About the author : victoriafenton

If you saw any news reports this morning you will have heard the latest media-reported evidence about the benefits of supplementing with Vitamin D: this time in the context of preventing coughs, colds and flu for over 3 million people per year.
Many viewer testimonials were read out with people saying “I’ve been taking Vitamin D for years and still have colds and flu”.  Still more were read out saying “I’ve been taking Vitamin D for years and never get sick!”.
All of which made me mad – particularly when the suggestion was that it would be healthy to put Vitamin D supplementation into foods to fortify them.
This makes me angry for many reasons – so I thought I’d take to my blog to explain.

Some Biochemical Roles of Vitamin D

Vitamin D is actually a steroid hormone which regulates the expression of over 1000 different genes within the body.  This means that it’s more appropriate to view this as a hormone than a vitamin – so super-powerful and very important.  The studies discussed on the news today were almost myopic in the fact that they focussed on colds and flu.  In no way would I perceive this as a key role of Vitamin D in the body, but it is one of them.
We synthesise Vitamin D from UVB radiation (that means from the sun), but sunscreen, skin pigmentation and aged skin can slow down synthesis and body fat will affect the bioavailability of Vitamin D because it is fat soluble so will be stored there.
Itemising the full list of the roles of Vitamin D would take far too long – and more than that, we are still discovering its full regulating capacities within human physiology.
Vitamin D can regulate the ageing process through its role in preserving little tails called “telomeres” on the end of our DNA.  These little tails essentially get shorter every time cells are replicated (in the producing of new cells).  The shortening telomeres are thought to be the ‘reason’ we are ageing – because once a telomere disappears, that cell enters a state of programmed death.  Vitamin D has anti-inflammatory properties, and these are thought to be the mechanism by which this hormone actually regulates lifespan.
But you can’t catch a common cold from a shortening telomere.

Gut Health, Inflammation and The Brain

One of my key areas of interest regarding Vitamin D deficiency is its role in gut health.  This takes some scientific explanation, but bear with me because the conclusions (and what we can extrapolate) are fascinating.
Vitamin D is a key regulator of the serotonin pathway.  Dr Rhonda Patrick has done some phenomenal work in this area, with published research demonstrating that Vitamin D has a profound effect on a gene that encodes for the production of an enzyme called Tryptophan Hydroxylase (TPH).
Trying to keep this as short as possible: the TPH enzyme is the rate-limiting step (i.e. slows it down and speeds it up) of converting L-tryptophan to serotonin.  Serotonin is well known for its role in mood, happiness etc. but it does so much more.
There are actually two separate TPH genes/enzymes in our body, in two different places.  TPH1 is predominantly found in the gut, TPH2 is found in the brain.
In the brain, THP2 converts L-Tryptophan to the serotonin used in the brain as a mental neurotransmitter which regulates mental functions as diverse as mood and happiness, but also impulse control, expression and regulation.
In the gut, serotonin plays an important role in the aggregation of blood platelets – i.e. blood clotting and wound healing.  This serotonin DOES NOT cross the blood-brain barrier itself (as some blogs on the net would have you believe), but works solely in the gut region.  It is vital for the health of the GI tract, in that too much serotonin causes gut inflammation.
Vitamin D is quirky in that it turns ON the TPH2 gene (brain) and turns OFF the TPH1 gene (gut).  i.e. Vitamin D causes MORE serotonin to be made in the brain (the happy neurotransmitter) and causes LESS serotonin to be made locally in the gut (where an excess causes inflammation).

This thereby means that too little Vitamin D (i.e. the deficiencies mentioned in today’s headlines) causes a LACK of brain serotonin and an EXCESS of gut serotonin – which equals gut inflammation and low neurotransmitter serotonin for good mood and impulse control.

