Can vitamin D help prevent colds and flu?

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Can vitamin D help prevent colds and flu?

Vitamin D is in the news again! According to the authors of a recent study, supplementing with vitamin D can help protect against colds and flu, and adding vitamin D to food would have the effect of saving the NHS a significant amount of money. 

New research

The importance of vitamin D in the normal functioning of the immune system is well-established, and the results of a large-scale review, published in the January 2017 edition of the British Medical Journal, suggest that vitamin D supplementation can cut the risk of respiratory infections, such as colds, flu and pneumonia.

The fortification of milk with vitamin D is already common practice in the US, and the UK government recently commented that food fortification might be a valid method of addressing the low vitamin D levels often observed in the population. The researchers involved in this latest study say that a lack of vitamin D during the dark months of winter is in part to blame for the seasonal increase in colds and flu, and that a regular intake of the “sunshine vitamin” is more effective in boosting the immune system than a one-off high dose.

The study was undertaken at Queen Mary University of London, and, led by Professor Adrian Martineau, the team involved in conducting the research reported that a benefit was seen in everyone who took a regular supplement of vitamin D. However, the greatest effect was observed in those people who are typically at an increased risk of vitamin D deficiency.

Annually, respiratory infections affect around 70% of the UK population and they are the most common reason for a trip to the doctor’s surgery. Infections, such as flu, bronchitis and pneumonia, account for 300,000 hospitalisations, and result in approximately 38,000 deaths. Martineau’s team claim that regular vitamin D supplementation would significantly reduce the annual rate of respiratory infections, and would result in 3.25 million less people suffering each year.

Who is at risk of vitamin D deficiency?

Populations groups who are most likely to be lacking in vitamin D include:
  • People with darker skin. The darker your skin the more sun you need to get the same amount of vitamin D as a fair-skinned person.
  • People who spend a lot of time indoors during the day. For example, people who work nights
  • People who cover their skin all of the time. For example, if you wear sunscreen or if your skin is covered with clothes.
  • Older people, who tend to have thinner skin than younger people, meaning that they can’t produce as much vitamin D.

How do I know if I am deficient in Vitamin D?

The clinical features of Vitamin D deficiency in adults include:
  • Joint pain
  • Muscle weakness
  • Calcium deficiency (a late effect) which might result in seizures and muscle spasms

However, some people may not even be aware that they are deficient. The symptoms of vitamin D deficiency are sometimes vague, and can include tiredness and general aches and pains. Some people may not have any symptoms at all. The only true way of assessing vitamin D status is a blood test, and if you think that you may have a vitamin D deficiency, you should see your GP.

According to health watchdog, NICE, around 1 in 5 adults and 1 in 6 children have low vitamin D status. There is a large difference between a clinical deficiency and a sub-optimal status, but these statistics still highlight how vitamin D status among the general population is a cause for concern.

What is the current advice on vitamin D?

Recently, there was a change in the advice given by the government regarding vitamin D intake. Previously, Reference Nutrient Intakes (RNIs) were only set for groups considered at particular risk of vitamin D deficiency. An RNI of 10 µg (400 IU) has now been proposed for the UK population (aged 4y and above) in general. The new advice includes a recommendation that adults and children over the age of 1 year should consider taking a daily supplement containing 10mcg of vitamin D, particularly during the months of autumn and winter.

Our opinion

The universal implementation of Vitamin D food fortification would reliably provide an additional source of vitamin D, and would likely play a major role in reducing the incidence of deficiency in the UK population. However, such a radical move is unlikely to happen overnight, and the results of the recent study reiterate the government’s latest take on vitamin D, which is that there are many people in the UK that would benefit from taking a supplement.

Dietary sources of vitamin D are few and far between, and in the UK we can’t always count on the sun to provide us with the amount we need. In addition to the potential benefits it has to the immune system, supplementing with vitamin D can contribute to maintenance of healthy bones, teeth and muscles, and until food fortification becomes standard practice, we recommend that you follow the existing official advice to take a daily vitamin D supplement of at least 10ug a day. 
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