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BOSTON -- Most healthy adults under 75 can get by with the recommended daily allowance of vitamin D, but some groups should supplement with more, according to a 14-item clinical practice guideline from the Endocrine Society.

Children, people 75 and older, those with high-risk prediabetes, and pregnant people should take "empiric supplementation" of vitamin D exceeding the (DRI) allowance, experts said at ENDO 2024, the annual meeting of the Endocrine Society.

But, based on the absence of supportive clinical trial evidence, the guideline's expert panel suggested against routine 25(OH)D testing in the absence of established indications, in a paper published in .

Established by the Institute of Medicine, the DRI is set at 600 IU or 15 μg daily for most children and adults.

"These guidelines are to address vitamin D requirements for disease prevention in healthy adults who have no underlying conditions that would put them at risk of impaired vitamin D absorption or action," noted guideline co-chair Marie Demay, MD, of Harvard Medical School and Massachusetts General Hospital in Boston.

For the guideline, the panel searched published research, with an emphasis on clinical trials, related to 14 clinical questions surrounding vitamin D, 25(OH)D testing, and disease risk reduction. The group found:

• Vitamin D supplementation in adolescents ages 1 to 18 is aimed at preventing nutritional rickets and to lower the risk of respiratory tract infections (based on low evidence). Underpinning clinical trials used doses ranging from 300 to 2,000 IU (7.5 to 50 μg) daily equivalent for this benefit, with an average of about 1,200 IU (30 μg) per day.
• In adults 75 and older, extra vitamin D has been tied with reduced mortality risk (moderate evidence). For this benefit, trials used a range from 400 to 3,333 IU (10 to 83 μg) daily equivalent, with an average of 900 IU (23 μg) daily.
• Extra vitamin D may help reduce progression to full-blown diabetes in people with high-risk diabetes (moderate evidence). Vitamin D dosages in clinical trials ranged from 842 to 7,543 IU (21 to 189 μg) daily equivalent, with the average being approximately 3,500 IU (88 μg) per day. Participants in some trials were allowed to remain on their routine supplements, including up to 1,000 IU (25 μg) of vitamin D daily.
• Empiric supplementation also may help lower the risk of preeclampsia, intra-uterine mortality, preterm birth, small-for-gestational-age birth, and neonatal mortality in pregnant people (low evidence). Clinical trial doses ranged from 600 IU to 5,000 IU (15 to 125 μg) daily equivalent, usually provided daily or weekly. The average was approximately 2,500 IU (63 μg) per day.

"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," the guideline authors wrote.

In non-pregnant adults older than 50 for whom vitamin D is indicated, the guideline suggested daily, lower-dose vitamin D instead of non-daily, higher-dose vitamin D (low evidence). The guideline also recommended against empiric vitamin D supplementation under age 50 (very low evidence) and against routine vitamin D supplementation in ages 50-74 (moderate evidence).

The guideline advised against routine 25(OH)D testing in the following populations, all supported by "very low evidence":

• All ages (under 50, ages 50-74, and 75+)
• During pregnancy
• Adults with dark complexions
• Adults with obesity

"There is no single question or answer about vitamin D," said co-chair Anastassios Pittas, MD, of Tufts Medical Center in Boston. "We physicians get this question a lot -- 'what should I do about vitamin D?' -- and I don't know how to answer that question. There are many questions and the panel could not possibly answer all of them, so we identified 14 questions that we thought were clinically relevant about the role of vitamin D in prevention of disease."

The clinical practice guideline was co-sponsored by the American Association of Clinical Endocrinology, the European Society of Endocrinology, the Pediatric Endocrine Society, the American Society for Bone and Mineral Research, the Vitamin D Workshop, the American Society of Nutrition, the Brazilian Society of Endocrinology and Metabolism, the Society of General Internal Medicine, and the Endocrine Society of India.

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