And anyone who knows my work knows that gut inflammation can be the precursor to every illness in the body – from the colds and flu discussed by today’s headlines (caused by reduced immunity after inflammation is present) to autoimmune conditions, joint pain issues and chronic fatigue syndromes.
And the Vitamin D-serotonin-brain link deepens because in the womb serotonin determines brain development and coordinates neural pathways and the construction of the regions of the brain.  It’s a deductive leap, and requires other genetic factors regarding serotonin to be in play, but realistically a Vitamin D deficiency in a pregnant mother may cause delayed or stunted brain development in her foetus.  This has been linked to autistic spectrum disorders, within which gut serotonin has been studied and shown to be notably high.  Gut health issues are extremely common in those with ADHD and Autistic Spectrum Disorders.
So for this dual reason – brain development, mood, serotonin AND gut-serotonin lowering, Vitamin D is massively important.

Vitamin D As Effect, Not Cause

Beyond these more niche and focused findings, studies have shown that optimal Vitamin D levels reduce the risk of all-cause mortality.  But causality is very hard to prove with nutrient levels.  It is tough to state whether inflammation and oxidative stress (two states wherein the body is struggling and producing excess inflammatory markers, cytokines, reactive oxygen species and, essentially, cell damage) are correlated with low Vitamin D, are caused by low Vitamin D, or whether these states themselves cause low Vitamin D.
Put simply – we realise that the optimal levels for Vitamin D are between 30-60 ng/ml, but other than sun exposure and supplementation there are many factors which can cause (and be associated with) either an inability to synthesise Vitamin D, or rapid turnover of Vitamin D.
It is unequivocal that optimal Vitamin D levels are correlated with good health and positive health outcomes.  However, how much the Vitamin D is a leading cause for those outcomes is highly speculative.


And this is where the idea of supplementing or fortifying with Vitamin D can come under great scrutiny.  There are many things that affect an individual’s ability to absorb, synthesise and use Vitamin D: some genetic, some metabolic, some nutritional and some lifestyle.
This may perhaps be one of the reasons why there were such different stories reported by viewers of the TV shows and news this morning: the dosage of Vitamin D with which they were supplementing may have been vastly different.
There is a sweet spot for Vitamin D levels, as shown by the study above, at between 30-60 ng/ml.
So, just assuming someone is Vitamin D deficient, how can we boost up their levels to be within that optimal range?
Studies have shown that 1000 International Units (IUs) per day will raise blood levels by 5ng/ml.  Yes – 1000 = 5.  That means that 400 IUs (typically the dosage in GP’s supplements) will do practically nothing to the overall Vitamin D levels in the blood.  If we are to supplement for those deficient, we need to be taking massive doses to make any observable difference.
I have already alluded to the genetics, and there is a certain polymorphism (SNP) which can slow down the conversion of D3 to 25 Hydroxy D3 (and then to 1, 25 Hydroxy D3), the necessary steps to take sunshine from the skin into the useable steroid forms.  For those with a SNP in CYP2R1 gene, this process is slowed.  This means that the suggestion that supplementing with fortified food would prove useful is nonsense, as for these individuals the dosage would be so supraphysiological that it would never pass state approval for nationwide fortification.
Which brings me onto the next concern of mine, after the headlines this morning.

The Perils of Fortification

One of the biggest concerns about the prospect of fortification relates to the above concept of dosage.  It is clear to me that for those truly deficient in Vitamin D there is a requirement for supplementation at the level of thousands of IUs per day.  Fortification, as it will be consumed by everybody, is unlikely to be at this level because it would be both expensive and unwise to supplement the general population with such high levels (that’s if it’s even possible, and frankenfoods are not my area of specialty!)
This is a big deal for the psychology of supplementation.  If we believe we are being supplemented with Vitamin D through fortified foods we will not think there is a need to take a supplement.  We could, for years, be taking roughly 400IUs of Vitamin D (a common starter dose) every once in awhile when we eat that fortified food and feel like we’re doing enough.  As you can tell from the list above, this is nowhere near enough to boost Vitamin D levels for anyone who is deficient.  This means that because we think we are doing the right thing, we will actually never be doing the best for our bodies.
So whilst fortifying foods may keep Vitamin D levels steady in those who are already doing OK, it will not be enough to tip the balance for those who really have deficiencies.  And what about foods plentiful in Vitamin D already, surely the best way to ‘fortify’ the diet with Vitamin D is to encourage natural consumption of such foods – of which the most beneficial would be fish.
Even if we go down the fortification route, there is a big question of ‘how’?  Firstly, Vitamin D is a fat-soluble vitamin… which means that it is absorbed through a fat source, and that’s why supplements are often oil-based capsules.  How exactly are they supposed to put into food – must it be put in oil or fats?  And so I ask again, why don’t we just eat oily fish?
Or should we just trust that every single person is taking in the right quantity of fats within their diet and sufficient cholesterol (yes, really) to make the right conversions if we fortify something like bread with Vitamin D?  It’s all a bit like nonsense, to my mind.  And such a risk…
Our most famous attempt at fortification was when the UK government put folic acid into bread to help pregnant women prevent neural tube defects (amongst a few other things).  Put simply, folic acid is not folate (the human-produced version of this nutrient, or the version of the vitamin present in leafy greens, i.e. real foods) and therefore folic acid in bread doesn’t work identically in the body.
This means that some pregnant women will not benefit at all from this fortification (lacking the right nutrients for conversion and usage), but additionally the billions of people consuming this fortified bread who don’t need the folic acid (or extra folate for that matter) are having to use their liver detoxification and biochemical metabolism processes to eliminate this out of their system.

