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Cranberry
Juice—A Cocktail for the Heart by Janet Raloff
Chemist Joe Vinson has a passion
for foods and the potentially beneficial antioxidants they bring
to the dinner table.
Cranberry-juice cocktail contains just
27 percent berry juice but still is the second-most potent source
of antioxidants among popular fruit juices.
Three years ago, for instance, he reported data
showing that molecule for molecule, the antioxidants in chocolate
exceed the potency of vitamin C. Now he finds another powerful
stash of these protective compounds in cranberries and their juice.
Moreover, the University of Scranton scientist reports this week
at the American Chemical Society's spring meeting in New Orleans,
regular consumption of that juice yields cholesterol benefits
in middle-age men and women.
Many plant-based foods, especially the colorful
ones, contain large quantities of polyphenols. As antioxidants,
these compounds quash the damage that natural oxidants can do
in the body. Indeed, a large number of disorders associated with
aging—including cancer, heart disease, diabetes, and several
types of dementia—have been linked to damage caused by a
slow and unremitting onslaught of oxidants.
In his latest study, Vinson and his colleagues
provided 20 men and women 8-ounce servings of cranberry juice
cocktail, which contains 27 percent juice. He offered his recruits
the type available in stores, which is heavily sweetened with
high-fructose corn syrup and supplemented with extra vitamin C,
or a low-calorie alternative that the Scranton scientists concocted
daily from pure juice. Twelve chose the low-cal juice, which was
sweetened solely with a sugar-free compound.
Drinking cranberry juice three times a day over
the course of a month increased all the volunteers' blood concentration
of high-density lipoprotein (HDL) cholesterol—the so-called
good cholesterol—by 10 percent. The juice didn't affect
low-density lipoprotein (LDL) or triglycerides, which are other
fatty substances in the blood. However, epidemiological studies
by others have correlated HDL-cholesterol increases of this magnitude
with about a 40 percent drop in heart-disease risk, Vinson notes.
Cranberries lead the antioxidant pack
In earlier studies, the Scranton team surveyed
the antioxidant potential of several fruits and vegetables. Overall,
fruits surpassed the veggies, "and cranberries had more antioxidants
than any other fruit," Vinson observes. Several of cranberry's
polyphenol antioxidants are procyanidins, the same family of pigments
that make cherries red.
When the chemists investigated pure cranberry
juice, they found its antioxidant punch exceeded by 50 percent
the potency of its next closest juice competitor, grape juice.
However, because cranberries are so tart, their juice has to be
diluted and sweetened to be palatable. Yet even in this cocktail
form, Vinson found, 27 percent cranberry juice still ranked second
only to pure grape juice in its ability to defuse oxidants.
With funding and cranberries supplied by the Cranberry
Institute, he then investigated antioxidants delivered to the
blood by juice.
To evaluate whether it was the cranberry juice
or the sugar and vitamin C in the cocktail that provided any benefit
in the new study, the Scranton chemists offered just an 8-ounce
glass of the sugar water and the vitamin to 10 men and women as
a breakfast drink. Each had fasted the night before.
Over the next 4 hours, the researchers periodically
sampled the volunteers' blood and tested its ability to quash
oxidants. To Vinson's surprise, the blood actually fostered oxidation.
After a bagel and soft drink at lunchtime, the assays continued
and showed that the potentially unhealthy pro-oxidant effect lasted
a total of 7 hours, Vinson told Science News Online.
On another day, he repeated the tests, this time
giving each volunteer an 8-ounce glass of the sugar-sweetened
cranberry juice cocktail. This time, he notes, "we had a
good antioxidant effect for the whole 7 hours, even after that
blast of high-fructose corn syrup [in the soft drink] and bagel
at lunch."
More juice, better protection
In a follow-up trial, Vinson's team put 20 adults,
mostly middle age and all with moderately elevated, unhealthy
total-blood-cholesterol concentrations, on a cranberry-juice regimen.
For the first month, each person drank a daily 8-ounce glass of
either the sugared or surgarfree cranberry-juice cocktail. During
the second month, each recruit drank two glasses daily. During
the last month of the experiment, daily juice intake increased
to three glasses.
Before the trial and at the end of each month,
the scientists ran a series of tests on the blood of each participant.
Those data confirmed that the antioxidant defense of the blood
increased steadily with the increasing juice intake. Compared
with the before-juice measurements, concentrations of oxidation
products in the volunteers' blood was 15 percent lower after the
first month of the trial and about 40 percent lower by the close
of the third month.
Assays of the participants' blood showed no change
in their triglycerides or total cholesterol concentrations. However,
HDL cholesterol increased—but only in the three-glass-per-day
phase of the trial. Just that's worth a lot, says Vinson. Doctors
lament the fact that although low-HDL cholesterol is a major risk
factor for heart disease, there are few prescriptions they can
offer patients that raise this lipid—other than to give
up smoking, drink a little alcohol, or exercise regularly.
