Vitamin D is Way More Important Than Previously Thought

You may not have given Vitamin D much thought before but you really should.

Scientists are.

And the conclusions are clear: Vitamin D deficiency is linked to more diseases and health concerns than anyone could have guessed.

Vitamin D is Way More Important Than Previously Thought

More scientific research has been done on Vitamin D deficiency in the past year than was done all throughout the 1990s.

Using “Web of Science”, it’s clear to see the steep increase in scientific articles relating to Vitamin D deficiency.

The number of articles in Web of Science about “Vitamin D Deficiency” has increased dramatically in recent years

The reason for this new interest around Vitamin D is that scientists are realizing Vitamin D is more important than previously thought.

Vitamin D deficiency is linked to a very large number of diseases , probably the scariest of which are cancer and heart disease.

It can cause depression and weak bones, which can be serious in children (rickets) and elderly (osteomalacia).

The unfortunate fact is that, more than 40% of American adults are deficient in vitamin D but taking too much as a supplement can have serious health impacts as well (see below for more on this).

To further complicate matters, measuring vitamin D levels in our bodies is inaccurate and not common practice.

So how do you know how much you should get?

What is Vitamin D?

Vitamin D is actually a hormone rather than a vitamin (technically it is a prohormone but I don’t want to go too into that, you can read more about it here).

That’s why it is involved in so many processes in the body and linked to so many ailments when we are deficient.

Unlike other vitamins that your body gets from food, your body actually produces most of its Vitamin D (it is “endogenous” for those that like fancy words) in the kidneys and the body needs sunlight for this process.

This why people tend to be Vitamin D deficient during the winter months. It’s not just bad the weather, but also shorter days and wearing more more clothes limit our exposure to the sunlight needed to produce vitamin D.

Can I Just Sit by a Window?

Getting sunlight without going outside gives you all the bad with none of the good.

First thing to understand is that UV is not just UV – there is UVA, UVB, and UVC.

UVC is filtered out in the upper atmosphere so we don’t need to worry about it too much.

UVB is what is needed to make vitamin D…but unfortunately it’s filtered out by glass.

UVA can cause skin cancer but is not filtered by glass.

Getting sunlight by sitting next a window exposes you to UVA which can cause skin cancer but not the UVB needed to make Vitamin D

Getting sunlight by sitting next a window exposes you to UVA which can cause skin cancer but not the UVB needed to make Vitamin D

That’s why Americans that drive a lot are way more likely to get skin cancer on their left side rather than their right.

Tip – tinted windows filter out 4 times more UVA than untinted windows.

So sitting by a window inside does not have the same benefit as getting outside and getting some sun.

Also, then you’re just inside…which is lame. Come on, go outside.

Should I take vitamin D supplements or get more sun?

Deciding to take any supplement is a very personal decision so all I can do is provide some information so you can make your own decision.

You may be wondering if eating foods rich in Vitamin D can make up for a Vitamin D deficiency and the answer is: probably not.

That’s because only about 10% of the Vitamin D we need comes from our diet.

So even if you really amped up your Vitamin D intake through foods like fortified milk and fish, lets say you double the intake of a normal person, you still only have 20% of what you need.

Personally, I feel like I benefit from taking 400 international units of vitamin D per day, especially during winter. This is a pretty low dose so I’m being quite conservative but chances are I’m not Vitamin D deficient.

I honestly feel a little perkier when we’re having a particularly grey February and I’m taking this supplement. Then I tend to cut back to every other day or cut it out completely during the summer.

The common recommendation for most people is 600 – 800 IU per day and the mayo clinic says 1000-2000 IU is generally safe, but there is some controversy surrounding Vitamin D supplementation.

It has been found that really overdoing it by taking 10,000 IU or more can cause calcium in the urine which causes kidney stones or calcium deposits in the veins which can lead to heart attacks.

I know that sounds scary but that’s more than 10 times the recommended daily dose.

The largest study on Vitamin D, called VITAL, included 25,000 people split into high vitamin D doses, taking 4,000 IU per day, and no vitamin D supplement, found that the vitamin D at that level did not lead to high levels of calcium in the blood.

The VITAL study also found that Vitamin D did not help prevent the occurrence of cancer but did significantly lower cancer deaths.


Vitamin D deficiency is very common and associated with a lot of negative health effects. Scientists have given it a lot more attention in the past decade than they ever have before because evidence suggests Vitamin D is more important than previously thought.

Getting sufficient Vitamin D poses a problem because you can’t get enough vitamin D from your food and getting more sun means increasing your risk of skin cancer. That’s where supplementation comes in. The recommended dose for Vitamin D supplementation is 600-800 IU per day and you shouldn’t overdo it because that can have negative consequences as well.

Did you know that simply spending time outside has numerous health benefits besides getting Vitamin D? Check out 7 Health Risks Reduced by Spending Time Outside and be sure to check out the cool infographic at the bottom.

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