VITAMIN D AIN’T WHAT IT’S CRACKED UP TO BE

It wasn’t long ago that researchers and clinicians thought vitamin D was the secret to a healthy life. A lot of physicians believed that a low level of vitamin D was the underlying cause of many common disorders “including musculoskeletal, metabolic, cardiovascular, malignant, autoimmune, and infectious diseases.” I even heard a U.S. Naval officer doing research on vitamin D say it was the “next big thing,” and it was going to change medicine for the better. There were even allegations it was involved in causing some cancers. 

I attended several lectures on the benefits of vitamin D, and listened to doctors praise the discovery of something so readily available and so safe that patients could buy it over-the-counter. It had positive effects on the immune system, and low levels of vitamin D were associated with increased risk of autoimmune disorders such as psoriasis, Type I Diabetes, Multiple Sclerosis, Rheumatoid Arthritis, Tuberculosis, sepsis, respiratory infections, and COVID-19. Because it has anti-inflammatory properties, it was thought vitamin D “may reduce the incidence of major cardiovascular events” (eg. Heart Attack, Stroke).” Later studies, however, found it did not. You can imagine how excited doctors were about the prospects of vitamin D being a cure, or adjunct, in the treatment of many devastating disorders. That was the thought until now.

Further study has not shown the presumed association of vitamin D and chronic disease. In fact, a “causal link between low vitamin D…..and many disorders has not been clearly established.” There are still a lot of patients who have vitamin D blood levels done regularly, and who take supplemental vitamin D daily. But despite all of this, there remains “uncertainty surrounding the optimal level of vitamin D required to prevent disease,” if it really does.

It is still, though, indicated for adults older than 75 years, adults with high-risk diabetes, pregnant women (the reference says pregnant “people”), and children. The reasoning is that in older adults, vitamin D “lowers mortality risk.” In people with diabetes, vitamin D “reduces the progression of diabetes.” In pregnancy, it reduces the risk of pre-eclampsia, intra-uterine mortality, pre-term birth, and low birthweight infants. In children, vitamin D prevents rickets, a bone disease caused by dietary deficiency of vitamin D. 

Experts recommend AGAINST routine testing for vitamin D. They are unable to determine specific blood levels of vitamin D that indicate vitamin D is needed for disease prevention. “There is a paucity of data regarding definition of optimal levels and optimal intake of vitamin D for preventing specific diseases….we have no data that…screening…allows us to improve quality of life.”

So, over the past 20 years, medical science has gone from thinking that low levels of vitamin D were the key to the cause and progression of chronic disease to where routine testing is not recommended. No causal link between vitamin D and chronic disease has been proven. The blood level of vitamin D below which patients are at risk of chronic disease has not been determined. And the optimal dose of vitamin D for disease prevention has also not been determined. 

The important statement here is that it’s more pertinent to focus on control and stabilization of a chronic disease itself than it is to expect vitamin D to moderate the problem. A cause, effect, and benefit profile for chronic diseases has not included the use of vitamin D. Thus, vitamin D, despite the past lofty assertions that it was the foundation for many human medical disorders, has not proven to be “what it was cracked up to be.” It’s OK to take it, but don’t expect it to lengthen your life or protect you from dying.

Reference: Endocrine Society guideline recommends healthy adults under the age of 75 take the recommended daily allowance of Vitamin D. Medscape Medical News 2024.

Tucker M. Don’t screen for Vitamin D: New Endo Society Guideline. Medscape Medical News 2024 June 3:1-5. 

Demay MB, et al. Vitamin D for the prevention of Disease: An Endocrine Society Clinical Practice Guideline J Clin Endo Met 2024 June 3;109:1907-1947.

Subramanian S, Griffin G,et al. Vitamin D and CIVID-19-Revisited. J Int Med 2022 Oct;292(4):604-626.