Vitamin D: Information, Testing and Dosing | Andrea Hughes Western Medical Herbalist, Functional Medicine, Est 2003

by health and nutrition advice journalist

Vitamin D has really hit the headlines in the last few months and quite rightly so as it is extremely important! Only last week a study was published giving very promising results in the treatment of Covid-19 with Vitamin D (1) and in fact that study prompted me to write more.

The purpose of this article is to give a brief outline of the role of Vitamin D in the body ( because that kind of stuff is always really interesting to write about) as well as giving you some practical information such as what your optimal levels should be, how to get tested, and how best to safely dose and which supplements are better to take and why!

Vitamin D insufficiency affects almost 50% of the population worldwide. An estimated 1 billion people worldwide, across all ethnicities and age groups, have a vitamin D deficiency (2)

I have been testing my patients levels and prescribing Vitamin D for about 10 years now and I remember clearly being told in a CPD lecture back then to “watch this space, because in about 5 years time everyone will be talking about Vitamin D” That pearl proved to be correct and I know that the lecturer spent many hours regularly trawling new studies published concerning Nutritional Medicine.

What exactly is Vitamin D and what does it do?

‘Vitamin’ D (also known as calcitriol, ergocalciferol, calcidiol and cholecalciferol) is a hormone, not a Vitamin! It is stored in the liver with other fat soluble Vitamins: A, E and K2.

A vitamin is an essential nutrient that our body must obtain from food and
a hormone is a regulatory substance produced in an organism and transported blood to stimulate specific cells or tissues into action. Vitamin D is required to absorb calcium from the gut into the bloodstream. Without vitamin D, only 10–15% of dietary calcium and about 60% of phosphorus is absorbed.

Our bodies mostly manufacture Vitamin D as you probably know – from Sunlight. It then undergoes a process of sulphation within the skin that is dependant on cholesterol and sulphate. Sulphate production is also stimulated by sunlight. The water soluble form of sulphated D3 can travel so much easier through the blood stream than the unsulphated forms.
Once Vitamin D is manufactured in the skin it undergoes a process of hydroxylation in both the liver and the kidneys, which changes it from an inert substance to a biologically active one: vitamin D 1,25(OH)2D

There are very few food sources of Vitamin D and it is unlikely that food alone will be enough to maintain replete levels. However, foods that contain some Vitamin D include mushrooms, oily fish, egg yolks and liver. More importantly the only unsulphated form of Vitamin D3 found in food is from raw milk.

Receptors for Vitamin D (VDR) are present in many tissues and cells and are highly expressed in the gut and studies show that Vitamin D can regulate gastrointestinal inflammation, with epidemiological studies showing that individuals with higher serum Vitamin D have a lower incidence of Inflammatory Bowel Disease, particularly Crohn’s disease. Vitamin D deficiency leads to dysbiosis of gut microbiome and reported to cause severe colitis. (3)

The role of Vitamin D in brain health has also been studied with deficiency linked with Depression and Alzheimers and a deficiency in expecting mothers linking to the development of autism (4) ( obviously this is not absolute as there are many contributory factors)

The protective effect of Vitamin D against Cancer prevention has also been studied suggesting that Vitamin D deficiency may account for several thousand premature deaths from colon, breast, ovarian, and prostate cancer annually. (5)

There are many studies showing deficiency in Vitamin D is associated with increased autoimmunity as well as an increased susceptibility to infection. In 2017 the BMJ published a meta-analysis concluding that Vitamin D supplementation was safe and it protected against acute respiratory tract infection overall.(6)

A new and exciting study was published August 2020 very relevant to the uncertain times we find ourselves in with the Coronavirus pandemic. The study showed patients hospitalised with Covid-19 infection significantly reduced their need for Intensive Care United admission when administered Vitamin D (1)

As well as observing many of the scientifically proven outcomes in my practice, I also commonly see patients suffering from SIBO ( Small Intestine Bacteria Overgrowth) who also test positively with a Vitamin D deficiency, this has also been noted by other Functional Medicine providers. As well as patients presenting with symptoms such as fatigue and hair loss who improve when their Vitamin D deficiency is addressed.

Testing, Supplementing and Dosing of Vitamin D

When I researched the guidelines from many different NHS trusts, I found the majority state that routine testing should not be undertaken. In 2016 the PHE stated adults and children over the age of one should have 10 micrograms (mcg) of Vitamin D every day, this advice was based on the governments scientific advisory committee (SCAN) (7) My question is once again, does once size fit all? Do we all need the same amount of Vitamin D supplementation and indeed do we all need to supplement?

During my time studying with the Institute of Functional Medicine, Vitamin D was indeed a hot topic and still is. The guidelines we were given stated that in in order to see us through the Winter months without the need for extra supplementation, optimal Vitamin D3 levels at the end of September should be at least 120nmol/L. Over the years I have seen many people with insufficiency and deficiency all year round! The reason we are told to test in September is because UVB rays are only available from the Sun from May to September.

The reference ranges for Vitamin D test can vary hugely between labs. I have seen most, but not all NHS labs give a range as follows:

<30 severely deficient
30-50 deficient
50-70 insufficient
70-200 replete
>200 danger of toxicity*

Birmingham Hospital lab as example states that anything over 50 is replete.

The lab that I refer my patients to has a reference range of 50-172 with anything under 50 as out of range and low. The measurement is in nmol/L

Again I follow the guidelines I was taught by the Institute of Functional Medicine where optimal levels in the Autumn are 120nmol/L. If I see a patient with a level of below 70nmol/L at anytime of the year I would consider prescribing a supplement, especially if that person has an autoimmune condition or a cancer diagnosis

Occasionally I see patients who are self medicating with large doses of Vitamin D over long periods of time. If this comes up in Consultation I always recommend a test to check the levels because you know, you can have too much of a good thing! Sustained high levels of Vitamin D above 275nmol/L have the potential to cause hypervitaminosis D which can result in hypercalcemia – elevated levels of calcium in the blood.

