Can Vitamin D reduce the risk of childhood infection and asthma?!
Vitamin D is crucial for many things in life but recent research is suggesting potential benefit to a child’s immunity against things like ear, nose, throat and even skin infections. Evidence is also emerging about its protective ability around asthma. Particularly important is intake during pregnancy and in childhood years. In this article we look at the science, the factors behind how much Vitamin D you have (most of us don't have enough) and how to make sure you get enough.
The benefits of Vitamin D have been gaining more attention in recent years, particularly related to how it can help the immune system, especially the developing immune system of a growing child. Most interesting is the work emerging about the power of making sure you have enough during your pregnancy and how this may actually influence a child’s immunity later in life (24), specifically the evidence around its ability to potentially reduce the risks around common childhood infections like ear, stomach and even asthma in early childhood.
So what does the science say?
As always with these things, there is no definitive answer, however there is a decent chunk of credible studies showing that vitamin D levels during pregnancy may influence the baby’s immune system development and their susceptibility to infection (24).
A selection of studies in fact have shown that Vitamin D during pregnancy can potentially reduce ear, nose, throat and skin infections in childhood (24). Great!
The trouble is however, there is also decent evidence that many of us (particularly those with darker skin as most absorption comes via the skin) have Vitamin D deficiency including during the crucial time of pregnancy (21, 24).
What about asthma?
Asthma is another condition that relates to a misfiring immune system and inflammation (click here for more), some research is linking increased chance of it developing to lower Vitamin D levels (16). Once again this isn't conclusive, but there are studies ongoing to attempt to confirm. One study found a relationship between how much Vitamin D intake a mother had during pregnancy and asthma symptoms. The study found that higher levels were associated with ‘significantly’ lower odds of hospitalisation for asthma, whereas lower levels were found to be associated with the reverse. (27-3)
Asthma and immune conditions are of course complex and there may be many causes but it does look like Vitamin D during pregnancy could potentially play a role.
What about in older children?
Immunity of course matters not only in the very earliest days and in fact it is not just adults that appear to be Vitamin D deficient. Research has shown that vitamin D deficiency is highly prevalent among children worldwide. One study looking at almost 500 children showed a link once again to higher Vitamin D levels leading to lower risk of gastro (stomach) and ear infections (25-2).
So: it seems increasingly important that getting enough Vitamin D is crucial - but, how much is ‘enough’ and what are the factors that could mean you/your child don’t have enough?
Whilst it is pretty common to not have enough, you also don't want too much (sigh!) as Vitamin D is a fat soluble vitamin which also means you should have too much either (click here for more). So the first and easiest solution is when you are getting one of your many blood tests during your pregnancy is just ensure your doctor checks your level. Easy!
It is always better to check your own (individual) levels than to wildly go around popping supplements which has become more of the norm these days. Speak to your doctor and ask for a test if it hasn’t already been done. Asking never hurts!
What impacts how much Vitamin D you have?
The most significant source of Vitamin D is via sunlight: half an hour of sunlight delivers 50,000 iu of vitamin D with Caucasian skin (3). Worth being aware that skin pigmentation lowers the amount of Vitamin D synthesis that you get from UV exposure so the darker your skin the less you get. (24)
What does 50,000 iu mean?!
These numbers can be confusing - but to put into context: The 2012 recommendation from UK Chief Medical Officers and National Institute for Health and Care Excellence (NICE) guidance states that all pregnant and breastfeeding women should take 10 micrograms of vitamin D supplements daily: that’s equivalent to 400 iu. (17,18)
Another way to put into context: for the majority of women who are deficient in vitamin D, treatment for 4–6 weeks of 20,000 iu a week of Vitamin D3 (ie. around 3,000 IU/day) is recommended. (19,20).
How do you know if you’re deficient?
A blood test is the only way to know and is defined as a level of less than 37.5nmol/l (10,12).
The main risk factors for a low level are:
You live in an area with less sunlight or you spend a lot of time indoors.
During the winter months when the days are shorter
If you always cover your skin and always use high factor sunblock
If you have darker skin
If you are obese (BMI +30)
If you are a Vegan: eggs, oily fish are rich in Vitamin D
Genetics: some people have genetic abnormalities which impact how Vitamin D is metabolised and transported around the body.
How do you get more?
Of course sun exposure is a tricky thing as we are all now more aware of the danger of too much sun! (Never easy is it?!). Everyone is different but the good news is that you don't need to sunbathe. Typically just 15 minutes a day in the sun, two or three times a week, should be enough in sunny weather, and you only need to expose your arms and face. Of course everyone is different and it depends on your skin type, the time of day and the time of year. If in doubt, get your levels tested and avoid too much exposure particularly during the midday heat. Sun Safety is equally important.
What about supplements? What type should I take?
Once again (sorry to keep stressing this!) speaking to your doctor and checking your levels is always good before supplementing with anything. That being said, as above the guidelines are for Vitamin D supplementation for pregnant and breastfeeding women and the research around the benefits for many things including the immunity of a developing baby are compelling so this is definitely something important to be aware and on top of.
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