The importance of Vitamin D
The sun’s reaction with our skin is how we evolved to get most of our Vitamin D. I aim for at least an hour of full sun whenever I can…
In a nutshell
Vitamin D3 is an important hormone that influences human metabolism
Sunlight interacting with healthy skin is by far the most important source of Vitamin D3
Many people (most?) do not produce or consume enough Vitamin D
Insufficient Vitamin D3 is associated with frequent infections, osteoporosis, and other so-called chronic diseases
Vitamin D3 is a fat-soluble steroid hormone [1,2] which is involved in a large number of important metabolic functions throughout our body.
I’ve previously written about the importance of the micronutrient, magnesium. I found a lot of information about magnesium and I was able to describe the effects of, and how to remedy its depletion in me. Information about Vitamin D3 is less common, more dispersed, and less straight-forward. Also, I can’t point to any personal experience that I’d connect with Vitamin D3 or a lack of it.
Nevertheless, I have become convinced that Vitamin D3 is a bedrock micronutrient that we should take care to get enough of.
Here’s what I’ll cover:
• What is vitamin D3 and why is it important?
• Are we getting enough, and what happens if we don’t?
• Getting enough Vitamin D3 and causes of deficiency
What is vitamin D3 and why is it important?
Vitamin D3 is involved in many fundamentally important functions throughout our body (Table 1). Most of our tissues use it and will malfunction if we don’t get enough [3].
Historically, Vitamin D3 was associated with bone health (e.g., weak, soft bones, osteoporosis, rickets), by regulating the micronutrients calcium and phosphorus. We now know that vitamin D is much more broadly important because, for example, it influences our immune system [3,4] and is required by our body to clear damaged cells and generate new ones (autophagy) [1] (Table 1).
Table 1: The role of Vitamin D3 throughout the human body
Are we getting enough and what happens if we don’t?
Are we getting enough vitamin D3?
What is enough? This is one of those questions that I believe we should consider for ourselves in light of important variables such as sun exposure, geographic location, skin colour, and age. I’ve found the literature quite confusing so instead of measuring my blood concentration, I’ve simply tried to safely maximise my sun exposure, eat real food and take a daily supplement.
If you are interested in a more scientific approach, I’d start by reading reference 3. It describes diagnostics, recommended levels, and associated health effects.
Details aside, it is estimated that there exists widespread deficiency in Vitamin D3 affecting around one billion people worldwide [3], especially in higher latitude, lower sun areas such as Scotland [6].
Consider a small sample of examples:
40% to 100% of US and European elderly people not in nursing homes are low in Vitamin D3 [3]
More that 50% of post-menopausal women medicating for osteoporosis were low [3]
Of 2,235 healthy adults in Scotland, 65% were deemed deficient, 35% severely so [6]
Implications of insufficient vitamin D3
I’m struck by two things. Firstly, Vitamin D3 is involved in very important basic aspects of human health (Table 1). Secondly, if those basic aspects of our metabolism aren’t functioning properly, serious ill health can ensue (Table2).
Lack of Vitamin D3 has been known for some time to cause skeletal diseases such as weak and soft bones, osteoporosis, and rickets for example [1,3]. These days, there is mounting evidence that Vitamin D3 deficiency may also lead to a range of non-skeletal, so-called chronic diseases (Table 2).
Table 2: Vitamin D deficiency is associated with a range metabolic, autoimmune and infective diseases
However, the health effects of insufficient Vitamin D3 on non-skeletal diseases are still debatable. After a 2014 review of the literature, a team of researchers concluded that “…highly convincing evidence of a clear role of Vitamin D with highly significant results…does not exist for any outcome”. Nevertheless, the same authors also stated that “… evidence exists for a correlation between high vitamin D concentrations and low risk of…” a range of so-called chronic diseases [7].
For me this means whilst the situation isn’t hard and fast, a risk exists and it’s worth each of us exploring further.
Getting enough Vitamin D3 and causes of deficiency
Getting enough vitamin D3
Vitamin D3 can be obtained in three ways but its primary natural source is an interaction between cholesterol and sunlight in our skin. Secondary sources from diet and supplements can be important, especially in regions with low sunlight exposure.
Sun
Our body manufactures Vitamin D3 through a series of steps that uses cholesterol in the skin as a starting material [5, p.217] to react with the sun’s rays. The result of this initial reaction is transported in our blood to the liver which creates yet another intermediate compound which is then transported to our kidneys for the final conversion to the active form, Vitamin D3 [1,3,4].
As our ancestors migrated north from Africa towards higher latitudes their skin lost melanin pigmentation and lightened. This is believed to be an example of an evolutionary adaptation in that it improved an individual’s ability to survive and reproduce [9] by filtering less of the sun’s rays and optimising Vitamin D production in the lower sun-intensity part of the world [10].
It can be seen from Table 3 that even minimal exposure to the sun’s rays does provide much more vitamin D than any dietary source.
I try for an hour of sun each day whenever I can, preferably during exercise
My own experience with sun exposure has been interesting. As a child growing up in Scotland and during my later life in America, I had to be very careful to avoid the sun apparently burning my skin. Even early and late in the day I used sun screen and wore protective clothing. Then…in the summer of 2022, I noticed that despite prolonged mid-day exposure and wearing only shorts and flip flops, I was not getting sunburned. The same happened this year (2023). My initial experience coincided with the fifth year after I’d started to avoid seed oils. I’ve described this at length before, so suffice it to say that I blame seed oils for my sunburn, not too much sun. Now, I aim for at least an hour of full sun on my legs, arms and torso as often as possible whilst boating, running and gardening.
