Vitamin D’s most well known function is to regulate bone metabolism and the concentration of calcium in the bloodstream. However, in recent years, it has been thrust into the spotlight as a potential immuno-modulator.  In the context of the coronavirus pandemic, this has led to speculation about whether we should all be taking vitamin D supplements to protect us against such infections. 

I decided to join Dr Tom O’Bryan and The Nutrition Collective last week to review what the science says on vitamin D, immunity and supplementation.  I have summarised my key takeaways for you below: 

• Our ability to fight off infections is a direct reflection of how well our innate immune system is functioning (PMID: 32105090). 

• A well functioning immune system requires optimal nutritional status, including vitamin D (PMID: 32340216). 

• In systematic review and meta-analysis, vitamin D supplementation has been shown to reduce the risk of, and protect against, respiratory tract infections and is considered safe (PMID: 28202713).

Vitamin D is a group of fat-soluble steroid compounds: Cholecalciferol (or vitamin D3), synthesised in the skin following sun exposure and naturally occurring at modest levels in certain foods such as oily fish, eggs, liver and butter; and ergocalciferol (or vitamin D2), a synthetic form used to fortify foods in some European countries. 

The latitude in the UK makes it virtually impossible to synthesise vitamin D in the skin between October and April, and food sources alone are unlikely to provide sufficient amounts, indicating supplementation might be necessary to achieve optimal vitamin D levels. It is generally accepted based on the evidence that D3 is superior at raising and sustaining levels of serum vitamin D and is therefore the preferred form for supplementation (PMID: 22552031).

A recent study conducted in the US found that circulating levels of vitamin D were inversely associated with clinical severity of coronavirus. Hospitalised covid-19-positive patients with sufficient vitamin D levels experienced fewer clinical complications and had lower mortality rates than those patients who were vitamin D deficient PMID: 32976513.  Whereas another study found that higher levels of circulating vitamin D were associated with fewer infection rates PMID: 32941512. 

So just how much is right for you? Optimal vitamin D status is influenced not only by the amount of sunlight you are exposed to or the amount you ingest but also your ability to absorb and utilise the nutrient. This can be affected by various factors such as genetics, skin colour, diet, weight and prescription medication. 

Dr Tom O’Bryan’s mantra was “test don’t guess”.  Too little may not be effective. Too much may deplete other nutrients such as Vitamin A.  Vitamin D levels can be tested with a simple and affordable finger prick blood test.  Using these results, a health practitioner such as a Registered Nutritional Therapist,  can determine whether supplementation is required and at what level whilst simultaneously ensuring that your diet and lifestyle are optimised for absorption and utilisation. 

Vitamin D testing and personalised advice on optimising your nutritional status in order to support your immune system is available re:Nutrition.  If you would like to find out more about this and other services that we offer, subscribe below or book your complementary discovery call today.