Watching this You-Tube video from the University of California at San Diego might be one of the best things you can do for your health. It explains clearly and in detail which levels of vitamin D3 are necessary to prevent a great variety of diseases. Rickets, the disease our woefully inadequate RDA was designed to prevent, needs very little Vitamin D. Cancers, diabetes, heart attack, falls, fractures, hypertension, neurological impairment, even pain will be prevented by raising your blood Vitamin D levels to the recommended range.
I have been taking 10,000 iu of Vitamin D3 daily for the last year and am only in the low end of the recommended range.
You can find the charts shown in the video at http://www.grassrootshealth.net
A blood level of Vitamin D (have your doctor test it) should be 40-60 ng/ml, which is likely higher than the reference range of the test. You would need to reach 200 ng/ml to suffer from toxicity. The amount you need to supplement will vary, but is way way higher than you find in any multi. Unless you seek out a special high concentration vitamin D supplement, you are not getting enough, at least above the Mason-Dixon line (and usually below as well.)
This video puts together the Vitamin D research and offers a public health program designed to raise Vitamin D3 and calcium to levels that would prevent 58,000 new cases of breast cancer and 49,000 new cases of colorectal cancer annually in the US and Canada within the next five years. The researchers model also predicted that 75% of deaths from these cancers could be prevented with adequate intake of vitamin D3 and calcium.
In Finland, in the 1960s, mothers gave babies 4500 iu of Vitamin D daily. When the dosage was lowered to 2000 iu, type 1 diabetes rates began to rise and when the dosage was lowered to 400 iu, the level we usually find in a US multi-vitamin, type 1 diabetes skyrocketed. With sufficient supplementation during pregnancy and early childhood you can prevent 8/10 cases of type 1 diabetes. You will rarely find the higher level of Vitamin D recommended for children in the US because we have only focused on the association of Vitamin D and rickets.
Vitamin D helps maintain tight junctions between cells so that signaling is better and viruses or other infectious agents cannot get in between the cells. Some of those agents will trigger autoimmune reactions.
The chart linked below shows why higher doses are needed for cancer, type 1 diabetes, MS, and a variety of other diseases than rickets- the MDR was based on preventing rickets which responds well enough to low doses of vitamin D. Note that 35% of all cancers were prevented with at a level of 1000 iu daily, giving a blood level of 38 that is below the recommended range -perhaps much higher prevention would be found if they had tested higher ranges. Most disease tested were prevented in the 40-60 range, with toxicity not found below 200. It is all based upon good research: