9 JUN 2005
Fights
Virus?
Cranberry juice has long been a prime natural-food weapon against urinary
tract infections in women, and studies show that the good juice deters
infection by preventing disease-causing bacteria from entering body cells.
One study found that when cranberry juice was present, 80 percent fewer
bacteria stuck to cells. Adhering to a host cell is the first step in
a successful infection.
Could cranberry juice also protect cells from viruses?
Apparently so, according to research just reported by Patrice Cohen and Steven Lipson of St. Francis College (Brooklyn, N.Y.). When the researchers bathed animal cells in the red juice (we'll call it juice, but it's actually cranberry juice cocktail, straight from the supermarket!), virtually none of the cells got infected by reoviruses or rotaviruses, two common causes of diarrhea. (The researchers used red blood cells and kidney cells, which are common tests for viral infectivity.) Undiluted juice reduced infectivity by more than 99.9999 percent. When cells were bathed in diluted juice, the protection waned. Juice diluted by 512 parts of water offered no protection.
Cranberry harvesting in Wisconsin Rapids, Wis.,
the nation's leading grower. The cranberry industry helped fund a study
of viral infection. Photo by Jeff Miller
Slug a slug, slug a bug
Adhesion may be even more crucial in viral infection than in bacterial
infection. Viruses must make copies of themselves -- or else they disintegrate
-- but they can't reproduce until they enter a cell and commandeer its
nucleus. And the first step in entering a cell is adhering to the cell
membrane.
But in electron microscope photos, Lipson's research group saw the virus particles floating free of the blood cells. These particles are goners, says Lipson, who was principal investigator of the research project. "If a virus is not attached, it simply degenerates. It needs a living cell to reproduce. Once it's prevented from binding to the host, it would degenerate within hours," or perhaps longer for an especially stable virus.
While some anti-viral medicines, including many used against HIV, go to work only after the virus enters a cell, it's better to prevent entry in the first place.
In other words, the best defense is a good defense, and that's just what happened with the tangy red juice. "The primary result, based on our experiments ... is that the virus particles did not penetrate, and therefore they were just benign," Lipson says. "They were not infectious."
Since the researchers used whole cranberry juice cocktail, they don't know which chemical is causing the protection. (Cranberry juice is about 4 percent of the total ingredients, which also contains a raft of high fructose corn syrup.) It's unlikely that acidity alone is responsible: Red blood cells held at pH 3.5, the acidity of cranberry cocktail, were not protected against infection without the juice.
Red tide: A cranberry harvest in Massachusetts.
Photo: Patricia Walsh US
Census
Caveat slurpur
The lucky finding -- that some viruses cannot penetrate cells in the presence
of cranberry juice -- is only a first step, says Lipson, who plans to
explore the protection from several angles:
Which chemical(s) in the red drink are protecting cells against virus?
As we wait for answers, should we be slurping cranberry juice? For women
with recurring urinary tract infections, it might be a good idea, 
since
other studies make a strong case that the juice deters these painful attacks.
For example, preliminary research reported at the Infectious Diseases
Society of America (September 30, 2004) showed that bacteria had difficulty
adhering to human bladder cells in urine from women who had drunk eight
ounces of cranberry juice.
In women, urinary tract infections start at the opening of the urethra. Bacteria may move to the bladder or even the kidneys. Diagram: NIH
And unlike the average medical miracle, cranberry juice even tastes
good. But one study cannot prove that the juice helps fight viral diarrhea,
Lipson stresses. Although the tests
showed that cranberry juice seems to change host cells into a form that
is resistant to infection, "This was all lab experiments," he warns. "We
did not do any human trials, and I cannot speculate on whether it would
work in human disease."
-- David Tenenbaum
Bibliography
Mechanism(s) of Inactivation by the American Cranberry Vaccinium Macrocarpon
of Mammalian Enteric Viruses, Patrice Cohen et al, American Society for
Microbiology poster presentation, June, 2005.
Cranberry May Offer Protection Against Antibiotic-Resistant Bacteria that Cause UTIs, Amy B. Howell and Betsey Foxman, Journal of the American Medical Association, June 19, 2002.
