Healthy adults under the age of 75 are unlikely to benefit from taking more than the daily intake of vitamin D recommended by the Institutes of Medicine (IOM) and do not require testing for vitamin D levels, according to a new Clinical Practice Guideline issued today by the Endocrine Society. For children, pregnant people, adults older than 75 years and adults with high-risk prediabetes, the guideline recommends vitamin D higher than the IOM recommended daily allowance.

Vitamin D use and blood vitamin D levels have been associated with many common diseases. However, whether vitamin D supplementation lowers the risk of these diseases and what vitamin D blood levels are needed for better health have been debated for years.

In this new guideline, the panel of experts established guidelines for vitamin D use and testing for vitamin D levels in healthy persons without established indications for vitamin D treatment or testing. The guideline relied on clinical trials to develop the recommendations.

The guideline, titled "Vitamin D for the Prevention of Disease: An Endocrine Society Clinical Practice Guideline," was published online and will appear in the August 2024 print issue of The Journal of Clinical Endocrinology & Metabolism (JCEM), a publication of the Endocrine Society.

"The goal of this guideline was to address the vitamin D requirements for disease prevention in a generally healthy population with no underlying conditions that would put them at risk of impaired vitamin D absorption or action," said Marie Demay, M.D., of Harvard Medical School and Massachusetts General Hospital in Boston, Mass. Demay is the chair of the panel that developed the guideline. "Healthy populations who may benefit from higher dose vitamin D supplements are those 75 and older, pregnant people, adults with prediabetes, and children and adolescents 18 and younger, but we do not recommend routine testing for vitamin D levels in any of these groups."

Key recommendations from the guideline include:

• We suggest against vitamin D supplements at doses beyond the reference dietary intakes recommended by the IOM in healthy adults under 75 years old.
• We identified the following populations that may benefit from supplementation above the intakes recommended by the IOM because of the potential to reduce specific health risks:
  • Children and adolescents 18 and younger -- potential to prevent nutritional rickets and to reduce the chance of respiratory infections.
  • Individuals 75 and older -- potential to lower mortality risk.
  • Pregnant people -- potential to reduce risk of pre-eclampsia, intra-uterine mortality, preterm birth, small-for-gestational age birth and neonatal mortality.
  • People with prediabetes -- potential to reduce progression to diabetes.
• In adults ages 50 years and older who have indications for vitamin D supplementation or treatment, we suggest daily, lower-dose vitamin D instead of non-daily, higher-dose vitamin D.
• We suggest against routine testing for 25-hydroxyvitamin D levels in any of the populations studied, since outcome-specific benefits based on these levels have not been identified. This includes 25-hydroxyvitamin D screening in people with dark complexion or obesity.

Even though the evidence on the role of vitamin D in health and disease has increased over the last decade, the panel noted many limitations in the available evidence. For example, many of the large clinical trials were not designed for several of the outcomes that they reported, and the studied populations had vitamin D blood levels that most would consider adequate to begin with. Based on insufficient evidence, the panel could not determine specific blood-level thresholds for 25-hydroxyvitamin D for adequacy or for target levels for disease prevention.