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Vitamin A: Why We Should Pay More Attention to this Under-Appreciated Vitamin

Vitamin A is, like all of the fat-soluble vitamins (which include D, E and K), incredibly important.  Yet compared to Vitamin D (the sunshine vitamin, the pro-hormone and the one that we always hear about – and that even I wrote a whole article about here) Vitamin A is seldom discussed in mainstream circles.  Whilst your practitioners will recommend it, your GP is unlikely to.  And whilst it doesn’t have the links to ‘all cause mortality’ that have been demonstrated with Vitamin D, it is one of those vitamins without which our health seriously starts to decline.


What Does Vitamin A Do?


Perhaps the most famous function of Vitamin A is its contribution to good eyesight.  Vitamin A can be made from betacarotene in carrots.  This is what led to the (almost plausible) military explanation that “carrots help you see in the dark”.  The British World War II campaign which promoted this idea (to conceal from the Germans that they had revolutionary, top-secret radar technology) took for granted that the Germans weren’t great on biology, however.  Because whilst the mechanism or deriving Vitamin A from beta-carotene in carrots is sound, in practice there are many who lack sufficient enzymes to make the conversion from plant beta-carotene to utilisable Vitamin A.


A slight sidebar here: those who genuinely thrive, sometimes even becoming competitive athletes, on vegan diets are often considered outliers to the norm.  This is because the vegan diet is deficient in several vital nutrients.  Whilst these can be supplemented, if judicious attention is paid, there are still those for whom veganism is simply a raging success.  It is often postulated that these outliers (or ‘mutant superheroes’ as one recent client of mine called them) potentially have genetics which supply them with more of the enzymes which help the conversion of plant compounds to useable minerals.  If you read my last article which touched on Omega-3 contents and Iron content of meats and fish vs. plants and algae you will recognise how typically our conversions of plant compounds into useable forms of sustenance for humans is woefully inefficient.  Those who have the genes which make this easier are those who thrive on diets which exclude more readily bioavailable nutrition.


But back to Vitamin A:

Despite the fact that Vitamin A does NOT help you see in the dark, the grain of truth in the carrot myth is that Vitamin A is actually good for eyesight – along with being good for healthy bones.

In my practice Vitamin A is also vital for those with the health issues I see most frequently: often gut-related/digestive distress and autoimmunity.  Vitamin A is really key in all barrier tissues, including gut mucosa/lining but also playing key roles in skin health, lung health, sinuses.  It’s also believed to be important in connective tissue – though Vitamins C, D and E are also critical here.  Barrier tissues are what keep us inside us – and everything else outside of us. Breaching barrier tissues is one of the lead dominos in an up-regulated immune response, the consequences of which can cascade and become catastrophic.

Vitamin A has been shown to ‘activate’ certain receptors in the body known as Retinoid X Receptors and Retinoic Acid Receptors. (RXR and RAR).  For the sake of simplicity I’m not going to go into the mechanisms too much, but suffice it to say that the activation of RXR is fundamental to the activation of two further ‘receptors’: VDR (the Vitamin D Receptor) and THR (thyroid hormone receptor).

If you have read anything at all about Vitamin D you will know how crucial it is to the body.  Well, in order to play its role the VDR receptors must be activated.  If you know anything about thyroid health you will know how crucial thyroid hormones are to everything from metabolism to temperature regulation, body fat regulation, hair and nail strength, energy levels and more.  Basically having the VDR and THR activated is the foundational precursor to the correct functioning of these systems.  Therefore Vitamin A could be said to pave the way for optimal functioning of the entire body.

Vitamin A is additionally used as a building block for some hormones.  And, for real nerdy, complicated reasons I won’t explain here the RXR and RAR mentioned above also play a role in DNA binding proteins… which basically means that genetic expression, i.e. what regulates which traits are expressed or dormant from within our DNA, can be altered by a lack of Vitamin A.  Whilst it will always be the Vitamin D which gets the glory (it does a lot of the actual ‘work’, without the Vitamin A activation of RXR the Vitamin D literally cannot do its job.

