Your blood levels of THIS control your immune system, hormone balance, and energy levels

Well, it's almost winter here in the northern hemisphere, and that brings along with it a health risk that most people don't even think about often... your blood levels of vitamin D3.

Your vitamin D levels are one of THE biggest factors for how often you'll get sick this coming winter, and I've seen estimates that as much as 80-90% of the North American population has sub-par levels of vitamin D, with as much as 50% potentially clinically deficient.

As you may know, this is the main reason people get sick more often in the winter vs the summer... there's just such a major connection between your vitamin D levels and the strength of your immune system, as well as your hormone balance.  And your vitamin D levels are highly regulated by how much mid-day sun exposure you get throughout the year.

Not only that, but your vitamin D levels also control much of your hormone balance too, as well as energy levels, and low vitamin D levels in winter from lack of sun exposure is a major problem for many people (yes, even in sunny locations like southern California, as you'll see why in a minute).

Here's something you NEED to know about the fall and winter in the northern hemisphere...

At this point in the season, in MOST of the United States (except the very far southern parts of the country), and probably 100% of Canada at this point in the year (mid Oct), as well as all of the northern portions of Europe, the sun's UVB rays are already too weak in the fall to trigger vitamin D production in your body... even at peak sun levels mid-day, depending on both latitude and altitude of each location.

According to vitamin D researcher Dr. Joseph Mercola, while UVA rays from the sun make it to the surface of the earth regardless of the angle in the sky, the sun needs to be at least approximately 30-40 degrees above the horizon for UVB rays to penetrate the ozone layer of the earth and make it to the surface.  And it's only UVB rays (not UVA rays) that trigger vitamin D production in your skin. 

This varies in each location based on latitude, altitude, smog and other air pollution that can block UVB rays, and other factors.  For example, 30 degrees sun height in the sky might be sufficient at a higher elevation above 5000 feet on a clear day with no air pollution, but might not be sufficient at sea level in a smoggy city.  At sea level in a smoggy city, you might need at least a sun angle of 40 degrees or more for UVB rays to be sufficiently strong enough to produce vitamin D in your skin.

Therefore, based on the latitude that you live, the time of day, as well as time of year, there are only certain times that the sun is actually greater than 30-40 degrees above the horizon.  So keep in mind that you are only capable of producing vitamin D from the sun at any times of day or times of year that the sun is at least 30-40 degrees or higher above the horizon as an approximation.

Temperature is not a factor in how much vitamin D producing UVB rays that you get (except for the fact that you're more willing to expose more of your skin when it's warmer), but as I mentioned, the clarity of the air is a major factor as cloudiness, smog, and other air pollution can block the UVB rays and prevent you from producing vitamin D even if you're outside on certain days.

*By the way, the easy way to estimate what 40 degrees above the horizon looks like is to think that 90 degrees would be the sun straight directly above your head, and 45 degrees would be halfway down to the horizon.  So 40 degrees would be if the sun is just slightly below half way from the horizon vs directly over your head.

I recently found a table on a Navy website that gives you exact calculations of the sun's height in the sky on any day of the year and at any location -- latitude being the key here.

As an example, in New York City (or any cities at a similar latitude), in the strongest sun month of June, you have a sun angle of 40 degrees or more above the horizon all the way from 9am through 5pm (according to the Navy table above) ... However, once you get to mid-October, the sun no longer goes above 40 degrees at all. 

So even on a sunny day in late October or November in a latitude such as New York City, you might not produce any vitamin D, even if you were out in the mid-day sun, since UVB rays are not strong enough at those low sun angles in the sky.

That means your time of year that you could actually produce vitamin D in your skin would be approximately March through early October at most latitudes in the northern two-thirds of the US. 

Further north into Canada (depending on how far north we're talking), that time span for vitamin D production from the sun would be a few weeks shorter on both sides of the year compared to that example of New York. 

And if you go further south, into Florida, southern Texas, Arizona, southern California, and other lower latitude states, that time span that you can produce vitamin D would be several weeks longer on each side of the year than our example of New York, but there would still be a couple months in the deepest part of winter that you can not produce vitamin D in your skin, even on sunny days because the sun is simply too low in the sky and UVB rays too weak.  The only exception would be the absolute lowest latitudes of Hawaii, southern Florida, southern Texas as examples in the US... basically, any location south of approx 30 degrees North Latitude have strong enough UVB rays to produce vitamin D all 12 months of the year.

The same scenerio can be said for equivalent northern latitudes if you live in Europe.  And of course, all of this occurs at the opposite time of the year in the southern hemisphere, again all based on how far a particular location is from the equator.  I show you exact examples of your "vitamin D winter" based on sun height in your area in this blog post here.

So what does all of this really mean to your health?

Well, it means that NOW is the time to start paying attention to your vitamin D levels if you want to keep your hormone balance optimized, and keep your immune system strong enough to fight off any sicknesses this winter.

Although old guidelines say that anything over 32 ng/dl for blood levels of vitamin D3 is good, new research about vitamin D is suggesting that getting levels between 50-80 ng/dl is what is considered optimal to actually see maximum benefits on your hormones and your immune system.

Did you know that many people are surprised to find out that their blood levels of vitamin D are shockingly low with levels in the teens or 20's.  No wonder they get sick so often!

And for the guys reading this, low blood levels of vitamin D3 can also spell low Testosterone levels, so make sure to get your D levels where they need to be if you want optimal T levels! 

Not surprisingly, due to the sun-phobic mentality that's been hammered into our heads by the media, along with lack of time spent outdoors and/or excessive use of chemical sunscreens, most people have chronically low vitamin D levels even in the summer, and I mentioned earlier, this greatly affects your immune system as well as your hormone balance.  So now that winter is coming, it gets even worse as Vitamin D levels can drop another 50% in the winter if you're not supplementing.

As a general rule for North America and Europe, in order to maintain a strong immune system through the winter, most people will need to supplement with vitamin D3 from approx October through March, unless you live in Hawaii (the southernmost latitude in the US), southern Florida, or any latitude further south than about 30 degrees N latitude. 

Personally, I don't supplement with vitamin D3 in the summer months, because I do a LOT of outdoor activities like hiking, mountain biking, and other sports, so I get my D3 from the summer sun, and based on my test results, I seem to stay above 50 ng/ml in the summer without needing supplementation.  But starting in October is when I start taking 5000 IU daily of an oil-based D3 supplement.  I personally use this oil-based vitamin D3 supplement as it uses heart-healthy coconut oil instead of inflammatory refined soybean oil as the base..

I talk more about vitamin D and it's vitally important relationship to your ability to fight off sickness at this article below... and I also give you 6 other powerful tips to keep yourself from getting sick year round:

7 powerful tips to NEVER get sick again

Another article I put together on this topic that you should read is here:

Study shows higher vitamin D levels makes you equivalent to 5 years younger

Talk to you soon!

Mike Geary
Certified Nutrition Specialist
Certified Personal Trainer