Low-carbohydrate, high-protein diets are a popular weight-loss method, despite a lack of convincing evidence they are more effective that other diets. While high-protein diets do not appear to pose major or immediate safety concerns, subtle health effects may occur, such as interactions with medications. Reports have emerged that Coumadin, a widely used anti-coagulant, may interact with high-protein diets. If you are taking Coumadin, consult your doctor before making any radical changes to your diet.
Interaction
Coumadin, which is a brand name of the drug warfarin, is a common anti-coagulant, or blood-thinning, drug. Finding the dose of Coumadin that precisely balances blood clotting against increasing the risk of excess bleeding is a tricky task. Several case studies have been reported in which people taking Coumadin have experienced a decrease in the effectiveness of the drug after starting a high-protein, low-carbohydrate diet, reports the New York University Langone Medical Center.
Effect
The effectiveness of Coumadin is gauged by a measurement known as the international normalized ratio, or INR, which indicates how long blood takes to form clots. In at least three cases, a patient on a stable dose of Coumadin experienced a drop in INR, meaning the Coumadin was less effective, according to an article published in the April 2008 issue of the medical journal "Pharmacotherapy." Increasing the dose of Coumadin by 16 to 30 percent returned the INR to effective levels. Additional research is needed to confirm how widespread this effect is.
Ending the Diet
In all three cases, when the patients ended the high-protein diet, their INR increased again, requiring a reduction in Coumadin in order to maintain the INR at safe levels, according to an article published in the April 2005 issue of the journal "Annals of Pharmacotherapy." If you are taking Coumadin, consult your doctor and receive more frequent INR testing if you are planning to start or stop a high-protein diet.
Mechanism
The exact reason behind the effect of a high-protein diet on Coumadin is unknown. One theory hypothesizes that high-protein diets increase the levels of a liver enzyme known as cytochrome P450. This enzyme plays a major role in breaking down drugs in the liver. An increase in cytochrome P450 could lead to faster metabolism of Coumadin, resulting in decreased activity, according to the article published in "Pharmacotherapy."
References
- New York University Langone Medical Center: Low-Carbohydrate Diet; February 2011
- "Pharmacotherapy"; Potential interaction Between Warfarin and High Dietary Protein Intake; Hornsby et al.; April 2008
- "Annals of Pharmacotherapy"; Decreased Warfarin Effect after Initiation of High-Protein, Low-Carbohydrate Diets; Beatty et al.; April 2005
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