamin D is fat soluble, meaning it is dissolved in fats and oils (e.g. avocado, olive oil, nuts and seeds) and stored within the fat cells of our body.
Unlike other vitamins, it is better classified as a steroid hormone, since 90% of our Vitamin D is actually made from cholesterol when our skin is exposed to the sun and hence referred to as the “sunshine vitamin”! The amount we make will vary depending on your skin colour, with fairer skinned individuals typically requiring less exposure than those with darker skin.
Vitamin D plays a crucial role in immune regulation (1,2), gut barrier function (3), inflammation (4) and regulating levels of calcium and phosphorous in the blood needed for healthy bones, teeth and muscles.
Vitamin D Deficiency
According to national surveys (Public Health England National Diet and Nutrition Survery), 23% of adults in the UK have low levels of Vitamin D (5).
So it won’t come as a surprise that you may be at risk of deficiency if you live in the UK or a country where sunshine exposure is particularly limited during the winter months. The same applies if you spend a lot of time indoors, have darker skin or usually cover up most of your skin (5).
The following could all be signs that your levels are low. However, you may be unaware of a deficiency as symptoms are often subtle and non-specific.
Commonly catching colds and infections (6)
Fatigue and low energy
Bone pain or bone loss
Back Pain
Poor muscle strength
Hair loss
Low mood (7) or SAD (Seasonal Affective Disorder)
What can you do?
Vitamin D comes in two forms: D2 (ergocalciferol) obtained from some plant sources and yeast and D3 (cholecalciferol) which is found in foods such as egg yolks, fortified dairy products, liver and oily fish. Consuming these foods will ensure you are getting a small amount, however it is difficult to meet the daily requirement through your diet alone.
Public Health England therefore recommend that we should all be supplementing with 400IU (10μg) from October to March (5,8). This includes infants from the age of 1 and women who are pregnant or breast feeding.
*Always look out for supplements containing Vitamin D3 (Calcitriol), which is the active form and preferred by the body.
This is beneficial as a maintenance dose, however if you suspect that you might be deficient, it is essential that you speak to your GP or a nutrition professional to get your blood levels tested. This is to establish the severity of your deficiency and ensure that you are including a high-quality supplement with the appropriate dosage for you. Over supplementing or unnecessarily high dosages can be toxic and harmful to your health.
While Vitamin D is crucial to our overall health and well-being, it is relatively straight forward and simple to address a deficiency.
If you would like to get yours tested or feel you may be at risk of deficiency, feel free to get in touch to discuss your options.
References
1. Saul, L., Mair, I., Ivens, A., Brown, P., Samuel, K., Campbell, J., Soong, D., Kamenjarin, N. and Mellanby, R. (2019). 1,25-Dihydroxyvitamin D3 Restrains CD4+ T Cell Priming Ability of CD11c+ Dendritic Cells by Upregulating Expression of CD31. Frontiers in Immunology, 10.
2. Wei, R. and Christakos, S. (2015). Mechanisms Underlying the Regulation of Innate and Adaptive Immunity by Vitamin D. Nutrients, 7(10), pp.8251-8260.
3. Raftery, T., Martineau, A., Greiller, C., Ghosh, S., McNamara, D., Bennett, K., Meddings, J. and O’Sullivan, M. (2015). Effects of vitamin D supplementation on intestinal permeability, cathelicidin and disease markers in Crohn’s disease: Results from a randomised double-blind placebo-controlled study. United European Gastroenterology Journal, 3(3), pp.294-302.
4. Zhang, Y., Leung, D., Richers, B., Liu, Y., Remigio, L., Riches, D. and Goleva, E. (2012). Vitamin D Inhibits Monocyte/Macrophage Proinflammatory Cytokine Production by Targeting MAPK Phosphatase-1. The Journal of Immunology, 188(5), pp.2127-2135.
5. GOV.UK. (2016). PHE publishes new advice on vitamin D. [online] Available at: https://www.gov.uk/government/news/phe-publishes-new-advice-on-vitamin-d [Accessed 19 Dec. 2019].
6. Schwalfenberg, G. (2010). A review of the critical role of vitamin D in the functioning of the immune system and the clinical implications of vitamin D deficiency. Molecular Nutrition & Food Research, 55(1), pp.96-108.
7. Jorde, R., Sneve, M., Figenschau, Y., Svartberg, J. and Waterloo, K. (2009). S67-02 Effects of vitamin d supplementation on symptoms of depression in obese subjects: Randomized double blind trial. European Psychiatry, 24, p.S318.
8. GOV.UK. (2019). SACN vitamin D and health report. [online] Available at: https://www.gov.uk/government/publications/sacn-vitamin-d-and-health-report [Accessed 19 Dec. 2019].