Overview Meta-analysis of Vitamin D

Unfortunately, a meta-analysis will frequently fail to consider one or more of the following

1. Dose size (Some gave the same importance to 40 IU as 10,000 IU)
2. Dose frequency (Some ignore differences between daily, weekly, monthly, and annual dosing)
3. Duration, (Some gave same importance to 4 weeks as 4 years)
      It takes 3 to 12 months for vitamin D levels to come to a new plateau
      and it often takes months for the body to then utilize it
4. Pre-existing Vitamin D blood level
      adding vitamin D does not provide much benefit if person alrady has a good level
5. Cofactors (Most meta-analyses ignore the importance of Magnesium, Omega-3, Vitamin K2, etc)
6. Type of Vitamin D - D3 far better than D2
7. Those with poor guts need a different type of vitamin D
8. Those who are Obese need 2.5 X more vitamin D
9. Many drugs, such as statins deplete vitamin D or the Magnesium needed by Vitamin D
10. For some health problems pulsed vitamin D, not daily, is far better (gets over possible Vitamin D receptor limitation)

All items in category Meta-analysis and Vitamin D 665 items

Vitamin D Global Perspective - Holick June 2013 has the following summary table

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Meta-analyses of 50+ disease categories in VitaminDWiki