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Evidence remained insufficient to support broad screening for vitamin D deficiency in adults, the U.S. Preventive Services Task Force (USPSTF) said.

As it did , USPSTF determined that the lack of direct evidence precluded the assessment of the balance of benefits and harms of routine screening in asymptomatic, community-dwelling adults.

Detecting vitamin D deficiency itself poses several challenges in particular. It is possible that 25(OH)D -- the major circulating form of vitamin D -- may not be the best measure of deficiency, and vitamin D requirements may vary by sex and race, according to Alex Krist, MD, MPH, of Virginia Commonwealth University in Richmond, and colleagues in .

"Before we can know if screening for vitamin D deficiency helps prevent negative health outcomes such as falls, cancer, or heart problems, we need to understand the level of vitamin D that is too low," said USPSTF member John Wong, MD, of Tufts Medical Center in Boston, in a press release. "Once the ideal level of vitamin D is identified, then research on whether screening for vitamin D deficiency can improve health outcomes will be helpful."

USPSTF cautioned that it did not review the emerging evidence on vitamin D and COVID-19 outcomes.

The recommendation statement was based on a 46-study systematic review, also published , that suggested treatment with vitamin D to have no effect on mortality or the incidence of fractures, falls, depression, diabetes, cardiovascular disease, cancer, or adverse events.

There is also no evidence that low blood levels of vitamin D directly cause poor health outcomes, commented Jodi Segal, MD, MPH, of Johns Hopkins University School of Medicine in Baltimore, and colleagues in a .

"[L]ow 25(OH)D status might reflect a poorer health status in general owing to reverse causation or confounding by other health or behavioral factors," they wrote. "Even the benefit of vitamin D on bone health and musculoskeletal outcomes has been challenged, and its efficacy may depend on whether concomitant calcium supplementation is given."

"Over the past 7 years, despite RCTs of vitamin D supplementation, everything has changed and yet nothing has changed regarding the approach to screening for vitamin D deficiency," Segal's group concluded.

For now, clinicians may choose not to measure vitamin D levels and to ensure that all individuals consume the age-based recommended daily allowance of vitamin D, according to Sherri-Ann Burnett-Bowie, MD, MPH, of Massachusetts General Hospital and Harvard Medical School, and JAMA associate editor Anne Cappola, MD, ScM, of Perelman School of Medicine at the University of Pennsylvania.

People at increased risk for vitamin D deficiency "could be empirically prescribed a higher dose of vitamin D (e.g., 2000 IU/d) that is still below the upper daily limit," they wrote in an .

Notably, the USPSTF statement applies to screening people with no signs of vitamin D deficiency or conditions requiring vitamin D treatment -- not those with existing bone pain or muscle weakness, or others at presumed risk.

"Approximately half of adults would be considered vitamin D deficient or insufficient using current definitions, with higher rates in racial/ethnic minorities, including Black and Hispanic individuals, suggesting wide-spread vitamin D deficiency," Segal and colleagues said.

They noted that the harms of telling asymptomatic people that they are vitamin D deficient could include patient anxiety, costs of treatment for vitamin D repletion and monitoring, the pill burden of supplementation, and toxicity from overtreatment.