Cranberries: wasted on turkey?

The health benefits of cranberry juice have occupied scientists for some time. This week researchers in the US claim that cranberry juice could prove to be the next weapon in fighting bacteria, especially those which have become resistant to antibiotics.

Researchers from Rutgers University in New Jersey and the University of Michigan discovered that regular consumption of cranberry juice cocktail may offer protection against certain antibiotic resistant bacteria that cause urinary tract infections (UTIs). Their findings were published in a research letter to the editor in the 19 June 2002 issue of the Journal of the American Medical Association​ (JAMA).

The scientists tested the effectiveness of cranberry juice cocktail in disabling a number of Escherichia coli​ (E. coli) bacteria, some of which are resistant to certain drugs. Preventing UTIs could potentially reduce the use of antibiotics, and subsequently reduce further development of antibiotic resistance.

"We found that when subjects consumed cranberry juice cocktail, their urine was capable of preventing not only susceptible, but antibiotic-resistant bacteria from attaching to the urinary tract,"​ said Amy B. Howell, research scientist at Rutgers and lead investigator of the study. "Cranberry acts to promote flushing of these problematic bacteria from the bladder into the urine stream, which should result in a lower rate of infection."​

Betsy Foxman, Professor of Epidemiology and director at the Center for Molecular and Clinical Epidemiology at the University of Michigan School of Public Health and co-author of the study, added: "In light of the increasing antibiotic resistance of many bacteria, the public health significance of the role of foods, such as cranberry juice cocktail, in preventing infections warrants further consideration. A lower number of infections means reduced use of antibiotics and lower potential risk of developing further bacterial antibiotic resistance."​

Howell and Foxman examined various E. coli isolates from the urine of women and men with UTIs, introducing them into urine samples collected from healthy subjects before and after drinking eight ounces of cranberry juice cocktail. The samples taken after the cranberry juice cocktail was consumed prevented 79 per cent of antibiotic resistant bacteria from sticking to the urinary tract cells, while urine samples taken before the cranberry juice cocktail was consumed failed to prevent adhesion. In total, the cranberry juice cocktail prevented 80 per cent of all bacteria tested from sticking, the researchers said.

This study, which was partially funded by Ocean Spray, is also the first to look at duration of the effect of cranberry in the urinary tract, according to Howell. "This research found that cranberry juice cocktail's beneficial effect may start within two hours and can last for up to 10 hours in the urine, which suggests that consuming a serving in the morning and one in the evening may provide more effective anti-adhesion protection than consuming one serving a day."​

A common misconception is that cranberries help maintain urinary tract health by acidifying the urine, but this research supports the suggestion that it is the anti-adhesion properties of the cranberry which are the key to its urinary tract health benefit. Scientists believe that the proanthocyanidins, or condensed tannins, in cranberries prevent certain E. coli bacteria from sticking to the urinary tract and causing infection.

The National Center of Complementary and Alternative Medicine, a branch of the National Institutes of Health, recently approved funding to support further research on the role of cranberry, with one area of emphasis being the effect of cranberry in prevention of UTI, and as an alternative to antibiotics in the treatment of UTI.

Funding for antimicrobial resistance research has increased more than 75 per cent in the US from $7.8 million in 1992 to approximately $13.8 million in 1998, indicating that national concern over resistant bacteria has increased dramatically.