With the development of greater understanding for the many vitamin D areas of influence, is there a level of the passive D form 25OHD3 that is best, including cancer protection? The vitamin D experts of today seem to be of the mindset that much greater levels than the currently recommended 600 IUs intake (and 20 -30 ng/ml) are needed to build up the blood levels to the 40+ ng/ml levels which some nutritionists are recommending is needed for cancer reduction. 
Since toxic reactions do not show up until 20,000-40,000 IUs taken over time, some experts are recommending 5000, even 10,000 IUs as safe and necessary. This could generate ng/nl levels well over 50 and even up to 90 or 100 ng/mL (nanograms per millilter). 100 ng/ml would be 250 nmol/L (nanomoles per liter). Some people exhibit a resisitance to storage form vitamin D build up, possibly a gene change.
NOTE: Additional research results insight is pointing to vitamin D supplements as helpful if you are low, BUT at higher beginning levels, taking extra can turn from beneficial to harmful and increase certain cancer risks or cardiovascular links to artery calcification, plus prostate risks need to be evaluated. These points are being missed by some nutritionists. GET tested before you supplement dosages higher than 2500 IUs, especially for extended periods of time. ref <in kidney disease ---
The concern is not over vitamin D toxicity, but about the possibility of influencing Calcium activities in a negative way. Or possibly it could be due to an interference of the passive D form blocking out the attachment of the active hormone form to vitamin D receptor sites (VDR). Not all research at this time is on the side of these vitamin D experts. Below are some of the associations from research that need to be answered before larger D dosages should be routinely consumed plus that question going over 40ng/ml, which might be nature's average limit for 25 OHD, the storage form of passive D. ref
- Dr Martha Booth, a neurologist at Duke University, found than higher blood levels of calcium and vitamin D were the only two variables after various adjustments that were positively associated with greater size and numbers of brain lesions verified by MRI pictures. Vascular lesions such can be associated with calcification of brain blood vessels or due to mini-strokes causing brain cell damage. A weakened vessel wall from faulty nutrition to maintain collagen and ellastin integrity could also be a factor.
- The NHANES study did not find that 25OHD status was related to overall mortality risks except in men, were an elevated risk at higher levels was found. (Could mostly be from prostate and lung cancers)
- For women, while non significant overall, risks were decreased for women in summer living at higher latitudes.
- In a subset of people who exhibit a B allele modification, a gene controlling artery calcification, higher vitamin D might put them in greater jeopardy by increasing calcium blood levels.
- One of the methods used to verify that 10,000 IU is safe and equal to full sun production of about 20 minutes is flawed. The research used vitamin D2 which is only at best 50% of the activity level of vitamin D3. It probably is only 30% over time. This would mean the safe level for vitamin D3 is only 3000 IUs and not 10,000, at least using this method. (This could mainly be due to longer lasting effects of vitamin D3 and not from the quick results of equal doses.) Look at Conclusion in this ref ref ref
- Sun produced vitamin D has a failsafe mechanism also induced by sunshine that acts as a feedback loop to control how much of the sun produced non-active vitamin D3 actually gets added to the circulating D pool. Some is destroyed. This mechanism does NOT let passive D levels get too high. Supplemental vitamin D does not exhibit this feedback loop and can get higher than the body would naturally produce.
- A new Fragility study to determine the vitamin D levels associated with the least fragility symptoms in Seniors found that the best levels were between 20-26 ng/ml, with both under 15 and over 30 having greater adverse effect symptoms.
- While Dr Giovannucci found a protective effect from higher vitamin D levels against cancer in the large Health Professionals Follow-Up Study, these intake levels were only 600 IUs or greater versus 150 or less, not the mega dosage D supplements of 2500 - 10,000 that have recently become available.
- One potential risk of increasing vitamin D intake; if conditions already exist for placing calcium in artery lesions, more vitamin D might accelerate this effect by increasing calcium blood levels, although this has not always been observed.
- Here is a Middle Eastern study that compares different load level vitamin D supplement protocols on blood storage D build up. since D is often low without sun exposure, most effective and safe protocol is to take 2000 IUs for 3 months and then maintain at 1000 IUs. 225% increase. ref
ARE THE (VITAMIN D) EXPERTS wrong again?