How a 2019 NEJM Study (VITAL) Misled the World on Vitamin D

Snippits

"But there is a foundational problem: most participants weren’t vitamin D deficient to begin with. Only 12.7% had levels below 20 ng/mL, the threshold generally associated with increased risk. The mean baseline level was 30.8 ng/mL—already at or near sufficiency. It’s the equivalent of testing whether insulin helps people who don’t have diabetes."
"Further eroding the study’s contrast, participants in the placebo arm were allowed to take up to 800 IU/day of vitamin D on their own. By year 5, more than 10% of the placebo group was exceeding that limit. The intervention, in effect, became a test of high-dose vitamin D versus medium-dose vitamin D, not against a true control."

Only 6% of the participants had their end-of-trial vitamin D levels measured (approximately $50 for each quantitative test = too expensive)

Was worried that the VITAL trial would set back research by at least 5 years
It appears that vitamin D research funding has decreased by about half recently (perhaps due to poor results of the VITAL trial)