I’ve already touched on it briefly, but my patient population is mostly autoimmune or dealing with immune dysregulation, Vitamin A plays an important role in the regulation of the adaptive immune system.  This is the part of our defence mechanism that ‘learns’ about what is an enemy based on introductions to that substance.  Our adaptive immune system is designed to flare in response to a new threat and begin the elimination of it whilst simultaneously creating antibodies to ‘remember’ that threat.  Once the job of immune attack is no longer needed because the threat has been neutralised, the immune system has self-regulatory ‘off-switches’.

If you know anything about the hypothesised ‘causes’ of autoimmunity you will appreciate that one factor of autoimmune conditions’ development could revolve around the inability for this ‘off-switch’ to be turned off.  Perpetual immune reactions equals permanent inflammation – and all of the consequences that accompany this.  Vitamin A is part of the mechanism which decreases the level of immune cytokines.  These are not the antibodies, these are the more blunt ‘killer’ cells which are sent out to attack anything that is a potential threat.  The quelling of this cytokine response is fundamental to minimising an out of control immune activation – which potentiates the development of autoimmunity.

And lastly, in pregnancy, Vitamin A is essential for the development of the foetus’ kidneys and also for the growth of the neural pathways between the brain and sensory organs.  Vitamin A deficiency has even been associated with pregnancy loss when the formation of these vital components of a viable foetus are not completed effectively.

So you can see (pun intended) that Vitamin A is a functional backbone to much of our human biology and processes.


But What About Vitamin A Toxicity?!


I mentioned earlier that Vitamin A gets much less mainstream media attention than the superhero Vitamin D.  That is, of course, except when they want to sensationalise the downsides…

You may or may not have read about this, but Vitamin A can be toxic.  When you eat it in the form of Polar Bear’s liver, that is.

In my article on Liver Detoxes you will have read that I heartily endorse the consumption of liver.  That is because, gram for gram, it is by far the richest source of nutrition we can find – and part of that nutrition is Vitamin A.

But of course, as with every vitamin, mineral, substance and foodstuff, you can seriously over-consume Vitamin A.  Whilst many ‘over-consumption’ quotas of foodstuffs/nutrients would have to come from artificially supplementing with the nutrient in question, with Vitamin A you actually can overdose on it through whole-food consumption.


The only issue is that the whole-food sources you’d have to consume to obtain this quantity of Vitamin A are foods that you, realistically speaking, would never eat.


You need to be going some to over-consume Vitamin A – even on the most carnivorous of Paleo diets.  By “going some”, I mean eating any bear’s liver, though especially polar bear liver.

The livers of bears and polar bears are really rich in Vitamin A, coming in at roughly 300,000-800,000 iUs (international units)!  The Recommended Daily Allowance (RDA) for liver is 3000 iUs for adult males and 2300 iUs for adult females (with pregnant and lactating women needing a touch more).

Bear’s liver, therefore, is at least 100 times the RDA.  However, I don’t know about you but my butcher doesn’t tend to get Polar Bear Liver in to sell me…

In a more sane world, and on normal dietary consumption, the main source of Vitamin A would be Beef Liver – where a 3oz serving is 22,000 iUs of Vitamin A.  That’s a lot, you might say – and still well over the RDA.  However, we rarely have liver every day of the week, and often not in the 3oz quantity (that’s nearly 100grams).  This means that when this is averaged out over the course of weeks and months the Vitamin A we get from beef liver is exceptionally good for us, and at high quantities – but it’s certainly not toxic.

I mentioned that Vitamin A was vital to pregnant females and the development of the unborn child, with deficiencies leading to defects and sometimes miscarriage.  However, you may also have heard that excess Vitamin A is problematic in pregnancy – so what side of this is true?