In short – generalised fortification is great for some, pointless for others and perilous for the rest.  I am very against mass-dosing with supplements, benign as they may seem on the surface.  Functional Medicine is INDIVIDUALISED medicine for this reason.

What also worries me about all of this is that the group who conducted the analysis argued for the inclusion of Vitamin D in food immediately.  However, Public Health England (PHE) disagreed, stating that there was insufficient evidence.
This is a bonkers statement, or maybe just bonkers media reporting (which is equally probable).  This statement gives the impression that PHE thinks there is insufficient evidence for the role and benefits of Vitamin D.  Which is ludicrous.  And whilst this may not be the PHE’s contention at all – they may just think there’s insufficient evidence for fortification, or that the prevention of coughs and colds is not beneficial enough to warrant mass-scale dosing of the population.  But a statement saying there’s insufficient evidence certainly leaves the reader confused.

So Should You Take Vitamin D?

So after the science, the nonsense about fortification and the question about where the evidence lies and what is healthy and not, what should you (or me) the individual do?
The answer, as always, lies in personalisation.  My recommendation is to get your levels tested, and if you’re low (below 30 ng/ml) take a supplement which will make a significant and dose-appropriate difference to improving your levels.  Work with a practitioner if you want to, but you can do this alone.
That said – please don’t see this as curative.
I have never clinically witnessed someone’s health fortunes miraculously turn around after supplementing with Vitamin D, even at the right dosage.  The reason for this may lie in the “cause or effect” section above.  But it might also lie within the fact that Vitamin D is an essential pro-hormone and pre-cursor to a lot of effects.  It performs essential activating and suppressing roles as a preventative for illnesses and as a baseline of nutrition which ensures that all physiological functions are working correctly.
That means that illness is likely concomitant with low Vitamin D, in that when a system is undermined it is likely that Vitamin D is also deficient.  This doesn’t automatically guarantee that health outcomes are going to be reversed by supplementing with this vitamin.
From all the studies I can read I always come to the conclusion that whilst lack of Vitamin D is unlikely to be the sole cause of illness, it is likely that when someone has Vitamin D deficiency they are much more vulnerable to other physiological systems going wrong, whether this is catching the common cold or something more serious.
For this reason I believe that leaving oneself Vitamin D deficient is like leaving the door open and waiting to be robbed.  It is a relatively easy supplement to obtain and take, and in the UK climate it is pretty much essential that we boost our levels of Vitamin D however we can.  And whilst taking Vitamin D supplementation might not drastically alter your health, it might just be an important baseline supplement which ensures that your health isn’t drastically affected by something else.
If you’d like me to look into your Vitamin D for you, I can – but seriously I’d recommend going to the GP instead if you’re concerned.  DO NOT book an emergency appointment, just request for them to check when you’re next using their services.  And if you think you could boost your levels – eat fish, take a fat-based supplement at the right level… oh yes, and get some sunshine whenever you can!

Leave A Comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.