Why vitamin D really does need the sunshine
Happy 1st February and I guess I can just about get away with saying "Happy New Year" too! When I look back over January two key themes strike me; namely Covid and sunshine and although they seem quite disparate, they actually are connected and were the inspiration for this blog.
In terms of the C word, I (along with my daughter) both tested positive and so had to isolate for 5 days. Luckily we were asymptomatic and tested negative after day 5. However, the start to the new term was a bit disjointed with college closures due to Omicron working its way through the teachers and other members of staff.
The other thing I mentioned that stood out during January was the amazing winter sunshine we were blessed with here in the Pyrenees - already there is an intensity to the sun, hence lots of alfresco lunches on our balcony.
So what has any of this got to do with vitamin D?
Well it has been linked to Covid (see the following paragraph) and it is the only vitamin that can be made directly from sunlight - now can you see where I am coming from?
There has been a LOT of discussion and debate surrounding vitamin D and its many purported functions, especially with relation to immunity and COVID-19. During the early stages of the pandemic some of the patients with severe disease were found to have low circulating levels of vitamin D and so much interest was generated as to whether (i) people were more likely to develop severe COVID if they already had suboptimal vitamin D status and (ii) if supplementing patients with vitamin D could confer a preventative effect. (Ref 1)
Research was already being carried out pre-Covid into possible links between low vitamin D status and the risks of developing acute respiratory tract infections (ARTI’s) based on observational evidence. The arrival of the pandemic (Covid being an ARTI) led to a rapid intensification of interest in this field leading to august bodies such as the National Institute for Clinical Excellence (NICE) (Ref 2) and the Royal Society (Ref 3) both producing rapid reviews of all of the available research. Neither of them found any causal relationship between low vitamin D status and severity of disease - in other words just having a low vitamin D level by itself is not necessarily a precursor to developing severe Covid. Other factors such as age and if you are from a black, Asian or minority ethnic (BAME) were also common amongst people with severe Covid.
A trial started at Queen Mary’s college hospital in London (CORONAVIT) (Ref 4) in 2020 looking in greater detail about the possible role of vitamin D and whether it can reduce the incidence and severity of Covid and other ARTI’s and it will be interesting to find out what they discover.
So what exactly does vitamin D do?
Well moving away from Covid and a possible role involving vitamin D, what we do know for certain is vitamin D plays a vital role in bone and muscle health. It helps our bodies absorb calcium from the gut, calcium (along with phosphorus) is one of the main components of bone. Not enough vitamin D leads to weaker, more brittle bones (in babies this presents as rickets) and as adults osteomalacia. This can of course be devastating to anyone, but is especially important if you are involved in any weight-bearing exercise, such as running, where you need strong muscles and bones in your legs to withstand the impact of the running motion.
How do I get it?
As I mentioned at the beginning there is a connection between vitamin D and sunlight as our bodies have the amazing ability to manufacture our own vitamin D, termed D3 (in addition to dietary sources D2). It struck me on my run this morning looking at the snowdrops how there are similarities between us making our vitamin D3 and plants photosynthesising; we are both harvesting energy from the sun to power chemical reactions - which is pretty mind-blowing…
Although this sounds great - two different ways of getting vitamin D, this doesn’t come without some drawbacks. The D3 form needs sunlight of a particular wavelength, which in the UK is only present during the Spring and summer (April - September) and the dietary D2 sources are fairly limited.
How much do I need?
The most up-to-date recommendations are 10 µg’s per day or 400 IU.
Science factoid: A microgram is one millionth of a gram so it really is a tiny amount.
How can I get enough vitamin D then?
In terms of making your own “endogenous” vitamin D then you need to be in the sun between 11 am and 3 pm for 10-15 minutes. You don’t have to be “sunbathing” but your skin needs to be exposed.
[Remember this is only applicable during the months of April until September.]
I don’t normally advocate using supplements, but in this case I definitely recommend taking one daily ensuring it contains 10 µg during the autumn and winter as it is virtually impossible to get sufficient vitamin D from food alone. You can get supplements that are suitable for vegetarians and the Vegan Society also produces one.
What foods are good sources?
Unfortunately as I alluded to above, vitamin D is not the most abundant of vitamins and the richest sources (oily fish) don’t tend to be eaten by huge swathes of the population. That being said, it can be found elsewhere and I have compiled a list for you…
Any ideas/tips on how I can incorporate more of these vitamin D rich foods into my regular meal plans?
Personal disclaimer here: I 💓oily fish and try and eat it twice a week. I regularly buy smoked Pyrenean trout (you could substitute with smoked salmon) and pan fry it with some frozen peas, a squeeze of lemon juice, splash of vermouth, crème fraîche, dill and lots of black pepper. It goes really well with pasta and in fact I am having it for my dinner tonight!
Tinned red salmon mixed with mashed potato makes a great base for a fish cake.
Shitake mushrooms have higher vitamin D content and are great in stir frys (they have quite a meaty taste and texture).
KEY TAKE-HOME VITAMIN D MESSAGES:
References:
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