Why is Vitamin D so crucial right now?
”One of the primary benefits of sunlight is its ability to stimulate vitamin D production”
― Chris Kresser, Functional Doctor
If you do one thing for your health besides eating well and exercising, it MUST be getting more vitamin D - through sun or supplements. Vitamin D deficiency, affecting 75% of UK citizens, is mostly due to inadequate sun exposure because of climate, lifestyle and concerns about skin cancer. Fixing this now is important for protecting yourself against COVID-19 as the world opens up after the pandemic. But it’s also badly needed to prevent and treat our chronic disease epidemic - heart disease, cancer, diabetes, depression, obesity, and autoimmune disease. One vitamin D expert stated. "We won't know the true burden of chronic disease until we eradicate vitamin D deficiency."
Many physicians are responding to recent research linking a variety of disease states and general wellness to vitamin D levels. The COVID-19 pandemic has thankfully brought vitamin D into sharper focus. Recently, researchers in Italy published new meta-analyses of 43 observational studies examining the relationship between vitamin D and COVID-19. The results indicate that low levels of vitamin D are strongly associated with a higher risk of infection, hospitalisation, ventilator use and death from COVID-19. (1, 2)
Michael F. Holick, MD, PhD, professor of medicine, physiology and biophysics at Boston University School of Medicine, recently published a study which found that adequate vitamin D can reduce the risk of catching coronavirus by 54 percent. Holick believes that being vitamin D-sufficient helps to fight the consequences of being infected not only with the coronavirus but also by other viruses causing upper respiratory tract illnesses, including flu. “Because vitamin D deficiency and insufficiency is so widespread in children and adults in the United States and worldwide, especially in the winter months, it is prudent for everyone to take a vitamin D supplement to reduce risk of being infected and having complications from COVID-19.”
What does Vitamin D do for us?
Vitamin D is not actually a vitamin, but a hormone that is largely produced in the skin when exposed to ultraviolet radiation. There are receptors on nearly every cell in your body which, when bound to vitamin D, controls the expression of more than 200 genes. But that is not all.
It is critical to the proper functioning of your immune system, fighting infection by stimulating the cellular immune response and by activating the body’s defense mechanisms to destroy viruses and bacteria. It isn’t a coincidence that most respiratory infections, including seasonal flu, are much more common in winter months when days are short and dark and vitamin D levels tend to be lower.
It is essential for bone health by facilitating calcium and phosphorus absorption into the bloodstream from food in the intestine, (low vitamin D levels reduce the absorption of calcium by up to 90%). It enables proper mineralization of bone and protects against osteoporosis, rickets and fracture. (3)
It also has a little-known role in regulating insulin secretion and sensitivity and in balancing blood sugar. (4) It also regulates cell growth and neuromuscular function.
Why does it matter?
Deficiency of this fat-soluble vitamin is a real cause for concern. It is not just associated with respiratory tract viral infections, but also with increased risk of dementia, Type 2 diabetes, high blood pressure, at least 17 different types of cancer, autoimmune disease, stroke and heart attacks (5).
Deficiency is also associated with numerous autoimmune diseases in the scientific literature, but specifically with autoimmune thyroid disease (Hashimoto’s), a disorder in which your immune system creates antibodies that damage your thyroid gland.
In a 2007 meta-analysis of 18 randomised controlled trials, conducted mostly in older people, the authors reported a significant reduction in all-cause mortality, in those taking vitamin D supplements. (6)
How many of us are deficient?
Largely as a result of our modern indoor lifestyle limiting our exposure to the sun (which is limited in the UK anyway), about 75% of the UK population is deficient in this critical vitamin. This is a real cause for concern. The problem is that we can only get a small amount from diet. Supplementation is the only other option. Sensible vitamin D supplementation has a long track record, and side effects are minimal.
