Cranberries top the antioxidant list

Cranberries are the fruit with the greatest antioxidant properties, according to a number of studies presented this week at the Experimental Biology 2002 meeting and at the 223rd national meeting of the American Chemical Society earlier this month.

Cranberries were among a number of the most popular fruits investigated by scientists in several separate studies, and were shown to be among the best at fighting cancer, inhibiting the growth of common foodborne pathogens and aiding in the prevention of urinary tract infections (UTIs).

One study presented at the meetings looked at 20 different fruit juices and found that cranberry juice had the highest total phenol content. Biochemist Yuegang Zuo from the University of Massachusetts-Dartmouth said that cranberry juice had "the highest radical scavenging capacity among the different fruits studied."​

In a second study, Catherine Neto, assistant professor at the University of Massachusetts-Dartmouth, isolated several bioactive compounds from whole cranberries and found that flavonoids showed strong antioxidant activity. She also found that newly discovered compounds in the berries were toxic to a variety of cancer tumour cells. "The tumour cell lines that these compounds inhibited most in our assays included lung, cervical, prostate, breast and leukemia,"​ she said.

As well as the cancer fighting properties of the red berries, delegates at the two meetings also heard about the fruit's ability to act as a natural probiotic - supporting the natural bacteria which grow in the human gastro-intestinal tract and killing off the bacteria which promote infections and foodborne illnesses.

A study by Leslie Plhak from the University of Wisconsin-Madison found that whole frozen cranberries contained compounds that inhibited the growth of common foodborne pathogens, including Listeria monocytogenes​ and E. coli 0157:H7​, but enhanced the growth of a beneficial bacterium Lactobacillus fermentum​ by as much as 25 times.

Another study presented at the Experimental Biology conference supported earlier evidence that cranberries contain compounds called proanthocyanidins that may help prevent urinary tract infections (UTIs). Amy Howell, research scientist at the Marucci Center for Blueberry Cranberry Research at Rutgers University and Jess Reed, professor of nutrition at the University of Wisconsin-Madison, have for the first time begun to explain why cranberry may provide this health benefit.

They discovered that an eight-ounce serving of cranberry juice cocktail - but not the equivalent single servings of grape juice, apple juice, green tea or chocolate - prevented E. coli (the bacteria responsible for the majority of UTIs) from adhering to bladder cells in the urine of six volunteers. (UTIs occur when bacteria in the urine bind to cells of the urinary tract wall.)

In addition, they analysed the chemical composition of the proanthocyanidins in these foods, and according to Howell, discovered that "the cranberry's proanthocyanidins are structurally different than the proanthocyanidins found in the other plant foods tested, which may explain why cranberry has unique bacterial antiadhesion activity and helps to maintain urinary tract health"​.