This post is exactly what the title and graphic suggest: it is a post talking about one of the essential vitamins for good health, Vitamin D.
Vitamin D is a sunshine vitamin, and it is made in the skin when exposed to UVB radiation. Unfortunately, our paranoia over skin cancers has led people to believe that any sun exposure is bad. Turns out, as it mostly does with health issues, that there is a happy medium.
Too much sun is bad, but some sun is necessary. This post deals with:
- The problem
- The solution
- Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease
These are two studies by Dr Michael Holick available free online and should be read by anyone who wants to know more. I will be quoting from these studies, so you should get the gist of them by reading this post.
I hope that after reading this post, your interest will be piqued enough to motivate you to download these studies and watch this very long talk by Dr Holick. If not, applying the recommendations from this post will already do you good.
You may also benefit from getting his book, ‘The UV advantage’.
As well, it would be great to watch this presentation: The Vitamin D Pandemic and its Health Consequences
Now, let’s begin.
The root of the problem
This goes back to our ancestors who lived in the tropics. Back in the day, (2,000,000 years ago) our ancestors got all the sun they needed to make enough Vitamin D. Interestingly, it is the Ultraviolet B (UVB) radiation that causes the skin to make Vitamin D in the first place.
Now the problem presents itself. Many parts of the world are now gripped by the icy hand of winter, and thus, people are wrapped up in clothing and don’t go outside as often. Very likely, sun exposure goes down and Vitamin D levels plummet. Furthermore, our lifestyle nowadays revolves largely around indoor work (some professions are exceptions). Furthermore, when many finally do get under the sun, they apply sunscreen, which blocks out 95% of UVB radiation. 
Now, Vitamin D also comes from our diet, but only in small amounts. For example, a 250ml glass of milk contains 100IU of Vitamin D. As we will see later, this isn’t enough. As Dr Holick concludes, “more than 90% of the vitamin D requirement for most people comes from casual exposure to sunlight.”
Traditionally, the problem associated with Vitamin D is rickets. In this case, the group affected is children. Administering about 400IU of Vitamin D with cod liver oil a day back in the 1800s was what largely curbed the problem. Unfortunately, what worked for children is not going to work for adults.  So if a small child needs 400IU (4 glasses of milk) of Vitamin D, what would an adult need? I will come back to this later, but now, more bad news.
Not enough Vitamin D causes other problems, both in children and adults. Children may fall prey to rickets of course, and to top that off we have stunted growth, muscle weakness, and many other bad things. Adults not getting enough Vitamin D may have poor calcium absorption, which leads to diseases like osteomalacia. The elderly are particularly affected, and you can imagine that brittle bones and muscle weakness can potentially lead to falls and hip fractures. Furthermore, when you get older, your skin starts to go wonky, and you actually produce less Vitamin D with the same amount of sun exposure.
Enough of that, you can Google the results of a Vitamin D deficiency. But we just need to know that: Not enough Vitamin D = Bad things happen.
There are a couple of things to do, so I will break down the solution into a couple of segments.
There have been a few different requirements thrown out, but they all fall within some pre-set range. Note that there are two common units of measurement for Vitamin D blood concentration. There is the nano-moles per Litre (nmol/L) and the nanograms per millilitre (ng/mL). Make sure you know the units, because the values differ for each unit. Confusing, yes, but that’s the fickle scientists for you.
Anyway, Dr Holick suggests that you keep Vitamin D concentration between 75-125nmol/L (equivalent to about 30-50ng/mL), with others suggesting upwards from 40-60ng/L to even 75ng/L.
Regardless, I must make this note, that problems associated with Vitamin D are due to not having enough of it. Thus, we are better off asking, “How much is too much?”
The answer to that is that studies show that blood concentrations of 250nmol/L (or 100ng/L) is completely safe. Some studies even show levels of 150ng/L not giving signs of Vitamin D intoxication.
