From: How do you know what to believe about vitamin D?
Common Problems
- Bolus dosing (generally large, intermittent dosing) – immune function only improves with daily dosing of vitamin D. Yet many studies on muscular/skeleton hypothesis were very effective on bolus (weekly, monthly) dosing.
- Hypothesis/goal does not mention change in nutrient status – this premise will be the core problem with items 4-6 below. Since vitamin D synthesis varies greatly for each person, the hypothesis cannot be by treatment amount (supplement intake) but instead needs to be investigated around achieving a certain serum level.
- No initial serum measurement – you can’t measure change if you don’t know the starting value.
- Participants are not deficient (<20 ng/ml) at the start – see Dr. Grant’s comment below. Since an effective study would change nutrient status significantly, the study needs at least one group to start at the low end.
- Low dosing (under 2,000 IU/day) – may not move nutrient status significantly for enough of the study participants to observe any effect.
- Analyzed only by dosage/treatment group, not by serum level – we need to know what serum level our patients should achieve for the desired effect.
- Less than or equal to 6 months testing for chronic conditions and disease prevention – as Dr. Holick says so eloquently below, it takes time to change nutrient levels within the body.
- No mention of co-nutrients, no attempt to optimize co-nutrients – this criteria is not a reason to throw out the study, but it would be optimal to optimize co-nutrients.
Below, some of the GrassrootsHealth Panel of Scientists speak to what they deem are some of the most important of the Heaney criteria.