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.
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.
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