Survival...... Ch. 3 "The Cholesterol also rises"

This chapter takes a look at a couple different factors.  Vitamin D, Folic acid and cholesterol.

In a nutshell:
Vit D is created by our bodies in response to sunlight at the SAME time though, natural sunlight destroy's our body's natural reserve of folic acid.  BOTh of these are quite important for overall functioning.  You may have heard of a disorder known as Rickets in children. This is due to vit D deficiency.  In adults Vit D is important for MANY biological processes and Vit D Deficiencies in adults have been "shown to play a role in development of dozens of disease - everything from many different cancers to diabetes, heart disease, arthritis, psoriasis, and mental illness."

HOW do we make vitamin D?  We convert cholesterol!! (Remember we talked about how cholesterol is found in our cell membranes?!?!) What stimulates this conversion?  Certain wavelengths of sunlight known as Ultraviolet B (UVB)

So.... Being in the sun is good for getting your Vit D levels up but BAD for keeping your folic acid levels up.  How have humans who are in very sunny environments adapted to this?!?!!?  DARK SKIN!!!  Not ONLY is it an adaptation against sunburn....you don't absorb as much UVB therefore you keep your folic acid levels high!!

Interestingly enough - what determines how many of our melanocytes (the cells that produce melanin - the pigment in our skin) is all based on visual signals.  As soon as our optic nerve senses sunlight it sends a message to our pituitary gland that says - "hey - i'm in the sun - make some pigments so i tan and not burn!!!" WELL...... if you are wearing SUNGLASSES - it actually takes LONGER for your body to know that you are in the sun since you are messing with your optic nerves "view"

Alright - this shows us how dark skinned people have adapted to maintain their folic acid levels..... HOW do they maintain high Vit D levels then?    Well, i mentioned about that Vit D is converted from cholesterol... you, people from areas such as Africa where darker skin is prominent ALSO tend to have very high cholesterol levels.  This way, whatever UVB that IS able to penetrate their skin is maximized with the availability of lots of cholesterol.

What about light skinned people who don't see daylight as often such as in norther Europe?!?  They also have adapted to this by carrying a gene that causes their cholesterol to be relatively high all the time to maximize the small bit of UVB they are exposed to in a year.

ANOTHER interesting trait that we see more often in African Americans is the tendancy to have high blood pressure.  You do NOT see this as much in Africans living in Africa - but those who are descendants of  slaves..... Lets look at why this may be.  High blood pressure goes hand in hand with Salt consumption.  If you have  natural tendency to retain high levels of salt in your blood, it messes with osmosis (remember that) and causing them to retain water as well to try and balance the extra salt in their cells. Well.... when Africans were being taken over on slave ships against their will, conditions were pretty bad, they were probably not fed much or received much fresh water.  MANY died.  Those that did NOT only survived because they had SOME sort of advantage........  Well, being able to naturally retain salt AND water would help them from dehydrating.   So it allowed them to survive the trip to America, but now puts them at a high risk for Hypertension (high blood pressure)  Why would nature "select" for something that could ultimately kill you some day?!?!?!  Because its the only thing that is keeping you alive for TODAY!