A person can have a high level of vitamin D in their blood stream,

but the cells might not get much benefit from it - due to:

1. Kidney problems
2. Vitamin D not converted well in other areas of the body (besides the Kidney): gene problems
3. Low level of Magnesium - which is needed by the cells to utilize Vitamin D
4. Low level of other Vitamin D cofactors, such as Calcium - especially needed for muscular-skeletal problems
5. Vitamin D receptors in cells are working poorly

Just as with Magnesium and Calcium, the vitamin D level in the blood is easily measured, but results can give a wrong impression

Far better to measure the level in the cell - but extremely expensive

You might have a good level of vitamin D in the blood (say 40 - 50 ng),

but genes and lack of cofactors might prevent your getting the benefit of vitamin D,

all around your body, or in the case of some genes, just certain body locations

For the health problems which take a long time to develop, such as cancer,

You could have 40-50 ng of vitamin D in the blood but would have little or no indication that

1. your kidney was not functioning well
   OR
2. gene was malfunctioning, not notice until it was too late

A guess: 30% of the population will not get all of the benefits of vitamin D in their blood

Solution, while waiting for low cost DNA tests, get a higher level of vitamin D - perhaps 80 ng
https://www.23andme.com has low cost DNA tests. Their very simple test has dropped to $99 as of March 2013
Nice Interview of 23andMe CEO on Medscape June 2014 video and transcript

1. Take more vitamin D supplements
2. How you might double your response to vitamin D can get 2X more response for the same amount of supplement
3. Get more UVB at home
4. Optimize vitamin D from the sun

See also VitaminDWiki

• Hypothesis – Receptor activation more important than vitamin D levels – June 2011
• Google Search for VitaminDWiki for VDR activtaion 316 hits March 2013
• All items in category Genetics 344 items
• GC, CYP2R1 and DHCR7 genes associated with low vitamin D levels in China – 2012, 2013
• Mutations in CYP24A1 gene (vitamin D) associated with kidney problems – Jan 2013
• How Vitamin D prevents many cancers (c-MYC) – Nov 2012
• Calcium and vitamin D receptors are important to many health conditions – Jan 2013
• County with 20 pcnt higher breast cancer rate has 2X more modified vitamin D receptor – July 2012
• Epigenetics, vitamin D, and Multiple Sclerosis
• Genes such as CYP27B1, CYP24A1 and Vitamin D – JAMA Nov 2012
• CYP24A1 gene, kidney disease, and vitamin D - May 2011
• 3X higher risk of oral cancer if CYP27B1 and CYP24A1 genes were different – May 2012
• Genetic Disorders and Defects in Vitamin D Action PDF file
• Genes breast cancer and vitamin D receptor - Sept 2010
• Vitamin D Receptor genes bb and BB and Osteoporosis, esp. for blacks – meta-analysis Nov 2012
• Melanoma and Vitamin D genes - multiple papers
• Low cost vitamin D Blood Tests Note: this tests vitamin D in blood, not inside of cells
• Overview Vitamin D Dose-Response
• Reasons for low response to vitamin D
• Vitamin D3 becomes Calcidiol which becomes Calcitriol
• Active level of vitamin D are not indicated by standard blood tests - Sept 2012
• Possible ways that vitamin D does its magic
• Calcitriol, not inactive vitamin D, associated with pain in seniors – Aug 2014
• Vitamin D reduced so low that Victorian age diseases are returning which has the following graphic