On June 3, during ENDO 2024 in Boston, “Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline” was officially released. While this new guideline suggests supplements might benefit specific populations and questions the need for testing, it also suggests that more research is needed to determine optimal levels for specific health benefits.

In the face of the growing popularity of vitamin D supplements in recent years, a new Endocrine Society clinical practice guideline suggests that there is a limited role for vitamin D supplementation and little reason for testing in the prevention of disease.

The guideline suggests supplements be used for specific populations and specific reasons: for children and adolescents ages 1–18 to prevent rickets and potentially lower the risk of respiratory tract infections; for those aged 75 years and older to potentially lower mortality risk; for those who are pregnant to potentially lower the risk of pre-eclampsia and other conditions; and for those with high-risk prediabetes to reduce the risk of progression to diabetes.

It does not recommend a dosage in any of these cases because “the optimal doses for empiric vitamin D supplementation remain unclear for the populations considered.”

The guideline suggests against empiric vitamin D supplementation above the recommended dietary reference intake with the goal of lowering the risk of disease in healthy adults younger than 75 years.

“If you are a healthy adult younger than 75 and taking the dietary reference intake recommended by the Institute of Medicine, which is now known as the National Academy of Medicine, then you don’t need any additional vitamin D if you don’t have risk factors for vitamin D deficiency or increased vitamin D metabolism,” according to Marie B. Demay, MD, of Massachusetts General Hospital and Harvard Medical School, who chaired the committee that wrote the guideline.

“If you are a healthy adult younger than 75 and taking the dietary reference intake recommended by the Institute of Medicine, which is now known as the National Academy of Medicine, then you don’t need any additional vitamin D if you don’t have risk factors for vitamin D deficiency or increased vitamin D metabolism.”

Marie B. Demay, MD, physician, Massachusetts General Hospital; professor of medicine, Harvard Medical School, Boston, Ma.; chair, guideline writing committee, “Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline”  

“We are not saying don’t take vitamin D,” says Anastassios G. Pittas, MD, MS, of Tufts Medical Center in Boston and co-chair of the guideline-writing panel. “We are saying that we did not find evidence that taking additional vitamin D above and beyond the recommended daily allowance would be of benefit in prevention of disease in this age range.”

Questions About Testing

The panel suggests against routine laboratory testing for blood levels of 25-hydroxyvitamin D (25[OH]D) in all the age groups and populations it studied, including adults with prediabetes, dark complexion, or obesity, as well as during pregnancy.

That was in large part because “there really is no data telling us what target vitamin D level should be aimed for to prevent disease,” Demay says.

A 2010 Institute of Medicine expert panel considered a 20 ng/mL (50 nmol/L) serum 25(OH)D concentration to be generally adequate for bone and overall health in the general population, whereas a 2011 Endocrine Society clinical practice guideline said that a concentration of more than 30 ng/mL (75 nmol/L) is needed to maximize the effect of vitamin D on calcium, bone, and muscle metabolism. But the current Endocrine Society panel did not find adequate evidence to confirm these thresholds.

“There is no data that really tells you that a level of 20 ng/mL is fine, or a level of 30 ng/mL is fine,” Demay says. “A big problem is that we don’t have a biomarker for vitamin D adequacy. A second challenge is that the target level may differ for different outcomes.”

A Timely Topic

With so many people taking supplements and having tests for their 25(OH)D levels, Pittas says that it was time for a new guideline because a great deal of clinical trial data has accumulated since the previous Endocrine Society vitamin D guideline more than 10 years ago.

The previous guideline focused on the care of patients at risk for deficiency, whereas this expert panel focused on the use of vitamin D to lower the risk of disease in individuals without established indications for vitamin D treatment or 25(OH)D testing. “These guidelines do not apply to individuals with underlying conditions that substantially alter vitamin D physiology, such as intestinal bypass surgery or inflammatory bowel disease,” Demay says.  

The panel began by identifying the most important outstanding clinical questions that needed answers, and the guideline covers 14 of them, with the questions focusing on whether supplementation or testing for a particular age group or particular population should be recommended. Despite the accumulation of clinical trial evidence, the panel found that the evidence base is still limited when it comes to answering many questions, hence the use of the terminology “suggestions” that the supplements offer “potential” benefits in many uses.

“Most of the large trials over the last decade were done in populations whose vitamin D status at baseline would be considered adequate,” Pittas says. “So, giving a small additional dose of vitamin D may not have an effect because the participants had an adequate vitamin D status for the studied outcomes. This was a key limitation of the included trials that limited the panel to making ‘suggestions,’ which are conditional recommendations according to the GRADE guideline-writing methodology.”

Supplemental Evidence

When vitamin D supplementation is indicated, the guideline recommends daily, lower-dose vitamin D rather than administration of intermittent, higher dose in adults 50 years and older, and did not identify any evidence on the topic for those under 50.

The guideline does not suggest any specific dosages because the panel could not find backing evidence, according to Pittas: “We do not know the optimal vitamin D dose because there is such a wide range of supplementation doses in the clinical trials we looked to for evidence. Treat-to-target trials are needed to establish the most appropriate doses for specific populations and conditions.”

“We are not saying don’t take vitamin D. We are saying that we did not find evidence that taking additional vitamin D above and beyond the recommended daily allowance would be of benefit in prevention of disease in this age range.” 

Anastassios G. Pittas, MD, MS, chief, Endocrinology, Diabetes, and Metabolism; co-director, Diabetes and Lipid Center, Tufts Medical Center; professor, Tufts University School of Medicine, Boston, Ma.; co-chair, guideline-writing panel, “Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline”

The guideline does say that “due to the scarcity of natural food sources rich in vitamin D, empiric supplementation can be achieved through a combination of fortified foods and supplements that contain vitamin D. The panel judged that, in most situations, empiric vitamin D supplementation is inexpensive, feasible, acceptable to both healthy individuals and healthcare professionals and has no negative effect on health equity.”

“Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline” was co-sponsored by the American Association of Clinical Endocrinologists, European Society of Endocrinology, Pediatric Endocrine Society, American Society for Bone and Mineral Research, Vitamin D Workshop, American Society of Nutrition, Brazilian Society of Endocrinology and Metabolism, American College of Obstetricians and Gynecologists, Society of General Internal Medicine, and Endocrine Society of India.

It will be published in the June issue of The Journal of Clinical Endocrinology & Metabolism and is available at: (add a link if one is available at publication time).

Seaborg is a freelance writer based in Charlottesville, Va. In the March issue, he wrote about recent studies that further emphasize the dangers of obesity in adolescence.