Wednesday, November 11, 2009

Cranberry Benefits

Cranberries have long been valued for their ability to help prevent and treat urinary tract infections. Now, recent studies suggest that this native American berry may also promote gastrointestinal and oral health, prevent the formation of kidney stones, lower LDL and raise HDL (good) cholesterol, aid in recovery from stroke, and even help prevent cancer.
Fresh cranberries, which contain the highest levels of beneficial nutrients, are at their peak from October through December, just in time to add their festive hue, tart tangy flavor and numerous health protective effects to your holiday meals. When cranberries' short fresh season is past, rely on cranberry juice and dried or frozen cranberries to help make every day throughout the year a holiday from disease. 

Cranberries have been valued for their ability to reduce the risk of urinary tract infections for hundreds of years. In 1994, a placebo-controlled study of 153 elderly women was published in the Journal of the American Medical Association that gave scientific credibility to claims of cranberries effectiveness in preventing urinary tract infection. In this study, the women given cranberry juice had less than half the number of urinary infections as the control group (only 42% as many, to be precise), who received a placebo imitation "cranberry" drink. The daily dose of cranberry juice in this initial study was just 300 milliliters (about one and one-quarter cups). Since then, a number of other studies have also confirmed anecdotal tales of cranberry's ability to both treat and prevent urinary tract infections. In most of these later studies, subjects drank about 16 ounces (2 cups) of cranberry juice daily.

How does cranberry juice help prevent urinary tract infections? It acidifies the urine, contains an antibacterial agent called hippuric acid, and also contains other compounds that reduce the ability of E. coli bacteria to adhere to the walls of the urinary tract. Before an infection can start, a pathogen must first latch on to and then penetrate the mucosal surface of the urinary tract walls, but cranberries prevent such adherence, so the E. coli is washed away in the urine and voided. Since E. coli is pathogen responsible for 80-90% of urinary tract infections, the protection afforded by cranberries is quite significant.

Studies attempting to explain cranberries' protective effects on urinary tract health were presented at the Experimental Biology Conference held in 2002. 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, compared the proanthycyanins (active compounds) in cranberries to those found in grapes, apples, green tea and chocolate. They 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 anti-adhesion activity and helps to maintain urinary tract health."
8-Ounces Better than 4 to Prevent Bladder Infections

Cranberry's protective effects against bladder infections may be dose responsive, with 8-ounces of cranberry juice being twice as effective as 4-ounces, suggests preliminary research presented at the 42nd Annual Meeting of the Infectious Diseases Society of America by Kalpana Gupta from the University of Washington.
Gupta reported the details of a very small trial in which three volunteers were given 27% cranberry juice cocktail. Urine samples, collected before and 4-6 hours after drinking the cranberry juice, were combined with human bladder cells and incubated with Escherichia coli (the most common cause of bladder infections). The number of bacteria able to adhere to the bladder cells (the first step a pathogen must achieve to be able to cause infection) was significantly reduced in the urine of all women who drank the cranberry juice cocktail, and the effect was doubled when the women drank eight ounces of cranberry rather than four ounces.

Cranberry's protective effect is thought to be due to a specific type of tannin, found only in cranberries and blueberries, which interferes with projections on the bacterium, preventing it from sticking to the walls of the bladder and causing infection. However, once the bacteria have established a hold, it's best to seek medical advice. No evidence shows cranberry juice is able to cure an established bladder infection, which can lead to a more serious kidney infection. The researchers plan further studies in a larger group of women to investigate the optimal amount and frequency of cranberry juice consumption.

Cranberry Juice Shows Promise as Alternative to Antibiotics
New research has greatly increased our understanding of how cranberry juice prevents urinary tract and kidney infections.
A series of studies led by Terri Camesano from Worcester Polytechnic Institute, the latest of which were presented September 19, 2006 at the annual meeting of the American Chemical Society in San Francisco, show that compounds in cranberry juice have the capacity to actually change E. coli bacteria-even strains that have become resistant to conventional treatment-in ways that render them unable to initiate an infection. E. coli, a class of microorganisms responsible for a wide variety of human illnesses ranging from urinary tract and kidney infections to gastroenteritis to tooth decay, are changed in several ways by a group of tannins (called proanthocyanidins) found primarily in cranberries. Each one of these changes can prevent the bacteria from adhering to cells in the body, a necessary first step in any infection.
Cranberry proanthocyanidins:
  • Alter E. coli's cell membranes
  • Prevent the bacteria from making contact with cells or attaching to them even if they somehow manage to get close enough
  • Change the shape of E.coli from rods to spheres
  • Disrupt bacterial communication
Alter E. coli Cell Membranes
In research published February 2006 in Biotechnology and Bioengineering, Camesano showed that exposure to cranberry juice causes tiny tendrils (known as fimbriae) on the surface of the type of E. coli bacteria responsible for the most serious types of urinary tract infections to become compressed. Since its fimbriae are what allow the bacteria to bind tightly to the lining of the urinary tract, compressing them greatly reduces E. coli's ability to remain in place long enough to launch an infection.

No comments: