50% of the control group (13 people) required admission to the ICU. Only 2% of those in the vitamin D group (one person) required admission to the ICU.
Expressed as relative risk, vitamin D reduced the risk of ICU admission 25-fold. Put another way, it eliminated 96% of the risk of ICU admission.
These results are consistent with the first observational study on vitamin D, which found that 96% of severe and critical cases occurred at 25(OH)D under 30 ng/mL, whereas 97.5% of mild cases had 25(OH)D above 30 ng/mL.
This study couldn’t measure the effect on mortality, but all two deaths were in the control group and the near abolition of ICU risk suggests that death would also be nearly abolished. This is consistent with the second observational study finding that only 4% of those with vitamin D status above 30 ng/mL died, while 88% of those with vitamin D status at 20-30 ng/mL died, and 99% of those with vitamin D status lower than that died.
This was statistically significant at p<0.001, and the 95% confidence interval was 0.002-0.17. This means that the probability of observing differences this large or greater if there is no true effect of vitamin D is less than one in a thousand, and that the probability is 95% that the true effect lies somewhere between an 83% and a 99.8% reduction in the odds of ICU admission.
The vitamin D was provided as oral calcifediol, also known as calcidiol, 25(OH)D, and 25-hydroxyvitamin D. This is a metabolite of vitamin D that our livers make. It is is the principle form of vitamin D that circulates in the blood, and we use it as a measure of vitamin D status.
Traces of 25(OH)D occur in food, and it is five times as potent as vitamin D. As described on page 255 of the 1997 DRI Report, 25(OH)D is given an international unit (IU) value that equates it to vitamin D. Whereas one microgram (mcg) of vitamin D is 40 IU, 1 mcg of 25(OH)D is 200 IU.
The treatment in this RCT was soft capsules of 532 mcg 25(OH)D on day 1 of admission to the hospital, followed by 266 mcg on days 3 and 7, and then 266 mcg once a week until discharge, ICU admission, or death.
This is equivalent to 106,400 IU vitamin D on day 1, 53,200 IU on days 3 and 7, and 53,200 IU weekly thereafter. If this were given as daily doses, it would be the equivalent of 30,400 per day for the first week, followed by a maintenance dose of 7,600 IU per day.
The vitamin D status of the patients was not measured. However, the average vitamin D status in this region of Spain during the time of year in which the study was conducted is 16 ng/mL. A single dose of 100,000 IU vitamin D tends to raise a 25(OH)D of 10 ng/mL into the 20-30 ng/mL range. My suspicion is that the bolus dosing in the first week brought the patients’ vitamin D status into the 30-40 ng/mL range by the end of the week, and that most of the healing took place in the circa 40 ng/mL range.