Incidentally, the fact that cholesterol is the starting material for our body’s manufacture of Vitamin D3 is interesting. It appears also that we make Vitamin D3 in proportion to the amount of cholesterol in our skin [5, p.217]. In other words, the more cholesterol, the better for making Vitamin D3.
Food
Dietary sources of Vitamin D provide much less than we can produce naturally with minimal exposure of healthy skin to sunlight (Table 3) [3]. That said, fish and mushrooms are a decent source when wild-caught and sun-dried, respectively.
Table 3: Natural sources of Vitamin D. IU = International Unit. 1,000 IU – 25 micrograms
Supplements
I decided a long time ago that lack of Vitamin D3 was a risk factor for my health and I decided to take a supplement.
I take a daily 5,000 IU supplement that also includes magnesium and Vitamin K2. Magnesium is necessary for activating Vitamin D3. Vitamins D3 and K2 work together to enable proper calcium absorption and distribution.
Causes of Vitamin D deficiency
Given its primary evolutionary source of Vitamin D, anything that reduces our exposure to natural sunlight should be expected to potentially cause deficiency. Table 4 shows that reduced skin synthesis can be caused by sunscreen use, skin pigmentation, latitude and season, and grafted skin.
I was surprised to read just how effective low-factor sunscreens actually are. We don’t need high factor creams to reduce Vitamin D production to practically zero.
“It is estimated, for example, that those of us living north of the 35th parallel may not be able to produce much if any Vitamin D3 from November to February [3]. That covers most of Europe, Asia, and N America in the northern hemisphere…!”
Each of us alive today is evolved from dark-skinned ancestors living near the equator. Our ancestors’ skin contained high amounts of melanin which acts as a natural sunscreen to protect from the damaging amounts of the sun’s radiation in that part of the world, whilst still allowing sufficient Vitamin D production in their skin. Unfortunately, dark-skinned people today who choose to live further from the equator may suffer from Vitamin D deficiency because their natural melanin sunscreen is too efficient for the lower amounts of sunlight in their new home.
Even light-skinned people like me can suffer from Vitamin D deficiency at higher latitudes. It is estimated, for example, that those of us living north of the 35th parallel may not be able to produce much if any Vitamin D3 from November to February [3]. That covers most of Europe, Asia, and N America in the northern hemisphere…!
Table 4: Causes and associated effects of Vitamin D3 deficiency [3]
Summary
Three things have become apparent to me. A healthy human existence requires adequate levels of the hormone Vitamin D3. Our species has evolved and adapted to create its own Vitamin D3 through a series of biological steps that begin with the sun’s rays interacting with healthy skin. Many, perhaps most, of us suffer from a deficiency of Vitamin D3 and may, consequently, be quietly ill.
Sickness caused by Vitamin D3 deficiency may be yet another example of modern mismatch in which the bodies we have inherited from our ancestors are not suited to the environment in which we live. Consider osteoporosis, for example, for which Daniel Lieberman [9] provides the following:
“The worst possible scenario is to be a sedentary post-menopausal woman who didn’t exercise much when she was younger, doesn’t eat enough calcium, and gets insufficient Vitamin D.”
Piling it on…
“All in all, millions of years of natural selection did not gear our skeletons to mature in the absence of plentiful physical activity along with lots of calcium, Vitamin D, and protein.”
I suspect that many of my friends are wary of sun exposure because of modern guidelines designed to avoid skin cancer. I hope they’ll read this and think about those guidelines considering the cancer risk associated with insufficient Vitamin D3.
I’m lucky, I think I’ve figured out how to get enough Vitamin D3 with adequate healthy exposure to the sun plus appropriate supplementation.
References
Clement, J.W. and Loberg, K. (2019) The Switch: Activate your metabolism for a healthier life. London, Simon and Schuster
Spector, T. (2022) Food for Life: The new science of eating well. London, Jonathan Cape
Holick MF. Vitamin D deficiency. N Engl J Med. 2007 Jul 19;357(3):266-81. doi: 10.1056/NEJMra070553. PMID: 17634462.
Nagaria T D, Shinde R K, Shukla S, et al. (October 10, 2023) The Sunlight-Vitamin D Connection: Implications for Patient Outcomes in the Surgical Intensive Care Unit. Cureus 15(10): e46819. doi:10.7759/cureus.46819
T.D. Noakes et al (Eds.), Ketogenic: The science of therapeutic carbohydrate restriction in human health (1st ed, pp 3-700). Elsevier
Zgaga L, Theodoratou E, Farrington SM, Agakov F, Tenesa A, Walker M, Knox S, Wallace AM, Cetnarskyj R, McNeill G, Kyle J, Porteous ME, Dunlop MG, Campbell H. Diet, environmental factors, and lifestyle underlie the high prevalence of vitamin D deficiency in healthy adults in Scotland, and supplementation reduces the proportion that are severely deficient. J Nutr. 2011 Aug;141(8):1535-42. doi: 10.3945/jn.111.140012. Epub 2011 Jun 22. PMID: 21697298; PMCID: PMC3361015.
Theodoratou E, Tzoulaki I, Zgaga L, Ioannidis J P A. Vitamin D and multiple health outcomes: umbrella review of systematic reviews and meta-analyses of observational studies and randomised trials BMJ 2014; 348 :g2035 doi:10.1136/bmj.g2035
Dinicolantonio, D. and Land, S. (2020) The Immunity Fix; Strengthen your immune system, fight off infections, reverse chronic disease, and live a healthier life. Self published
Daniel Lieberman (2014) The Story of the Human Body. London, Penguin Books
Gluckman, P. and Hanson, M. (2008) Mismatch: The lifestyle diseases timebomb. Oxford, Oxford University Press