Vitamin D supplements are better absorbed when taken with the largest meal of the day, according to a recent study published in the April 2010 issue of Journal of Bone and Mineral Research.
Researchers in the Department of Endocrinology, Diabetes, and Metabolism at the Cleveland Clinic Foundation noticed that patients with vitamin D deficiency were not achieving increased blood levels of the vitamin, despite receiving large, daily doses of either vitamin D2 or D3. Daily doses ranged from 1,000 to 50,000 IU daily.
Since vitamin D is a fat-soluble, the researchers hypothesized that absorption rates would improve if patients supplemented with the largest meal of the day. Patients typically supplemented on an empty stomach, with a small breakfast or lunch.
To test their hypothesis, researchers studied 17 adults who were not responding to treatment for vitamin D deficiency. Thirteen of the participants were female and 4 were male, with ages ranging from 53 to 75 years old. All had a variety of pre-existing health conditions.
Study participants were divided into three subgroups, depending on weekly vitamin D dosing levels: <50,000 IU; 50,000 IU and >50,000 IU. Those receiving 50,000 IU or more per week received an oil-based preparation of vitamin D2. Those receiving less than 50,000 IU per week received either an oil-based or solid preparation of vitamin D3.
Subjects were instructed to dose with their largest meal of the day, typically dinner, but the daily dosing levels remained unchanged. Since each subject was supplementing on an out-patient basis, it was not possible to determine fat, carbohydrate and protein content for each meal. For this reason, meal size was the focus of the study.
Total vitamin D level was analyzed after 2 to 3 months and the results were positive. Blood levels of vitamin D increased by an average of 50%. Results were not affected by vitamin D preparation (oil or solid) and toxicity did not appear to be an issue for participants.
The Bottom Line
As this study points out, taking vitamin D supplements with food improves absorption. It also demonstrates that short-term supplementation of this fat-soluble vitamin well beyond the RDA is safe and non-toxic.
This news is timely as substantial published studies justify a reevaluation of the RDA in healthy populations. Researchers recommend increasing the RDA for adults from 400 to 800 IU and increasing the Upper Intake Level from 2,000 to 10,000 IU. Medical organizations like the American Academy of Pediatrics also recommend increasing the RDA in children from 200 to 400 IU.
To address this issue, the Food and Nutrition Board (FNB) established an expert committee to review the Dietary Reference Intakes (DRIs) for vitamin D (and calcium). The current DRIs for this nutrient were established in 1997. The FNB is expected to issue its report in September 2010.
Based on the scientific evidence, VitaMedica’s Multi-Vitamin & Mineral Program was reformulated in May 2010, with the amount of vitamin D3 increasing from 375 to 900 IU.