You are most likely to be deficient if:
there is low sunlight either because it’s winter or you because you are stuck in an office and don’t get outside much
if you weigh more than maybe you should – body-fat soaks it up fast. Obesity is known to significantly impair the production of vitamin D when the skin is exposed to UVB (Ultraviolet B rays). (7)
if you are super fit (muscles use it up)
if you are pregnant (Vit D drops dramatically)
if you have a leaky or inflamed gut: since vitamin D is absorbed in the small intestine, this condition reduces it’s absorption
if you are dark-skinned (you need up to 10 times more sun than pale-skinned people to produce the same amount of D as a result of the increased amount of melanin in your skin)
if you are elderly – age reduces the amount your skin can produce from sunlight. Further, the elderly tend not go to outside so much and when they do, they cover their skin with clothing.
if you are vegan, as you are likely to be avoiding eggs, meat and fish
if you are coeliac or have lactose intolerance, for this results in an inability to absorb D from the gut.
if you are not eating enough fat – or not digesting fat properly – as vitamin D is a fat-soluble vitamin which means it needs fat to be absorbed.
Where can I get it?
For most, the major source of vitamin D is skin exposure to UVB in sunlight, which waxes and wanes seasonally. In general, full-body exposure to the midday summer sun will produce about 10,000 IU of vitamin D in about half the amount of time it takes the skin to turn pink. That could be as little as 15 minutes with someone with pale skin or an hour or more in someone with darker skin.
There are many factors that affect the production of vitamin D from the sun, aside from just skin tone. If you are at an equatorial latitude, the time will be much shorter than it would be if you were at a far northern or southern latitude. The amount of skin exposed, the time of day and the time of year—both of which affect the solar angle —will affect the amount of exposure required. In summer at noon it is going to be a much shorter period of exposure required for vitamin D than winter at 4 p.m. You can estimate how much D your sun exposure is giving you with the D Minder app.
Use of 30-SPF sunscreens reduces the production of vitamin D in the skin by more than 95% (8). Sunscreens also block all of the other beneficial photoproducts produced in the skin in response to UVB. There has been a lot of concern expressed about skin cancer and sun exposure, appropriately in some cases, but maybe the pendulum has swung too far back in the other direction. Now people are unnecessarily not exposing themselves to any sun at all without sunscreen. Aiming for getting exposure about half the amount of time it takes your skin to turn pink is a good guideline, about three to five times a week if that is possible.
The best food sources of vitamin D are fatty fish, egg yolk (pastured eggs have 4-6x more), grass-fed butter, offal, certain mushrooms and fortified foods such as breakfast cereals. But dietary sources are limited and on their own, without a sun component, you are unlikely to achieve sufficient levels (9).
How do I know what my level is?
The only way to determine what you need is to regularly test the Vitamin D blood levels. This is easy to do at home with a simple finger prick test that costs £33. The results are typically turned around in a few days. Here is the link to the test kit.
Ideally this should be done 3 times a year – at the beginning of October, the beginning of Jan and the end of April. But I only do it twice, and I guess for those of you who are new to this, twice is already a big ask. In that case I would do it in October and January and consider dropping to nothing or a minimal dose in April/May.
What level should I be at?
The optimal blood level for vitamin D is still controversial. An exhaustive review of nearly 1000 studies by the Institute of Medicine in 2011, suggested that a range of 20 – 50 ng/mL (50 - 125 nmol/L) was ideal (10). Esteemed researcher Chris Masterjohn, PhD, maintains that most people should aim for their vitamin D status to be 30 - 40 ng/ml (75 – 100 nmol/L). However, vitamin D advocates such as Dr Michael Holick, MD, PhD, have suggested a much higher range. Certain labs have adopted this suggestion and use a reference range of 30 - 100 ng/mL (75 - 250 nmol/L). However, there is almost no evidence that pushing vitamin D above 60 ng/ml (150 nmol/L) has any benefit, and some studies suggest harm.
By means of comparison, in April 2020 the NHS issued a statement that an adequate blood level of vitamin D is > 30 ng/ml (75 nmol/L), but it did also mention that there may be additional benefits if you have levels between 36-40 ng/mL (90-100 nmol/L). (11)
I aim to keep my vitamin D levels around 40 - 50 ng/mL (100 - 125 nmol/L). Most functional/naturopathic doctors advocate an optimum level for vitamin D of 40 - 60 ng/mL (100–150 nmol/L), but, as you can see, this is not a perfect science and views on this subject are wide-ranging. (NB the test kit results will compare your level to the official NHS range – they can’t do anything else).
