Beneficial Effects Of Cranberry Juice On Urinary Tract

Urinary tract infections affect more than 10 million people in the United States each year. Women have a 1-in-5 chance of getting such an infection in their adult lifetimes. Those who do have an initial infection have a much higher risk of reoccurring urinary tract infections. Cranberries contain compounds that reduce the risk of urinary tract infections. Evidence supporting cranberry benefits comes from well designed, placebo-controlled, human studies.

Blocking Bacterial Stickiness

Cranberry proanthocyanidins block bacterial adhesion to urinary tract cells, according to Dr. Amy Howell, associate research scientist at the Marucci Center for Blueberry and Cranberry Research at Rutgers University. Foods such as dark chocolate and green tea also contain proanthocyanidins, but of a different chemical structure. These may have heart and cancer benefits, but will not help maintain a healthy urinary tract.

Fewer Bacterial Infections

In 1994 a clinical trial shifted cranberry's claims from folklore to science. It was published in the March issue of the "Journal of the American Medical Association" by Dr. Jerry Avorn. For 122 women, during a period of six months, the half who drank 300 ml/day of cranberry juice cocktail had 58% fewer bacteria-positive urine samples. A 2007 review by Dr. Ruth Jepson in the June issue of "Molecular Nutrition and Food Research" summarized Avorn's work and eight other cranberry clinical trials, She concluded that the risk of urinary tract infections was reduced in otherwise healthy people, but did not appear to be of benefit in people with urinary catheters in place because of spinal cord injuries.

Fewer Symptoms

A person's urine can be bacteria positive without any symptoms, but these infections are often accompanied by pain, pain during urination, and the feeling of needing to urinate frequently. According to Dr. Marion McMurdo, as published in the May 2005 issue of "Age and Aging," the 134 men and women who drank 300 ml/day of cranberry juice cocktail for 40 days had 50 percent fewer symptomatic urinary tract infections than the 127 who did not.

Prevention Is Not the Same as Treatment

Proof of lowering the risk of developing a urinary tract infection does not carry over to cranberry working to treat an existing infection. Once a person has a diagnosed urinary tract infection the only evidence-based treatment uses a prescription antibiotic. This has made it difficult to conduct a scientifically sound study. So although it may seem to make sense that drinking cranberry juice could shorten the duration of a urinary tract infection or lessen severity of symptoms, these benefits have not been proven.

Only Cranberry Juice?

What we buy from supermarket shelves is only about 27% cranberry juice. The rest is either water plus sweetener, or other fruit juices. Legally and on the label the description such drinks is "cranberry juice cocktail." One clinical trial, as reported by Dr. Lynn Stothers in the June 2002 issue of "The Canadian Journal of Urology" reported a dietary supplement made from cranberries to be as effective as cranberry juice cocktail. Different cranberry dietary supplements are made by different methods, however, and may not have been tested for efficacy.