The Marion Gluck Clinic


Vitamin D, the immune system boosting hormone

By Vera Martins

Did you know that Vitamin D is actually a hormone rather than a vitamin? In fact, the final product of Vitamin D conversion in the body is considered a hormone. We can obtain Vitamin D from some foods such as oily fish, egg yolks and whole milk, however 90% of the Vitamin D we get is made by our bodies. The body makes Vitamin D from direct sunlight (particularly UV-B radiation) in the skin and the synthesis process continues in the liver and kidneys, until producing the final active form of the hormone.

Several different types of cells in the body, including immune cells, contain the receptor for Vitamin D, which means they can respond to Vitamin D molecules, triggering different reactions in the body. No wonder Vitamin D can affect so many aspects of health including bone health, cardiovascular health, immunity, autoimmune disease, type I diabetes, and mental health.

But because the cold season is just around the corner, today we are looking at how Vitamin D affects the immune system helping to keep that undesired cold at bay.

Can vitamin D help with colds and the flu?

Absolutely! There is tonnes of scientific research backing up that a deficiency in Vitamin D increases the chances of infection.

A study has shown that individuals with low Vitamin D levels are more likely to develop upper respiratory tract infections than those with sufficient levels. And several studies have reported an association of lower Vitamin D levels and increased rates of infection, including influenza. In a study with Japanese children, daily supplementation with Vitamin D for 15 to 17 weeks during the winter significantly reduced the incidence of influenza infections by 42%, compared with a control. In another study, supplementation with Vitamin D for three months during the winter decreased the frequency of upper respiratory tract infections in children with Vitamin D deficiency.

How does Vitamin D support the immune system?

The role of Vitamin D in the immune system has been recognised for about 35 years, however it was only in recent years that the implications of Vitamin D deficiency on the immune system have become clearer.

There are two types of immune system, equally important in fighting infections, the innate system (responsible for quickly fighting infections) and the adaptive system (which produces a slower response but is highly specialised, e.g. responsible for the production of antibodies). Vitamin D seems to modulate both systems which explains why this hormone has such a wide effect on the immune system. In fact, Vitamin D is also known to play a role in autoimmunity. A prevalence of Vitamin D deficiency is observed in patients with autoimmune disease, including multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease and lupus erythematosus.

 How can I boost my levels of Vitamin D?

Regular exposure to sunlight is the most natural and desirable way to get enough Vitamin D. In the UK sun, aiming for 10-20 minutes of exposure around midday several times a week is usually a good balance between adequate Vitamin D levels and avoiding the risk of skin cancer. During the spring and summer months we are more likely to cover our daily needs of Vitamin D from sunlight exposure.

Vitamin D is stored in the body for approximately 2 months. Therefore, the Vitamin D you stocked up during your much-loved sunny days back in the summer will start going away as the shorter and colder days of winter get closer. Since it is difficult to get enough Vitamin D from food alone, the best way to cover your daily requirements in the winter months is to take a supplement.

Supplements mainly come in two forms, Vitamin D3 or D2, with D3 being more efficient at raising Vitamin D levels in the body. You can find supplements as tablets but also as sublingual drops or spray, which are a great choice for people suffering from malabsorption.


How much Vitamin D should I take?

There is a wide range of expert opinions when it comes to how much Vitamin D we should supplement. According to the Department of Health recommendations, anyone above the age of four should have 10 micrograms (400 IU) daily particularly between October and March. People at higher risk (those with little or no exposure to the sun and people with dark skin) are advised to take a supplement all year round. The Department of Health also states 100 micrograms (4000 IU) as the recommended daily limit.

However, it is important to recognise that Vitamin D requirements can vary greatly according to where you live (people living in northern countries are at higher risk of Vitamin D deficiency), age, season, and individual factors (some people may need more than 400 IU daily if levels are very low). The best way to evaluate your individual needs is to get professional advice from a qualified naturopath or nutritionist.

If you need help managing your Vitamin D levels and boosting your immune system book an appointment with Vera today.

A balanced gut is also key to a healthy immune system – read about gut balancing foods here.

Adorini, L. (2005). Intervention in autoimmunity: The potential of vitamin D receptor agonists. In Cellular Immunology.

Aranow, C. (2011). Vitamin D and the immune system. J Investig Med., 59(6), 881–886.
Baeke, F., Takiishi, T., Korf, H., Gysemans, C., & Mathieu, C. (2010). Vitamin D: Modulator of the immune system. Current Opinion in Pharmacology.
Camargo, C. A., Ganmaa, D., Frazier, A. L., Kirchberg, F. F., Stuart, J. J., Kleinman, K., … Rich-Edwards, J. W. (2012). Randomized Trial of Vitamin D Supplementation and Risk of Acute Respiratory Infection in Mongolia. PEDIATRICS.
Tripkovic, L., Lambert, H., Hart, K., Smith, C. P., Bucca, G., Penson, S., … Lanham-New, S. (2012). Comparison of vitamin D2and vitamin D3supplementation in raising serum 25-hydroxyvitamin D status: A systematic review and meta-analysis. American Journal of Clinical Nutrition.
Urashima, M., Segawa, T., Okazaki, M., Kurihara, M., Wada, Y., & Ida, H. (2010). Randomized trial of vitamin D supplementation to prevent seasonal influenza A in schoolchildren. American Journal of Clinical Nutrition.



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