New Vitamin D Recs: Testing, Supplementing, Dosing

This transcript has been edited for clarity. 

I'm Dr Neil Skolnik, and today I'm going to talk about the Endocrine Society Guideline on Vitamin D. The question of who and when to test for vitamin D, and when to prescribe vitamin D, comes up frequently. There have been a lot of studies, and many people I know have opinions about this, but I haven't seen a lot of clear, evidence-based guidance. This much-needed guideline provides guidance, though I'm not sure that everyone is going to be happy with the recommendations. That said, the Society did conduct a comprehensive assessment and systematic review of the evidence that was impressive and well done. For our discussion today, I will focus on the recommendations for nonpregnant adults. 

The assumption for all of the recommendations is that these are for individuals who are already getting the Institute of Medicine's recommended amount of vitamin D, which is 600 IU daily for those 50-70 years of age and 800 IU daily for those above 80 years. 

For adults aged 18-74 years, who do not have prediabetes, the guidelines suggest against routinely testing for vitamin D deficiency and recommend against routine supplementation. For the older part of this cohort, adults aged 50-74 years, there is abundant randomized trial evidence showing little to no significant differences with vitamin D supplementation on outcomes of fracture, cancer, cardiovascular disease, kidney stones, or mortality. While supplementation is safe, there does not appear to be any benefit to routine supplementation or testing. It is important to note that the trials were done in populations that were meeting the daily recommended intake of vitamin D and who did not have low vitamin D levels at baseline, so individuals who may not be meeting the recommended daily intake though their diet or through sun exposure may consider vitamin D supplementation. 

For adults with prediabetes, vitamin D supplementation is recommended to reduce the risk for progression from prediabetes to diabetes. This is about 1 in 3 adults in the United States. A number of trials have looked at vitamin D supplementation for adults with prediabetes in addition to lifestyle modification (diet and exercise). Vitamin D decreases the risk for progression from prediabetes to diabetes by approximately 10%-15%. The effect may be greater in those who are over age 60 and who have lower initial vitamin D levels. 

Vitamin D in older adults (aged 75 or older) has a separate recommendation. In this age group, low vitamin D levels are common, with up to 20% of older adults having low vitamin D levels. The guidelines suggest against testing vitamin D in adults aged 75 or over and recommend empiric vitamin D supplementation for all adults aged 75 or older. While observational studies have shown a relationship between low vitamin D levels in this age group and adverse outcomes, including falls, fractures, and respiratory infections, evidence from randomized placebo-controlled trials of vitamin D supplementation have been inconsistent in regard to benefit. That said, a meta-analysis has shown that vitamin D supplementation lowers mortality compared with placebo, with a relative risk of 0.96 (confidence interval, 0.93-1.00). There was no difference in effect according to setting (community vs nursing home), vitamin D dosage, or baseline vitamin D level. 

There appeared to be a benefit of low-dose vitamin D supplementation on fall risk, with possibly greater fall risk when high-dose supplementation was used. No significant effect on fracture rate was seen with vitamin D supplementation alone, although there was a decrease in fractures when vitamin D was combined with calcium. In these studies, the median dose of calcium was 1000 mg per day. 

Based on the probability of a "slight decrease in all-cause mortality" and its safety, as well as possible benefit to decrease falls, the recommendation is for supplementation for all adults aged 75 or older. Since there was not a consistent difference by vitamin D level, testing is not necessary. 

Let's now discuss dosage. The guidelines recommend daily lower-dose vitamin D over nondaily higher-dose vitamin D. Unfortunately, the guideline does not specify a specific dose of vitamin D. The supplementation dose used in trials of adults aged 75 or older ranged from 400 to 3333 IU daily, with an average dose of 900 IU daily, so it seems to me that a dose of 1000-2000 IU daily is a reasonable choice for older adults. In the prediabetes trials, a higher average dose was used, with a mean of 3500 IU daily, so a higher dose might make sense in this group. 

I know that this is an area where a lot of clinicians have a lot of experience and opinions. I'm interested in yours, how you approach this, and what you think is correct. Please leave your thoughts in the comments section. 

I'm Dr Neil Skolnik, and this is Medscape.