A new study published in Lancet Diabetes and Endocrinology used Mendelian randomization to find that high vitamin D levels cause a decreased risk for hypertension.
While randomized controlled trials (RCT) are considered the gold standard for showing causation in clinical vitamin D research, the results can be skewed if the design of the study doesn’t meet important criteria.
To accurately determine whether vitamin D has an effect on a certain health condition, randomized controlled trials need to first recruit participants who have the condition and are deficient in vitamin D at baseline. The trial then needs to administer high, physiological doses for a sufficiently long duration.
Trials that meet these criteria are hard to conduct, but when these trials do meet the criteria, they result in strong findings that accurately depict vitamin D’s role in the health condition being studied.
Mendelian randomization is another method of research that can be used to help show causation.