If a healthy person has a few minutes of sun exposure each day, we wouldn't need extra Vit D, that is correct. However, this does not take into account all those on Statin Drugs.
STATINS, CHOLESTEROL, VITAMIN D
Statins block HMG-CoA Reductase which is a liver enzyme which is a key enzyme in the production of the Cholesterol molecule (NOT HDL or LDL). Cholesterol is a key molecule in all cell membranes, especially the brain which is incorporated in the lipid bilayer of cell membranes and the Endoplasmic Reticulum to maintain membrane fluidity. By the way, if you are Cholesterol deficient (egg yoke molecule not LDL or HDL), then your ER gets too stiff, and key enzymes that are incorporated in the ER that are continually inserted, cut out, and replaced, get cleaved in the wrong place and fail to get transported to the lysosome and then the peroxisome thus building up as plaque in the cell. Then you get nonspecific iron binding, then Fenton Chemistry/Haber-Weiss reaction, then free radical production, lipid peroxidation, and cell death.
CHOLESTEROL, HORMONES, CORTISOL, VITAMIN D
Cholesterol is a key intermediate in the formation of sex hormones, cortisol which regulates the immune system and vitamin D. So, if you are blocking the synthesis of Cholesterol, it doesn't matter how much sun you get. You can be in the sun all day, and if you don't have the pro-vitamin, your body cannot use the sun to create the active Vit D molecule.
VACCINES AND ADUVANTS
This doesn't take into effect all those who have received avian flu or anthrax vaccines which contained Squalene as a vaccine adjavant. Adjuvants are molecules added to vaccines to rev up the immune system, and illicit a stronger immune response against the weakened target virus or bacterial protein. Squalene is not a good adjuvant at all by itself. It is only active as an adjuvant after being covalently bonded to an immunogenic surfactant (detergent).
SQUALENE AND VITAMIN D
While adjuvants are a good idea, the important thing to remember is that in the process of revving up the immune system, antibodies are produced to the target viral protein as well as the adjuvant that is doing the immunogenic stimulation. The big problem with Squalene is that, it is found in the body. It just so happens that Squalene is a key intermediatary in the formation of . . . . . .. you guess it. . . . . Cholesterol. So, many people exposed to the avian flu vaccine and anthrax vaccine may have anti-Squalene antibodies, and consequently, may be deficient in not only Cholesterol, but also, Sex Hormones, Cortisol, and Vitamin D.
STEPS IN CHOLESTEROL SYNTHESIS PATHWAY
HMG-CoA Reductase ->->-> Squalene ->->-> Cholesterol ->->-> Sex Hormones, Cortisol, Vitamin D.
CHOLESTEROL VS. LDL?
By the way, Vitamin D is not a vitamin it is a Hormone that does much more in the body than regulate bone synthesis. I used to ask myself why there was confusion between the good molecule Cholesterol, and HDL and LDL. Why do we use the word Cholesterol when talking about Lipoprotein. I could never figure this out. This confusion has led many to erroneously eat eggs without the yoke. Before you go crazy on egg yokes, the liver makes many times more cholesterol each night then you could get out of egg yoke. Well, after reading Protocol of Zion, Silent Weapons for a Quiet War, Report from Iron Mountain, I now suspect the confusion and vilification of Cholesterol was done on purpose. You attack Cholesterol, you make us sterile, sick, and mentally deficient.
I've enjoyed reading the blog http://blog.cholesterol-and-health.com which discussed the goodness of cholesterol, the badness of fructose and sucrose, and suggests interesting ideas like using allopurinol to increase NO and lower uric acid and blood pressure.