Harvard Health Letter

In Brief: Cranberry juice and warfarin: Okay together?

In Brief

Cranberry juice and warfarin: Okay together?

Of all the juices on the grocery shelves, cranberry juice seems the most medicinal. It's partly that bright-red color and tart taste. But evidence that drinking cranberry juice lives up to its reputation as a way to fend off urinary tract infections (UTIs) has much to do with it. The highly regarded Cochrane Collaboration — experts who conduct in-depth reviews of published studies — gave cranberry juice (and tablets) a thumbs-up after identifying two high-quality randomized clinical trials that showed daily consumption reduced the number of symptomatic UTIs in women. Other results hint of protection against other sorts of infections.

But cranberry juice has drawbacks. Because it's so tart, manufacturers typically mix it with water and some kind of sweetener, usually high-fructose corn syrup or concentrates of extra-sweet juices, like white grape juice. A cup of Tropicana's ruby red grapefruit juice contains 90 calories, a cup of orange juice, 110. The calorie count for a cup of the company's cranberry juice cocktail is about 140 calories, the same as for a 12-ounce can of Coca-Cola.

The other drawback of cranberry juice is its interaction with warfarin (Coumadin), the anticoagulant that's often prescribed to lower people's stroke risk. Some research has suggested that cranberry juice inhibits the CYP2CP enzyme in the liver that breaks down warfarin.

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