 Most selfnews readers know some of the health values of vitamin D3, which go well beyond the accepted bone health quality. But how much is enough and how little is not enough is a controversial subject. Adding to the confusion is some concern of how much would lead to excessive vitamin D3 intake to produce the rare event of vitamin D toxicity. Vitamin D3 toxicity from skin exposure to sunlight or UVB (ultraviolet B) tanning beds is normally impossible. The process of epidermal cholesterol converting the UVB rays into the vitamin D3 precursor, cholicalciferol has the built in feature of slowing or stopping that process if too much vitamin D3 starts accumulating in your blood. That cholicalciferol is converted in a two stage process by first the liver then the kidneys to create the active vitamin D3 hormone calcitriol . Even large doses of vitamin D3 supplements have rarely caused a toxic reaction. But because vitamin D3 supplements are fat soluble, the toxic effects can linger longer than other toxic events. However, only three cases of vitamin D toxicity have been recorded, and they were supplementing over 40,000 IUs (international units) daily. Most doctors and nutritional experts recommend having 25(OH)D testing done to determine your vitamin D3 blood levels while supplementing 1000 to 5000 IUs of vitamin D3 supplements daily. Vitamin D3 supplements contain cholicalciferol, taken from the lanolin of sheep's wool after shearing. The cholicalciferol that is normally produced by the interaction of UVB sun rays with a form of cholesterol in our skin is encapsulated in those supplements. The convenience of supplements bypasses our body's automatic safeguard feature that limits the conversion of UVB rays forming cholicalciferol, which our livers and kidneys then use to manufacture vitamin D3. Regardless, toxicity is very rare. Recent study sets a positive health vitamin D3 threshold lower than most savvy experts A Washington University study recorded May 1st, 2012 in the Annals of Internal Medicine by Dr. Ian de Boer, resulted in a minimum D3 blood level vitamin that merely duplicates mainstream medicine's recommendation. Dr. de Boer's research team used 25(OH)D test data on stored blood samples from older adults who had enrolled in a nationwide cardiovascular health study from 1992 to 2006. They did a statistical follow up on major medical events these older adults had incurred and compared them to the D3 blood counts. Their study on 1,621 senior citizens concluded that 20 ng/ml (nano-grams/milliliter) in blood serum is the cutoff point. In other words, below 20 ng/ml in blood serum invites seriously worsening health. This is exactly what mainstream medicine considers as the minimum vitamin D3 level to ward off major disease. As we age, the process of converting sunlight to D3 wanes, and there are many who disagree with the study's recommendation. Experts consider mainstream vitamin D3 threshold for health too low for optimum health The Vitamin D Panels nutritionally qualified members consider the recommended doses of D3 supplementation of no more than 800 IUs way too low for eliminating D3 deficiencies. So do many other experts. They've also determined a higher threshold of blood serum levels for optimum health . Another study of D3 blood serum level samples among extremely healthy inhabitants of tropical and sub-tropical areas showed blood serum levels of D3 between 50 ng/ml and 70 ng/ml. Under 50 ng/ml is considered D3 deficient by many experts who strive for optimum, preventative health instead of determining what levels guarantee hospitalization. Caveat: People afflicted with tuberculosis, lymphoma, or sarcoidosis should use the 1,25(OH)D test instead of the 25(OH)D test before supplementing D3. You'll find several vitamin D3 articles here: http://www.selfnews.com 