Could your Vitamin D supplement be the cause of your headaches, acid reflux and constipation, and what can we learn from the cast of FRIENDS?

Does this sound like you? You read an article/blog about the benefits of ‘XYZ supplement.’ You feel like ‘yeah, I have those symptoms,’ or maybe you don’t yet but ‘there is no harm in trying them anyway, right?’ and you make your purchase.

Your new supplements arrive, and you start taking them which you think makes a positive difference. So, you continue to take them for…… how long? Until the bottle runs out?  Ah, but you have them on subscription, so there is another bottle popping through the letterbox! Until you read another article dispelling the benefits – maybe!?

Well, for most, they carry on taking them FOREVER.

If this resonates with you, then you are not alone. I always ask my clients to tell me why they are taking ‘XYZ supplement,’ and if it has helped? Invariably the answer is ‘I can’t remember why,’ or ‘I read somewhere that it helps.’ If you don’t know why you are taking something, how can you decide when you no longer need it?

Not only could you be wasting your money, but this scattergun approach to supplementation might be doing more harm than good.

Vitamin D

An excellent example of this at the moment is with Vitamin D. Vitamin D is very much the supplement du jour, and there is a lot of merit in this.  There can be long periods of time in the UK when the sunshine can be hard to find, (although that is hard to imagine today). However, this does not mean that EVERYONE in the UK needs to supplement Vitamin D, all the time!

If you are not deficient, you don’t need to supplement it! If you are lacking, you only need to increase until you are within an optimal range. Not indefinitely and not at super-high doses. With supplementation the adage ‘the dose makes the poison’ always applies.

The body is a complex network of biological processes, and nutrients do not work alone, they have friends known as co-factors. Vitamin D is no exception, and over-supplementation can cause you problems.

Let’s explore more – what is Vitamin D, why do we need it?

We call it a vitamin, but it is actually a steroid hormone. It is made by our bodies from our skin being exposed to sunlight.  We can also get small amounts from the food we eat. As I said, it is a steroid hormone, and as such, it controls 100’s of different genetic processes. It actually regulates the receptors for other steroid hormones (such as sex hormones and adrenals).

Gut health

It plays an essential role in gastrointestinal health by strengthening the tight junctions in the gut which helps to prevent the increasingly prevalent condition, leaky gut.


It is also an immune modulator. Optimal levels are essential for immune-mediated conditions, such as rheumatoid arthritis, allergies, and so on. But note, I say optimally. Too much Vitamin D can actually suppress one part of your immune system rather than allowing it to work in balance, the way our body is intended to.


But Vitamin D is probably best known for its role in bone health and Calcium regulation. It is the master controller of our plasma (blood) levels of Calcium (and Phosphorous). If serum calcium is low, then Vitamin D will sense this. It will signal for us to increase the amount of Calcium we absorb from our food and reduce the amount we pee out.

This elegant mechanism, when working well, spares us from dipping into our Calcium reserves within our bones. If blood calcium levels fall, Vitamin D will have no option other than to liberate Calcium from our bones into the bloodstream to bring back homeostasis.

Remember, nutrients work in concert with each other, and there is another party in all this, and that is Magnesium.


Put simply, Magnesium facilitates Calcium and Vitamin D production. It is used in over 300 intra-cellular processes within our body, most of which promote relaxation. Unfortunately, many of us are not meeting our daily Magnesium requirement. In part, this is due to the erosion of our topsoil and the depletion of minerals in the soil in which our food is grown.

Magnesium is a co-factor required for liver and kidney enzymes that convert Vitamin D to Calcitriol and also for the thyroid hormone Calcitonin. Magnesium gives itself willingly and will go where the highest demand is – but supply is not infinite.  We can create a functional deficiency by putting excess demand on it. When Magnesium levels are depleted, another biological process will have to suffer.


One of these is gut motility, which leads to problems such as constipation. Magnesium draws water to the colon and softens stools. It also encourages peristaltic action, which is a series of contractions that move food through our intestines. If there is insufficient Magnesium, it will make peristalsis sluggish. Furthermore, Calcium and Magnesium compete with each other for absorption into the intestine. Magnesium passes more readily; however, if there is too much Calcium, then intake may be reduced for both. If you are experiencing symptoms such as acid reflux, muscle cramps, headaches, and (as discussed) constipation, it could be that your Vitamin D supplement is driving down Magnesium levels.

I always like to ensure that my clients’ Magnesium levels are optimal before dosing Vitamin D.

