Cranberries and infections - EFR 5-47

Cranberries are big around this time of year. The following might be an added incentive to adding this fruit on a year around basis.

(Submitted by Mary Cheatham, Extension graduate assistant)

Many people used to, and some still do, advocate drinking cranberry juice to increase the acidity (lower the pH) of the urine and prevent urinary tract infections. Studies have been contradictory about the acidification of urine by drinking cranberry juice. Some studies have not shown acidification of urine even with amounts of 2000 milliliters per day of cranberry juice (that's more than 2 quarts per day!).

Research has shown a possible new mechanism of action for cranberry juice to reduce urinary tract infections. Data has shown cranberry juice can inhibit the bacterial adherence to mucosal surfaces and thus decrease the incidence of urinary tract infections.

A study was done to test the effects of cranberry juice in older women. This population was chosen because they have been found to have a lot of bacteriuria (bacteria in the urine). Bacteriuria was defined as organisms numbering more than or equal to 1 million per milliliter. This study was done in Boston Massachusetts by Brigham and Women's Hospital, Harvard Medical School and the Hebrew Rehabilitation Center for Aged.

One hundred fifty three women of an average age of 78.5 years were randomly divided into two groups. One group consumed the cranberry juice beverage and the other group consumed a cranberry flavored placebo drink. Each person was to consume 300 ml (about 10 oz.) per day of the cranberry beverage. This was a double- blind study with neither the patient nor the people distributing the beverage or collecting urine samples knowing who was getting the real cranberry juice.

A smaller percentage of urine samples had bacteria in the cranberry juice beverage group than the group drinking the placebo. Bacteriuria in the cranberry juice group was only 42% as likely to occur as in the placebo group.

One possible confounding factor in this study was that the group drinking the cranberry juice beverage had a lower previous history of urinary tract infections. This was factored out in the statistical analysis and addressed in the paper.

Source
Reduction of Bacteriuria and Pyuria After Ingestion of Cranberry Juice, Avorn,J., Monane,M., Gurwitz,J.H., Glynn,R.J., Choodnovskiy, I., and Lipsitz,L.A., Journal of the American Medical Association, March 9, 1994 - Vol 271, No. 10, 751-754.