Given that most of the American population is Vitamin D deficient , having levels lower than 50nmol/L, there is cause for concern.
This is the shortest but most important section. The only way at present to test for a person’s Vitamin D status is through a blood test which measures the serum concentration of 25(OH)D (pronounced ’25 Hydroxy D’) and not anything else. There are various forms of Vitamin D, but we are only interested in this form.
The last point here is that it would be wise to test your Vitamin D status at its highest and its lowest. Namely, after Winter for the lowest, and after summer for the highest. If you live in the tropics, any time of the year would likely do.
Now that you know your Vitamin D level, its time to boost that to the 75-125nmol/L range.
There are two ways which you can do this. The first would be to get out into the sun, and the second would be to take supplements.
The first is simple, take your clothes off and run around in the sun! On a more serious note, Dr Holick has recommended that fair-skinned folk can make do with about 10-15 minutes of sun exposure at the brightest time of the day (11am – 1pm). After this, sunscreen should be applied to stop the negative effects of over-exposure.
However, darker-skinned individuals need more exposure. Quoting Dr Holick, “It has been documented to require 5-10 times more exposure to produce a 30-fold increase in blood concentration of Vitamin D in an African-American subject compared to a Caucasian subject.”
Hence, the recommendations should change as a result. In this regard, I have not seen precise recommendations. So, it depends.
A final note on the first method is that the amount of sun reaching Sweden in November is going to be much different from the sun reaching Australia at the same time of the year, so this is a very variable recommendation.
Hence, we have our second solution. This is simply to take supplements, usually in a capsule form to boost the Vitamin D levels in the blood. This is arguably easier and more precisely measurable.
You should know your Vitamin D status after you have tested it. Say it is hovering at 20ng/mL and you would like to boost it to 50ng/mL. This is where the general rule applies, that for every 10ng/mL increase you want, you should take 1000IU Vitamin D daily. This varies of course, but it is generally accurate.
So our subject would take 3,000IU every day for 6 months. After that he gets his Vitamin D levels checked, and hurray, its now at 48ng/mL. He’s a big guy, so he needs more Vitamin D, but his levels are now within the recommended range and he’s very happy.
As with anything related to health and especially supplementation, there is bound to be the issue of safety. The first one is the potential for overdose.
If you take pills or powders, make sure you know how much is in each pill and how much you are taking daily. Though rare, vitamin D overdose can happen. You could easily measure your Vitamin D levels to monitor this if you wanted to.
The good news is that this is very unlikely.
As seen in this graph by Michael Holick and colleagues, a 1 time administration of 50,000 IU of Vitamin D in capsule form to normal patients only spiked blood Vitamin D to around 80-90ng/mL; below the level of intoxication.
Note that this is for Vitamin D alone, so also watch to see if your supplements could contain other nutrients which could potentially lead to an overdose of that nutrient. (Eg: Some Vitamin D supplements come with Calcium, and could be overdosed)
A Brief but Important Conclusion
Vitamin D is important for healthy function, and many people do not get enough of it.
The best advice would be to take massive action. Get a blood test to determine your individual 25(OH)D serum concentration. Then get out into the sun more often and take Vitamin D supplements.
With some awareness and of course some cash investment, the problem will be easily solved. For long-term health, I think it is well worth it.
 This is apparently for an SPF 15 sunscreen. Higher SPF sunscreens would block slightly more, approx 98%
 It should be noted that a larger body needs more nutrients, and Vitamin D is no exception.
 1 ng/mL Vit D is equivalent to about 2.5 nmol/L.
 Dr Holick reports the findings of other researchers in his papers. Of which, some include the findings that 54% of nursing home members and 38% of nursing home residents were Vitamin D deficient. Also, another study showed that 47% of white girls aged 9-13 were Vitamin D deficient at the end of winter. Yet another shows that more than 50% of African American teenagers in Boston were Vitamin D deficient, and the list goes on.
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