One common question we receive is “How much vitamin D should I be taking…”
And to answer that question honestly, we really don’t know the exact dose of Vitamin D required by each individual since absorption and storage of Vitamin D can differ (as well as how much vitamin D is produced from daily sun exposure – which is an entire post all together).
The current recommendations for vitamin D supplementation in the U.S. are based on the RDA (Recommended Daily Allowances)
Two studies that I use to justify my recommendations to patients for taking at least 2000 IU per day of vitamin D on most days.
The first study looked at researchers in Antartica during the winter when there is essential no or minimal sunlight. This 2009 study looked at the difference in the researchers’ vitamin D levels over 5 months (March through August of 2007) and found that the group that supplemented with 2000 IU/day were able to increase their average serum vitamin D (25-OH) levels from 45 nmol/L to 71 nmol/L while the 1000 IU/daily of vitamin D group only increased their serum vitamin D levels form 44 nmol/L to 63 nmol/L and the 400 IU/day group had a measurable increase of vitamin D (25-OH) levels from 44 to 57 nmol/L.
The second study I use to justify a higher vitamin D supplementation is a 2008 study that looked at Long Island residents (mixed population of Causasians and African-American) that received vitamin D supplementation with close monitoring and adjustment of their vitamin D supplement dosage to try to raise and maintain their blood serum vitamin D (25-OH) levels above 75 nmol/L. This study found that the patients with lighter pigmented skin required on average, about 3000 IU/day of vitamin D and African-American patients required a higher dose of almost 4000 IU/day to reach the target goal of a serum vitamin D (25-OH) level of 75 nmol/L without anyy reported cases of hypercalcemia among the test subjects.
So based on these two studies as well as personal experience with my patients, I typically recommend that they start at a 2000 IU/day vitamin D supplement and then follow their serum vitamin D (25-OH) levels every two to three months until they reach 50 nmol/L or higher of serum vitamin D (25-OH).