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!

Survival of the sickest ch:2 A spoonful of sugar helps the temperature go down

This chapter takes a look at an all to common disorder - Diabetes.  The idea for why this gene may have been advantageous at some point came from two interesting places.  Grapes and a Wood Frog.  First with grapes.  They explored the fact that in preparation for the first frost grapes do two things.  #1 they release a lot of their water #2 they increase the amount of sugar.  This is why ice wine is so sweet but so expensive.  Not as much can be produced since they released a lot of their water.  This made researches look at another disorder.... with similar "symptoms"... one in which you loose a lot of water (through urine) and have an increase in blood sugar........... You bet - Diabetes!!  What it came down to was that having extra sugar in their blood, diabetics were more likely to survive the last ice age.  Having sugar added to water decreased the freezing temperature.  So this likely allowed some people's blood to handle the severe cold that occurred in this time.  That is why it is THOUGHT (there is still a lot of debate on this apparently) that there is a high prevalence of people of norther European descent that carry this gene.

Survival of the sickest Chapter 1 - Ironing it all out

This chapter deals with a disorder known as hemochromatosis.  Hemochromatosis is a genetic disorder that causes the body to think that it constantly needs iron therefore people with it are in essence "rusting" to death.  The gene that causes this is very common among those of Western European descent..... Let's look at why. This brings us back all the way to the bubonic plague.....  NORMALLY, more iron in the blood = bacterial buffet!!  Almost all living organisms THRIVE in an iron rich environment.  Those with Hemochromatosis, though, have certain cells that actually lock out iron in them.... macrophages found in their immune system.  These immune cells are the very cells that attack the bacteria that causes the Plague and in effect starves the bacteria to death.  This disorder was also thought to be an advantage to Vikings.  Since the primary treatment for hemochromatosis is "blood letting" to rid the body of extra iron, the Vikings with this disorder would benefit from being stabbed on a regular basis.   They would think of it as well... a treatment of sorts!