There’s been an ongoing debate amongst scientists over whether there’s a link between vitamin D and coronavirus (COVID-19).
Many now believe that vitamin D supplementation could be a useful, protective tool in the fight against the coronavirus pandemic.
In fact, in December 2020, the UK government received updated advice from Public Health England (PHE) and the National Institute for Health and Care Excellence (NICE). After this, they began offering a free 4-month supply of vitamin D supplements to people who are considered clinically extremely vulnerable.
But what evidence is there to support this? This guide looks into the latest research and advice from our leading health bodies to dig deeper into this uncertain topic.
The role of vitamin D
Vitamin D is one of our essential vitamins and has many functions in the body. Its main job is helping to build and maintain a healthy skeleton by keeping the levels of calcium and phosphorus in our blood at just the right amount. Other roles include supporting our metabolism, muscle health, and nervous system.
Vitamin D is also important to our immune system, which helps us to fight off infections.
Sources of vitamin D from food are relatively scarce but include oily fish, liver, red meat, and fortified foods such as some kinds of margarine and breakfast cereals. Instead, the main source of vitamin D is the Sun.
When our skin gets exposed to the Sun’s ultraviolet rays, a chain of reactions begins. This triggers our body to produce many helpful chemicals. One of these is vitamin D. Vitamin D can then move around the body, carrying out its many roles in maintaining our health.
- Vitamin D is an essential vitamin with many important functions in the body
- There are few dietary sources of vitamin D, so our main source is Sunlight
How common is vitamin D deficiency?
The main source of vitamin D is Sunlight. Rates of deficiency increase as we travel away from the equator, where the Sun’s rays are the strongest.
Similarly, vitamin D deficiency is much more common in the winter, compared to the summer months. During summer, it’s more likely to be sunny, and people spend more time outdoors. This means we tend to get enough sunlight to maintain healthy vitamin D levels.
One study found that, in the UK, our vitamin D levels are around 50% lower in February compared to September. This means we are more likely to become vitamin D deficient.
Factors that increase the risk of developing vitamin D deficiency include:
- old age
- regular use of suncream
- darker skin
- spending little time outdoors
- wearing clothes that cover all or most of the body
Similarly, the time of day a person is outdoors, the distance from the equator, and the time of year all play significant roles.
The NHS considers a blood concentration of vitamin D that’s lower than 30nmol/L to be deficient and levels between 30-80nmol/L insufficient.
At least 1 in 5 adults in the UK are deficient in vitamin D. More people are likely to fall into the insufficient category.
Deficiency can have serious health implications such as increasing the risk of developing bone diseases, certain cancers, type 2 diabetes, and high blood pressure.
- Vitamin D deficiency is really common, affecting at least 1 in 5 UK adults
- Deficiency is most common in the winter, and in places that are further from the equator where the Sun’s rays are weakest
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Can vitamin D help our immune system?
Vitamin D helps our immune system, our way of fighting off viral and bacterial infections. A deficiency of vitamin D may impair its function, leaving us more susceptible to infections. Some scientists strongly believe that taking a daily supplement of vitamin D can prevent acute respiratory infections to some degree.
A recent meta-analysis (research that combines the findings of multiple studies) found that there were significant protective effects associated with supplementing vitamin D.
The patients who received a daily or weekly supplement of vitamin D had a slightly lower risk of contracting a respiratory infection than patients who didn’t.
Additionally, the supplemented patients were 17% less likely to require hospital treatment for their infection, suggesting they experienced a less severe illness. Most importantly, the patients who received the supplement were 30% less likely to die from a respiratory infection than those who didn’t.
The researchers also found that daily and weekly doses of vitamin D were the only methods that offered protection. Larger doses delivered monthly didn’t offer any protection from respiratory infections. Similarly, if the patient already had optimal vitamin D status, there were no additional benefits to supplementing.
This offers important insight into the role that our vitamin D status may play in our risk of developing and recovering from respiratory infections. However, other studies have failed to identify this same protective effect. Questions remain over the full effect of vitamin D deficiency on immunity.
It’s important to remember that supplementation of vitamin D only offers small, though significant, benefits that may take months to develop, especially if you’re already very deficient.
- Vitamin D plays an important role in supporting our immune system
- Studies have shown that supplementing vitamin D can reduce the severity and risk of dying from respiratory infections