Kenneth W. Lin, MD, MPH

DISCLOSURES | February 04, 2025

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Hi, everyone. I’m Dr. Kenny Lin. I am a family physician and associate director of the Lancaster General Hospital Family Medicine Residency, and I blog at Common Sense Family Doctor.Kenneth W. Lin, MD, MPH

I recently went to my local pharmacy to pick up a prescription and happened to find myself in the vitamin aisle. Standing in front of the sizable section devoted to vitamin D supplements, I faced a bewildering array of tablets, capsules, softgels, and gummies in daily doses ranging from 400 to 10,000 international units. The store was obviously doing a brisk business. Who was buying and consuming all of this vitamin D, I wondered, given the limited proof of its health benefits?

There have historically been two clinical approaches to vitamin D supplementation in adults: (1) Check blood levels of vitamin D and supplement those who are “deficient” (less than 20 or 30 ng/mL, depending on whom you ask); or (2) Give a standard dose of vitamin D to everyone of a certain age or in a defined population. 

The US Preventive Services Task Force (USPSTF) examined the former approach in 2021 and found insufficient evidence that assessing vitamin D status and treating vitamin D deficiency improved any outcomes. Last year, the Endocrine Society chose the latter strategy in recommending routine supplementation for children, adults older than 75 years, pregnant patients, and adults with prediabetes, but I felt that the only convincing case was supplementing to reduce mortality in older adults. 

(Those recommendations caused significant controversy, with many clinicians saying they would ignore them when Medscape reported on their release in June).

In December 2024, however, the USPSTF posted a draft update to its 2018 guideline on vitamin D and calcium supplementation that recommends discouraging community-dwelling adults age 60 years or older from taking vitamin D supplements (with or without calcium) to prevent fractures or falls. The basis for this “don’t do” recommendation is a draft evidence synthesis that, in contrast to the findings of the Endocrine Society, determined that regardless of dose or study duration, the benefits and harms of vitamin D supplements in this population are either nonexistent or trivial, resulting in no net benefit.

Systematic reviews can be complex to dissect (the USPSTF’s synthesis is more than 200 pages long), but after reviewing the evidence closely, I think the Endocrine Society and USPSTF guidelines conflict, because they had slightly different study selection criteria and sliced the data in different ways. The USPSTF, for example, excluded studies of adults living in nursing homes because the focus of its guideline is primary care physicians working in offices and the patients they are most likely to see there. That decision may have obscured benefits of vitamin D in persons with dementia or cognitive impairment, frailty, and/or a history of osteoporotic fractures.

So, what will I say to my next patient without obvious symptoms of a vitamin D-mediated disease who asks if it’s a good idea to take a supplement? Three words: “Save your money.” In general, I trust guidelines written by and for primary care clinicians more than those authored by subspecialists. I also do my best to adhere to the maxim to “do no harm,” even if the harm is a small portion of an older person’s monthly budget that could otherwise be allocated to life’s essentials or an activity that is more likely to improve health.

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