For people who would prefer a pocket version of
the potential cranberry therapy for cholesterol, Vinson notes
that dried berries are available in stores. His assays, by the
way, indicate that dried cranberries pack 10 percent more antioxidants
than prunes and 50 percent more than raisins do.
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Cranberry
for Prevention of Urinary Tract Infections by Darren M. Lynch
Traditionally, cranberry has been used for the treatment and prophylaxis
of urinary tract infections. Research suggests that its mechanism
of action is preventing bacterial adherence to host cell surface
membranes. Systematic reviews have concluded that no reliable
evidence supports the use of cranberry in the treatment or prophylaxis
of urinary tract infections; however, more recent, randomized
controlled trials demonstrate evidence of cranberry's utility
in urinary tract infection prophylaxis. Supporting studies in
humans are lacking for other clinical uses of cranberry. Cranberry
is a safe, well-tolerated herbal supplement that does not have
significant drug inter-actions.
(American cranberry Vaccinium macrocarpon) is
one of only three of fruit native to North America. The other
species are Vaccinium angustifolia) and bilberry (Vaccinium myrtillus).
Cranberry typically grows in bogs and is a member of the same
family as blueberry and bilberry. Massachusetts and Wisconsin
are the main areas of present-day commercial production of cranberry.
The ripe fruit was used medicinally by Native Americans for
the treatment of bladder and kidney ailments. Pilgrims called
the fruit "craneberry" because the stem and flower resembled
the head, neck, and beak of a crane. Therapeutic applications
of cranberries documented during the 17th century included the
relief of blood disorders, stomach ailments, liver problems, vomiting,
appetite loss, scurvy, and cancer. Before the advent of antibiotics,
cranberry continued to be a popular treatment for urinary tract
infections (UTIs).
Pharmacology
The mechanism of action of cranberry has prompted
much scientific discussion. It was first hypothesized that acidification
of the urine contributed to an antibacterial effect. The current
proposed mechanism of action focuses primarily on cranberry's
ability to prevent bacterial binding to host cell surface membranes.
In vitro studies have observed potent inhibition of bacterial
adherence of Escherichia coli and other gram-negative uropathogens.
Cranberry has been found to specifically inhibit hemagglutination
of E. coli by expression of types 1 and P adhesin through
the component compounds fructose and proanthocyanidins.
Uses and Efficacy
URINARY TRACT INFECTION
In the United States, one of every five women
has been reported to have a lifetime incidence of UTI. Of these
women, 3 percent experience recurrent disease. Eleven million
women receive medication for UTIs annually. A recent Cochrane
Database systematic review found no randomized trials assessing
the effectiveness of cranberry juice in the treatment of UTIs
and concluded that there is no evidence to support its use. There
is much greater evidence-based information available for the use
of cranberry in UTI prophylaxis.
The first relatively large placebo-controlled
studies assessing efficacy were conducted in elderly women living
in long-term care facilities. The findings of these studies showed
that cranberry significantly reduced the frequency of bacteriuria
and pyuria, but these were not intention-to-treat analyses. A
1997 study, published as a letter in The Journal of Family Practice,
used a younger cohort of women and was the first study to use
cranberry extract tablets rather than juice. Results showed that
the cranberry concentrate was more effective than placebo in reducing
the occurrence of UTIs. However, only 10 women completed the study.
Another pair of studies found cranberry ineffective in decreasing
bacteriuria in children with neurogenic bladder requiring intermittent
catheterization. A Cochrane Database systematic review, citing
small sample sizes and the poor quality of available trials, determined
that there was no reliable evidence of effectiveness of cranberry
in UTI prophylaxis.
However, since 2001, two good-quality studies
have been published. The first trial of 150 women consisted of
three arms: cranberry/lingonberry juice; probiotic-supplementation
with Lactobacillus GG drink; and no intervention for 12 months.
Findings were a statistically significant 20 percent reduction
in absolute risk of infection in women receiving cranberry compared
with no effect in the probiotic-supplementation and no-intervention
groups. ) Most recently, a randomized, placebo-controlled trial
of 150 women over a 12-month period found that cranberry juice
and cranberry extract tablets significantly decreased the number
of patients having at least one symptomatic UTI per year.
OTHER USES
A single experimental study showed that the "high-molecular-weight
constituent" of cranberry juice that inhibits the adherence
of E. coli was effective in reversing and inhibiting the coaggregation
of a large portion of dental plaque bacteria. Cranberry also has
been recommended as an adjunctive treatment for Candida infections.
In vitro stud-have shown that cranberry juice exerts fungistatic
effects against dermatophytic and other fungi but has no effect
against Candida albicans. There are no controlled trials in humans
evaluating the effectiveness of cranberry in treating fungal infections.