What can we learn from the series FRIENDS

The hugely popular TV series FRIENDS was so successful because of the fantastic characters and the relationship and chemistry between them.  Vitamins and minerals operate in much the same way. If you take one in isolation it doesn’t work in the way you might intend it too.  Need I remind you of the Matt LeBlanc spinoff show, ‘Joey’?!

Using the three girls in FRIENDS as an example illustrates this.

Just imagine Rachel Green is Vitamin D – the protagonist of the cast, (she definitely had the most headlines off the show). She flourished with the support of her friends but was never allowed to get too big for her boots.

Monica Geller (Bing), I consider as Calcium, strong-willed, reliable, and the backbone of the group. She gets the job done. She is related to Ross, (who is Vitamin K), the other nutrient so essential to bone health.

Then we have Pheobe Buffay, who I liken to Magnesium. She is incredibly open and spontaneous, freely sprinkling her crazy magic on everyone she meets.  Life would be duller without her.

Each one plays such an important role.  They support each other’s strengths and balance out each other’s weaknesses. You can guarantee they are always there for each other.

Enter the supporting cast, the boys (only joking)

Another important interplay is between the other fat-soluble Vitamins – K, E, and A. If we continue with the FRIENDS analogy it also works for the guys in the show.

Vitamin K

Ross Geller is Vitamin K works synergistically with Vitamin D (Rachel). It helps direct Calcium (Monica) to where it is needed (the bones) and away from the arteries. Ross was a paleontologist (they are interested in bones)! I always felt he made Rachel a better version of herself. They were meant to be together, ‘his her lobster’!

Vitamin A

Joey Tribbiani, easy on the eye and always thinking of his stomach. Joey is Vitamin A. He was in an uncomfortable trio with Ross (Vitamin K) and Rachel (Vitamin D). When he was friends with Rachel, it worked well. Then they started to have intense feelings for each other – their relationship was out of balance and it didn’t feel right.

Vitamin A is crucial for eye health and gut immune mucosal. It shares a receptor with Vitamin D in the nucleus of a cell. If you supplement too much Vitamin D, it will grab the receptors and leave no room for Vitamin A and vice versa.

I would not be at all surprised if I start to see more clients showing symptoms of a functional deficiency in Vitamin A in the future.

It is also important to note that there are areas of the population that can’t convert the Beta Carotene they get from food into formed Vitamin A. This is particularly apparent in those with Type II Diabetes and Hypothyroidism.

Vitamin E

Finally, Chandler Bing is Vitamin E. He has bad habits like smoking and was more flawed than the others. He struggled to find a girlfriend for ages and had periods of self-destruction.

Vitamin E is a powerful antioxidant (great for your skin) but can go awry if it’s single for too long and become a pro-oxidant. It bounds around, as my lecturer once said “like a drunk friend on Tinder,” desperately trying to find someone to pair up with and become more stable, if not it remains a free-radical causing mayhem. Monica saved him.

Better together

Put the whole cast together, and the synergy is unbreakable. Try and separate them, make one more important than the other, and it will not work. Our body is precisely the same – it has been fine-tuning this chemistry since time began.

What can you do then?

There we have it, a cautionary tale of not mega-dosing on individual vitamins. This is just a small example of the implication of taking a reductionist approach to supplementation.

Yes, give the body what is missing.

Yes, take away what it doesn’t need.

But always remember it knows better, it is continually working to restore homeostasis.

Always try to find the ‘Why’. Ask yourself, why am I deficient?

  • Are you not getting enough sun on your skin?
  • When you are outside, do you always use a sunblock?
  • Are you not getting enough Vitamin D from your diet?
  • If you are eating a diet, plentiful in Vitamin D rich foods but your blood test is still showing low levels, then what is going on? Is there a problem with your digestive tract? Digestion is one thing, but we need to be able to absorb nutrients so they can get into the bloodstream before they can travel to their target destination.
  • Are you carrying extra weight around your tummy (known as adipose tissue), if so these fat cells could be stealing your Vitamin D?
  • It’s a fat-soluble vitamin, can you actually breakdown fat? If it can’t, you won’t make it too your blood. You might have had your gallbladder removed, or you don’t have optimal bile flow, perhaps you need pancreatic enzymes.
  • Are your liver or kidneys functioning well, can you detoxify steroid hormones?

And so on……. I hope you get my point that there could be one of many avenues that need exploring.

So, what should you do?

My advice is simple, have a blood test to see what your Vitamin D levels are, and take it from there.

If you do need to supplement, then do so, low and slow.

Then you re-test!