Many people eat cranberries on Thanksgiving and then tend to forgot about them the other 364 days of the year. But there may be good reason to consume these tart red berries year round—whether fresh, frozen, jellied, dried or in juice.
Cranberries: SOS for UTIs
Much research supports the use of cranberries (especially the juice) to prevent urinary tract infections (UTIs). Results vary and are modest, however. There’s no evidence that cranberry products can treat a UTI.
UTIs are usually caused by E. coli, a common intestinal bacterium. Substances in cranberries called proanthocyanidins may help prevent the bacteria from sticking to the lining of the urinary tract. A 2009 review by the Cochrane Collaboration, which evaluates the scientific literature, found cranberries most effective for women with recurrent infections (women are more prone to these infections than men).
However, a large, well-designed study published in Clinical Infectious Diseases in 2011 found that in healthy, college-age women (those considered at highest risk for UTIs), 16 ounces of daily cranberry juice cocktail—which contains added sugar—offered no more protection than a placebo drink against UTI recurrences. Few studies have looked at cranberries and UTI prevention in older people, but some research suggests there is little benefit for them. (Incidentally, no health claims for the berries are allowed in the U.S., but France and Canada allow labels to state that cranberries help reduce adhesion of bacteria to urinary tract walls.)
Studies have used different amounts of cranberry juice, but a common recommendation is 10 to 16 ounces daily of cranberry juice cocktail. If you buy undiluted, unsweetened juice, you can use much less but it’s very tart. It’s not known how beneficial cranberry supplements are; they are not standardized and have been less studied.
There have been concerns that cranberries—especially concentrated cranberry extracts—may interact with anti-clotting drugs, similar to the way grapefruit juice affects some medications. The package insert of the blood thinner warfarin (Coumadin) warns users not to drink cranberry juice, but several recent studies using amounts up to 21 ounces a day found no problem. And a review in the American Journal of Medicine in May 2010 concluded that moderate amounts of cranberry juice (no more than 2.5 cups of day) do not affect blood thinners.
What lab research on cranberries suggests
For oral health. Cranberry proanthocyanidins inhibit the bacteria involved in cavities and periodontal disease from attaching to surfaces in the mouth—similar to what occurs in the urinary tract. They also inhibit acid production and reduce inflammatory processes in the mouth, among other benefits. Because of added sugar and processing, cranberry juice cocktail is not likely to be protective, but isolated compounds may one day find their way into mouthwashes and toothpastes.
For heart health. Antioxidants in cranberries may improve blood vessel functioning and protect against oxidation of LDL (“bad”) cholesterol. A small study of people with type 2 diabetes, published in Diabetic Medicine in 2008, found that cranberry extracts lowered LDL by about 15 points, on average.