Short winter days push vitamin D back into conversation every November, along with the question of whether everyone should be taking it. The most detailed answer for healthy adults comes from the Endocrine Society, whose clinical practice guideline on vitamin D for disease prevention was published in The Journal of Clinical Endocrinology and Metabolism in June 2024. It names four groups for supplementation and, for most other adults, advises against going beyond the standard daily intake.

How the guideline was built

The panel, led by Marie Demay, replaced the society's 2011 guidance. It set 14 clinical questions and leaned mainly on randomized, placebo-controlled trials, with systematic reviews and meta-analyses run by the Mayo Clinic Evidence-Based Practice Center through December 2023. Each recommendation was graded with the GRADE system for strength and certainty of evidence. A patient representative sat on the panel.

The scope matters. The guideline covers people without an established reason for vitamin D treatment or testing, and it does not apply to people whose underlying conditions change how the body handles vitamin D.

The four groups it suggests supplementing

Each of these is a conditional suggestion, the softer of GRADE's two levels:

  • Children and teens aged 1 to 18, to help prevent nutritional rickets and possibly lower the risk of respiratory infections. The trials behind this averaged roughly 1,200 IU a day. Certainty of evidence was low.
  • Adults 75 and older, because the trials suggested a possible reduction in deaths. Those trials averaged about 900 IU a day. Certainty was moderate.
  • Pregnant people, for a possible lower risk of preeclampsia, preterm birth and other complications. The trials averaged about 2,500 IU a day. Certainty was low.
  • Adults with high-risk prediabetes, alongside lifestyle changes, to possibly slow the progression to type 2 diabetes. Those trials averaged about 3,500 IU a day. Certainty was moderate.

Those averages describe what the studies used. The guideline does not turn them into a single dose for everyone.

Everyone else: the standard intake is enough

For generally healthy adults under 75, the panel advises against routinely supplementing above the Dietary Reference Intake set by the Institute of Medicine (now the National Academies). That intake is 600 IU (15 micrograms) a day for most adults through age 70 and 800 IU (20 micrograms) after 70, and it can come from food, fortified products or a supplement. The trials did not show added benefit from going higher in this group.

No routine blood test

Perhaps the biggest change is on testing. The guideline recommends against routine blood tests for vitamin D, measured as 25-hydroxyvitamin D, in every population it studied, including adults over 75, pregnant people, and healthy adults with obesity or darker skin. The reason is that no trial established a blood level that prevents disease. The guideline therefore no longer endorses the 30 ng/mL target the 2011 guidance had used.

Daily beats occasional megadoses

For adults 50 and older who do have a reason to take vitamin D, the panel suggests a daily, lower dose rather than large doses taken weekly or monthly. The certainty here is low, but the preference is stated plainly.

What it does not say

The guideline is about preventing disease in people without a diagnosed problem. It does not cover treating diagnosed deficiency, bone disease or conditions that affect vitamin D metabolism, and many recommendations rest on low or moderate certainty evidence. The tolerable upper intake for adults, set by the National Academies and listed by the National Institutes of Health, is 4,000 IU a day, the level above which the risk of harm rises.

What to do with this

The guideline is a useful thing to bring to a checkup: whether you fall in one of the four groups, whether a test is warranted for a specific reason, and how much vitamin D you already get from food and a multivitamin.

This article reports research and expert guidance. It is not medical advice. Talk to your clinician before changing medication, treatment or a medical diet.

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