How do I achieve that level?
Maximise your sun exposure within the limits set out above. Test your vitamin D levels every four months (or as often as you can cope with). Then supplement. But don’t supplement blindly.
Normalizing vitamin D levels can happen quickly. Large intravenous doses of up to 200,000 iu can bring someone from a deficient to adequate state within days, while daily doses of 3,000 to 10,000 IU can accomplish that goal within a few weeks. It takes c1000iu per day to increase vitamin D blood levels by 10 ng/ml (25 nmol/L) so it’s easy to work out what you need. The Endocrine Society recommends doses of 1000-2000iu to achieve appropriate levels, with maximum levels of 10,000iu per day.
I check my vitamin D level regularly and now take a maintenance dose of 1000 IU per day, depending on the results. In the summer, I often cease supplementation completely.
Vitamin D supplements are inexpensive and come in capsule, soft gel, drop and spray formats. All are fine – it’s down to preference. Unless on blood thinners such as Warfarin, it is best to get a combined vitamin D3 and K2 supplement, as K2 – a very important and undervalued vitamin in its own right - reduces the likelihood of vitamin D toxicity.(12).
I buy a lot of my supplements from The Natural Dispensary. You will need to set up an account, but anyone can do this. There are literally hundreds of vitamin D products on this site. Here are some links to products that you could consider. They are good brands, and use the preferred form of vitamin D, cholecalciferol:
Vitamin D3 Complete - softgels (Allergy Research Group) This product supplies Vitamin D3, Vitamin A and K2 in a balanced combination. Each capsule delivers 2,000iu of Vitamin D3.
Vitamin D3 + K2 - capsules (Cytoplan) This product contains 4,000iu Vitamin D3 and 100ug Vitamin K2 and is suitable for those who need to raise their levels of D3/K2
Vitamin D3 drops (Nutri). This is an emulsified liquid vitamin D formula that allows convenient, flexible dosing. Each single drop provides 1000iu of the preferred form of vitamin D, cholecalciferol.
If you can, take it with or just before the meal that contains the most fat, as vitamin D (and K) is a fat-soluble vitamin and so this increases the body’s absorption.
Can I over-supplement?
Yes, you can. With vitamin D, balance is key. Research suggests that too much may be a problem. Because of the justifiable focus on deficiency, a lot of practitioners are not sufficiently aware of this. As I said above, there is little evidence that raising levels above 50mg/mL is beneficial, and there is some evidence it may be harmful in certain cases. Higher levels, certainly in the toxic range above 100 ng/mL, but even in the upper part of the normal range (80-90 ng/mL, 200 – 225 nmol/L), have been linked with decreased bone density, calcified blood vessels and kidney stones.
Recent work by researcher Chris Masterjohn says that vitamin D toxicity is in part caused by a corresponding deficiency in vitamins A and K2. The fat-soluble vitamins A, D and K work synergistically, and adequate vitamins A and K2 protect against the toxic effects of excess vitamin D (13). Cod Liver Oil is an excellent source of vitamins A and D, and pastured butter (Kerry Gold) and ghee (clarified butter) great sources of vitamin K.
Takeaways
You should not allow yourself to be deficient in Vitamin D. There is too much at stake
Although the precise blood level that is considered optimal is still debated, it isn’t difficult to find a level that is in the sweet spot of most practitioners/researchers.
You might be able to fill most of your vitamin D needs from sunlight if you don’t have a typical office job and spend much of your time outside.
Food helps, but doesn’t sort entirely, and there aren’t that many sources.
Supplementation is safe provided you know what your current level is and where you are headed. Vitamin A and K2 alongside will help in preventing any toxicity.
Testing a few times a year is advisable and not expensive, invasive or time-consuming. (6)Vitamin D3 Complete - softgels