The number of US adults taking daily vitamin D supplements of 1000 IU or more and 4000 IU or more increased from 1999 through 2014, which may increase the risk of adverse effects, researchers reported in JAMA.
Mary R. Rooney, MPH, from the Division of Epidemiology and Community Health, University of Minnesota in Minneapolis, and colleagues assessed trends in daily supplemental vitamin D intake of 1000 IU or more and 4000 IU or more between 1999 and 2014 using data from the National Health and Nutrition Examination Survey.
The recommended dietary allowance for vitamin D is 600 IU/d for adults aged 70 years or younger and 800 IU/d for those who are older than 70 years. The tolerable upper limit is 4000 IU/d, with the risk of toxic effects increasing above this level.
A total of 39,243 participants were included in the analysis; the mean age was 46.6 years, 51.1% were women, and 69.7% self-reported as non-Hispanic white.
The prevalence of daily supplemental vitamin D use of 1000 IU or more in 2013-2014 was 18.2%, compared with a rate of 0.3% in 1999-2000. In 2013-2014, the prevalence of daily supplemental intake of 4000 IU or more was 3.2%. Prior to 2005-2006, the prevalence of daily intake of 4000 IU or more was less than 0.1%.
The researchers found trends of increasing supplemental vitamin D use in most age groups, race/ethnicities, and men and women. In 2013-2014, an intake of 4000 IU or more per day was highest among women (4.2%), non-Hispanic white individuals (3.9%), and those who were 70 years or older (6.6%).
Overall, 3% of participants exceeded the tolerable upper limit of 4000 IU daily and may be at risk of adverse effects; 18% exceeded 1000 IU daily, which may be an indicator of intentional use of supplemental vitamin D.
“Although research has emphasized possible benefits of vitamin D, high dosages pose potential risks,” stated the researchers. “A randomized clinical trial with high-dose vitamin D supplementation found increased risk of fractures and falls, and an increased risk of kidney stones has been found with vitamin D taken in combination with calcium. Some epidemiologic investigations have reported adverse associations of high 25(OH)D levels with prostate cancer, pancreatic cancer, and all-cause mortality.”
- Rooney MR, Harnack L, Michos ED, Ogilvie RP, Sempos CT, Lutsey PL. Trends in use of high-dose vitamin D supplements exceeding 1000 or 4000 International Units Daily, 1999-2014. JAMA. 2017;317(23):2448-2450. doi: 10.1001/jama.2017.4392