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 has many important roles, such as:

  • Regulation of our immune system (1,2)
  • Gut barrier function (3)
  • Helping to reduce inflammation (4)
  • Regulating levels of calcium and other nutrients in the blood needed for healthy bones, teeth and muscles.

Vitamin D Deficiency

According to national surveys (Public Health England National Diet and Nutrition Survey), 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 or SAD (Seasonal Affective Disorder)

Many of you will be familiar with the term SAD, where you may experience symptoms of depression as the seasons change. There is evidence to suggest that there is an association between Vitamin D and serotonin (our happy hormone) levels, which in turn affects our mood. Similarly, one study has shown that Vitamin D supplementation improved depressive symptoms in overweight and obese individuals (7).

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. Please note: Vitamin D needs to be converted into its active form (D3) which is preferred by the body so always look out for supplements containing Vitamin D3 (Calcitriol).

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 quantities 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, please get in touch to discuss your options.

Written by Zara Syed, Registered Nutritionist (mBANT) at APPI
MSc BSc (Hons), DipION, CNHC

Zara is a Registered Nutritionist, with a degree in Biochemistry and a Masters in Clinical Neuroscience. In a world where we are overwhelmed with confusing and often conflicting information around what a healthy diet should look like, Zara offers the opportunity to set up a clear path towards optimal health, through bespoke nutrition programmes.

Instagram: @ZaraSyedNutrition
Facebook: @ZaraSyedNutrition

*****This blog is not intended or implied to be a substitute for seeking professional medical advice, treatment or diagnosis. Information provided here is general, and not intended to treat, diagnose, prevent or cure any disease or conditions. Please contact your GP or private health consultant, if you have any personal health concerns, or consult a registered nutritional therapist for personalised dietary and lifestyle advice and guidance.


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: [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: [Accessed 19 Dec. 2019].