Here we track back to the idea that supra physiological doses of vitamins are normally obtained through supplementation.  In one isolated study it was the use of synthetic Vitamin A at high levels which were shown to lead to neural tube defects and birth deformities in pregnant women.  However, recent studies have failed to replicate these results.

This is thought to be to do with the fact that, as outlined above, Vitamin A and Vitamin D appear to work in conjunction in the body.  They do this both collaboratively but also competitively.  Supplementing with Vitamin A when the person has plentiful Vitamin D is one thing.  When supplementing with Vitamin A when there is a Vitamin D deficiency has a very different effect.  When there is not enough Vitamin D compared with Vitamin A the regulatory processes outlined above become distorted and Vitamin A is experienced to be in excess – which can produce toxic and negative effects.

All of the fat soluble Vitamins work in concert – with Vitamin K supporting Vitamin D, with all the varieties of Vitamin E working synchronistically and with Vitamin A being a lead domino in pathways that must have the other fat soluble vitamins present in order to work effectively.  This is why any effective practitioner will rarely recommend supplementing with these fat soluble vitamins in isolation.  The possible exceptions are when Vitamin D is exceedingly low (though typically K is given alongside).

And yet the really effective strategy for Vitamin A supplementation has nothing to do with supplements and everything to do with real foods.  The reason for this is because whole food sources of fat soluble vitamins are so fundamentally well ‘designed’ (by nature) that these vitamins are rarely isolated and are all found together in perfect ratios to one another.

Take another fat soluble vitamin – Vitamin E.  This is another Vitamin that gets a bad press for toxicity.  However, in truth the many forms of Vitamin E known as varying ‘tocopherols’ must be consumed in a balanced fashion.  Over consumption of one specific tocopherol will result in negative outcomes (potentially even toxicity at very high and imbalanced levels).

This brings us to the trendy, hippy ‘superfood’: the Avocado.  In an avocado, all forms of tocopherol are present in the perfect ratio for your body.  Eating Vitamin E in the context of the whole avocado, or consuming Vitamin A in the context of liver and other offal, or getting your Vitamin D in the context of getting out in the sunshine throughout all times of the day builds balance into your nutrient levels through the virtue of these vitamins existing in a balanced fashion in nature.

When it comes to Vitamin A and D being competitive and needed in the right proportions for our physiology, you will find that Vitamin A and Vitamin D come nicely packaged inside the same food.


But what foods contain Vitamin A in such perfect proportions?

Well, the animal form of Vitamin A (not the plant form which are carotenoids as mentioned above) is found in abundance in liver, seafood, egg yolks and grass-fed dairy products.  What a coincidence, the highest food sources of Vitamin D are oily fish, liver, egg yolks and grass-fed dairy products.  Anyone would think nature knew what it was doing…?

So yes, if you want bang for your buck, perfectly proportioned, highly nutritious foods rich in Vitamin A and D we really are back on the recommendation of good quality animal produce, wild-caught oily fish and, yes, liver.  Perhaps not Polar Bear liver… but definitely the more domesticated animals such as beef, chicken, pork, lamb and also some fish livers if you can get them.

And if you can’t stomach liver there are many options.  Hiding it in foods such as homemade burgers/sausages, bolognese, chilli, shepherd’s/cottage pie, casseroles etc. is always an option.  And then there’s pate, so rich in herbs and flavours that the rich, iron taste of liver is hidden… a quick google of “Liver Recipes” yields much inspiration and ways to get this nutrient powerhouse into your life.

A last quick word on the oft-forgotten Vitamin K:

I didn’t mention Vitamin K very much in this article.  I would write about it, but the work I contribute would pale in comparison to the esteemed and fabulously engaging Dr Chris Masterjohn PhD.  If you’re at all interested in the complex physiological role of what we used to call “nutrient X”, his exceptional resource on everything humanly possible to know about Vitamin K can be found here… (be warned… very long, very science-y, very interesting… you may lose hours of your life to being fascinated by this resource).


This article originally appeared on the website of our Functional Medicine Consultant Founder, Victoria Fenton


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