The mechanism of hypervitaminosis D is complex but very basically if the levels become so high that there isn’t any room left on the receptors or carrier proteins. (Remember Vitamin D is fat soluble and therefore cannot be excreted like a water soluble Vitamin) This can lead to elevated levels of “free” vitamin D in the body, which may travel inside cells and overwhelm the signalling processes affected by vitamin D, especially the calcium absorption from the gut. High blood Calcium can cause many symptoms including digestive disturbance and dizziness but more seriously can damage the kidneys and impact bone loss.

When, where and how to test for Vitamin D

The best time of year to test your Vitamin D levels is at the end of September because the UVB rays are gone and you will need to rely on your stores until May. Realistically I ask my patients to test anytime of year if they have not had a test for a number of years, if ever.

First I would say ask your G.P. They may well agree. Then ask for a copy of your results as you want to know your number.

There are a number of private blood tests you can choose from, I have a link to the lab that I recommend on my Medical Testing page and here it is again

You can choose a finger collection kit or a venous blood draw, if you don’t think you can get blood from your finger choose from one of the other options. If you live in Sussex I can refer you directly to a clinic for the blood draw. The lab also has it’s own clinics you can go to. The results are then sent directly to you.

For transparency: I receive a very small commission on any Vitamin D tests that are ordered via the above link.

Dosing and choosing a Vitamin D3 supplement.

So you have your test results now you need to choose your supplement and your dose.

Dosing is relatively straightforward and you can use this fabulous calculator to save you the time and brain effort of doing the maths
Calculating your Dose:

For example lets take ‘Sally’ a 39 year old female with a Vitamin D level of 54nmol/L tested early September. Sally has psoriasis ( an autoimmune disease) and is from Asian origin (darker skin needs more sunlight to gain Vitamin D) so really needs her levels to be around 120- 150nmol/L. She is currently not taking any Vitamin D. We put her details into the calculator and find that 50% of people with this level could achieve 120nmol/L within 3 months if they took a dose of 5000iu daily and 90% of people would achieve 120nmol/L on a daily dose of 7000iu.

I advised Sally to take 6000iu and test again in 3 months which she did and her result was near enough perfect so I then advised a maintenance dose of 2000iu daily with a 6 month check at which time we found her level to be maintained and so now we check annually in September.

Now you have your dose, what about your supplement?

Here we step into murky waters as not all Nutritional Supplements are made to the same standard.

I would generally say avoid Amazon as you cannot be sure of what you are buying even if the label looks good, and I would say avoid the branch chain high street health food shops. Some independent health food shops will carry some reasonable brands.

Vitamin D3 is fat soluble, so one in Vitamin E oil or similar is going to be be absorbed more effectively. Also remember the co-factors – the other fat soluble vitamins A, K2 and E. It is far easier to find a Vitamin D3 and K2 combination than one with A and E added. I currently I know of only one company that makes a product with D3, A, K2 and E. Sometimes I give a D3 and K2 with a separate (RDA) of Vitamin A and E.

Remember that Vitamin A is potentially toxic so make sure you’re not doubling up with a Multivitamin too. I recommend Practitioner only supplement brands to my patients, so if you are working with a Medical Herbalist, a Nutritionist or FM Practitioner do ask them to help you source. If not then I am happy to point you in the right direction to purchase but I don’t sell supplements. Most Practitioners get a discount on supplements and most are happy to share that discount with their clients and I certainly do that.

What about Magnesium?

It is also worth considering taking a Magnesium alongside the Vitamin D3. When Vitamin D undergoes hydroxylation in the liver & kidneys, Magnesium is a co-factor. (Actually Magnesium is a co-factor for many enzyme processes including methylation and conversion of Dopamine, but that’s another story…) If Vitamin D is not converted to it’s active form by this process then a person is at risk of increased Calcium levels rather than them being regulated by the Vitamin D. Food sources of magnesium include spinach, pumpkin seeds, almonds and cashews. However dietary sources are often not enough, partly due to the depleted soil in which food is now grown.

If you take too much magnesium it is likely it will be excreted and a sign of this is loose bowel movements.

Guidelines for daily intake of magnesium are as follows:
Females aged 19 – 64: 270mg
Males aged 19 – 64: 300mg

It’s never straightforward is it? There are many different forms of Magnesium to choose from. Most commonly people will self prescribe a Magnesium Citrate, this is ok, but because absorption of this form is via osmosis in the gut, it can be more laxative for some people. My favourite is Magnesium bisglycinate which is chelated with the amino acid glycine improving the solubility of magnesium and therefore the absorption and bioavailability (how easily the body can utilise it). Magnesium bisglycinate is also very calming for the brain and can help promote sleep.

My least favourite form of Magnesium is Magnesium Oxide, a waste of money because it is poorly absorbed, and don’t be fooled by the addition of Magnesium stearate to some nutritional supplements, it’s just an additive to help ingredients stay together in the supplement. Some people say it is dangerous others say it is harmless. I think the less added ingredients in a supplement, the better.

There are other ways of topping up Magnesium for example by taking Epsom Salt baths. Epsom Salt is Magnesium Sulphate. I advise 2 mugs of Epsom Salts to a bath as hot as you can take it and stay in for at least 20 minutes. There are various sprays, oils, bodybutters and shower gel’s also available to purchase.

Thank you for reading, I hope it was useful. Please share and spread the word via email or social media.

This content was originally published here.

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