Last month I reported on a study’s results regarding trends in vitamin D testing in Medicare patients, where we saw that the number of tests given per 10,000 enrollees jumped from near zero in 2000 to about 1,300 in 2010. In this blog we’re going to look at vitamin D supplement usage in the United States over the same period.
The data come from the National Health and Nutrition Examination Survey (NHANES), which releases new data sets every two years. When analyzed using statistical software that accommodates the data’s “complex survey” design, as done here, the results can be generalized to the non-institutionalized population of the United States.
The continuous version of NHANES (prior to releasing data every two years, there were gaps between surveys) began with data for the years 1999-2000. The most current supplement usage data is for the years 2009-2010. Supplement usage was collected for all participants in every two-year cohort.
Figure 1 summarizes the data. The blue section of each bar represents the percentage of people in that cohort who take no supplements at all. The red section represents those who take at least one supplement, but no supplement containing vitamin D. The green section represents those who get 1 to 999 IUs of vitamin D per day from supplements. The purple section represents those who get 1000 IUs or more a day.
The results are mixed. As you can see, there has been a huge jump in the number of people taking 1000 IUs/day or more. In the first four cohorts, the percentage of the population getting this much vitamin D from supplements was half of 1% or less. In the most recent cohort, this jumped to over 6%.
On the other hand, the number of people taking vitamin D supplements at all, which is 35.3% in the most recent cohort, is actually less than the 36.5% taking vitamin D in 2005-2006. So what we see is that those who have supplemented with vitamin D all along are taking more of it, but those who haven’t used vitamin D supplements in the past still aren’t.
If we look at the results by specific characteristics of the population, older, better educated, and wealthier people are more likely to take vitamin D supplements. Over 50% of those 60 and older now take vitamin D and more than 15% of this group takes more than 1000 IUs/day. Over 50% of college graduates took vitamin D in the two cohorts from 2003 to 2006, but they have dropped back down to 47.5% in the most recent cohort. In the highest income group, over 9% take 1000 IUs/day or more.
Pregnant women constitute the most likely group to take a vitamin D supplement, but in the most recent cohort the number dropped to 59.2% from over 69% in most of the earlier cohorts.
We still have a lot of work to do.