Common problems with Vitamin D clinical trials – Grassroots Health – 2019

From: How do you know what to believe about vitamin D?

Common Problems

1. 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.
2. 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.
3. No initial serum measurement – you can’t measure change if you don’t know the starting value.
4. 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.
5. Low dosing (under 2,000 IU/day) – may not move nutrient status significantly for enough of the study participants to observe any effect.
6. 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.
7. 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.
8. 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.