Vitamin D is a fat-soluble vitamin that promotes calcium absorption in the body. Without sufficient vitamin D, bones can become thin, brittle, or misshapen and together with calcium, vitamin D also helps protect older adults from osteoporosis.1
Where is Vitamin D found?
Few foods contain vitamin D including cod liver oil, fatty fish such as salmon, mackerel, tuna, sardines and herring, vitamin D-fortified milk and cereal, and egg yolks are among the best sources.1 Many people may also meet some of their vitamin D needs from exposure to sunlight.2 Dietary supplements are also a source of vitamin D, although you should discuss your daily allowance with your doctor.
Interaction with Warfarin?
Concern has been raised about a possible interaction between vitamin D and warfarin, but the potential for increased activity of warfarin due to vitamin D has not been confirmed by any substantial research.3 Normal amounts of vitamin D should not affect INR test results.
As always, discuss all diet and supplements with your doctor.
- Institute of Medicine, Food and Nutrition Board. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: National Academy Press, 2010.
- Cranney C, Horsely T, O'Donnell S, Weiler H, Ooi D, Atkinson S, et al. Effectiveness and safety of vitamin D. Evidence Report/Technology Assessment No. 158 prepared by the University of Ottawa Evidence-based Practice Center under Contract No. 290-02.0021. AHRQ Publication No. 07-E013. Rockville, MD: Agency for Healthcare Research and Quality, 2007.
- Schrogie JJ. Coagulopathy and Fat-Soluble Vitamins. JAMA. 1975;232(1):19.