We should all know how important it is, but … an alarming number of people that I have spoken with do not realize how important it is for our health and well being.
It is likely that many of the diseases that we consider to be diseases of the developed world are due at least in part to decreasing vitamin D. These diseases include heart disease, autoimmune diseases, and diabetes. And it turns out that the levels of vitamin D that you need to prevent those illnesses is much higher than the level you need to prevent rickets, which is why in the vitamin D community we think that there is a widespread vitamin D deficiency, even though we really don't see rickets very often.
In the US, there are several diseases such as high blood pressure and type 2 diabetes that are much more prevalent in black people than in other ethnic groups. This could very well be due to lower levels of vitamin D, because darker skinned people need to spend much more time in the sun to generate adequate vitamin D.
They're doing some research at the university of Minnesota on autism linkages to vitamin D linked to the Somali population in Minneapolis.
Apparently there isn't even a word for this condition in the Somali language but it has been appearing in the Somali community there at an alarming rate. While it does sound plausible that a rise in autism coincides with a decrease in vitamin D, what with the advent of indoor entertainment, but of course we all know correlation != causation.
I think the Somali population could prove to be a very interesting control group.
I'd be interested in more study with maternal vitamin D status as a risk factor for autism in children as well. There is some thought that autism might be due to maternal antibodies attacking the fetus, causing problems during brain development.
As you can see vitamin D does a whole lot more than prevent rickets, though. Vitamin D regulates a whole bunch of stuff including blood pressure (it inhibits the Renin enzyme which regulates the body's mean arterial blood pressure), the immune system, hormonal activity (including insulin), and many other important biological processes.
A lot of people just think spending time in the sun is enough, but like most things it is more complicated than that.
In other words more exposure to solar radiation.
It turns out solar radiation correlates with skin tone at a strength of about 60-70%. There is another explaining factor that is also very important.
Vitamin D in your food.
One control group that was studied for vitamin D levels … Inuits. They live very far north, yet they have darker skin than many Europeans.
It's because the Inuit diet is very high in fish which have substantial amounts of Vitamin D, while most white Europeans and Americans are often Vitamin D deficient due to our diets. Hence we have lighter skin despite having more solar radiation.