From Ergo Log
You're likely to derive most benefit from vitamin D supplements if you take them with your main meal of the day. Endocrinologists at the Cleveland Clinic Foundation drew this conclusion after doing a small study of 17 patients.
Over half of the inhabitants of developed countries have less than optimal levels of vitamin D in their bodies. It's also becoming increasingly clear that their health is compromised as a result. In theory supplements containing vitamin D can help, but many studies show that these hardly raise the vitamin D level at all.
The doctors Guy Mulligan and Angelo Licata published in the Journal of Bone and Mineral Research the results of a study in which they got a diverse group of 17 patients to take a supplement containing ergocaliciferol [vitamin D2] or cholecalciferol [vitamin D3] for 2-3 months. The dose varied, but all patients took their supplements during the main meal of the day. The researchers' reasoning was that this might help the vitamin uptake.
They were right, as the figure below shows.
"Admittedly, there are several limits to our study, including the small sample size, lack of a control group, and an inability to know exactly how the patients took their supplements", the researchers concede. But that doesn't make their results any less worthwhile.
"Despite these limitations, the results are striking and consistent across a rather heterogeneous group of patients (different disease states and different preparations and doses of vitamin D). It therefore seems reasonable to ask patients to take vitamin D supplements with their largest meal because it may be a cost-effective strategy that could very well help patients to achieve optimal serum levels of 25(OH)D."
J Bone Miner Res. 2010 Apr;25(4):928-30.