Cranberry is best known to
most as an edible fruit, the stuff of jelly and
juice, rather than a medicinal herb. However,
cranberry juice has evolved, much like Aloe vera,
as a quintessential American folk remedy - so
well-known in the popular mind as a sure-cure for
urinary infections that it prompted scientists to
begin to investigate its value more than seventy
What Are Cranberries?
What are cranberries and where do they come
from? Depending upon where you live or how you
define them, cranberries may come from different
plant species. Here in North America, commercial
cranberries are the fruits of a tiny bog plant,
scarcely a half a foot tall, known to botanists as Vaccinium macrocarpon. The name Vaccinium comes from an ancient Greek word
derived from prehistoric Mediterranean languages,
referring to berry-producing shrubs. In addition to
cranberries, the genus Vaccinium encompasses
blueberries, whortleberries, huckleberries, and
bilberry. "Macrocarpon" means large fruit.
The native American
bog-cranberry (V. macrocarpon) occurs in
much of eastern North America in bogs from
Newfoundland to Manitoba, south to Virginia, Ohio,
and northern Illinois, and locally to the mountains
of North Carolina. The designation "large-fruited"
cranberry distinguishes our cranberry of the
supermarket from the small cranberry V.
oxycoccos, a diminutive plant which occurs
throughout the northerly regions of the northern
hemisphere, notably the north of Europe, but also
in North America in bogs south to New Jersey,
Pennsylvania and Minnesota. It has considerably
smaller fruits, which turn brownish red, and are
not as appealing as our common cranberry.
When European settlers
first arrived from northern Europe, they were quick
to adopt our native V. macrocarpon, with its
larger, sweeter fruits, as the cranberry of choice.
Hence this species now dominates the market,
cultivated on thousands of acres in Massachusetts,
Michigan, British Columbia and elsewhere.
A few other plants claim
the name "cranberry", including Vaccinium
vitis-idaea, known to American botanists as
Lingonberry, or mountain cranberry, but to the
Swedes, it is cranberry. Cramp-bark, as it is most
commonly known in the American market, Viburnum
opulus, is sometimes listed as "highbush
cranberry", but it is a "cranberry" in name
Our subject is the common American cranberry.
Peter Kalm, an eighteenth century Swedish botanist
who conducted extensive botanical explorations of
the North American wilderness, described the plant
in his 23 February 1749 entry in Travels in
cranberry, Vaccinium hispidulum, is extremely
abundant in North America and grows in such places
as we commonly find our cranberries in Sweden.
Those in America are probably bigger, but in
qualities so like the Swedish that many people
would take them to be just another variety. The
English call them cranberries, the Swedes tranbär and the French in Canada atopa, (atocas) which is a name they have
borrowed from the Indians. They are brought to
market every Wednesday and Saturday at
Philadelphia, late in autumn. They are boiled and
prepared in the same manner as we do our red lingon, or Vaccinium vitis idaea, and they
are used during winter and part of summer in tarts
and other kinds of pastry. But as they are very
sour, they require a great deal of sugar. That is
not very dear, however, in a country where the
sugar plantations are near by. Quantities of these
berries are sent over, preserved, to Europe and to
the West Indies.
Many early travelers, especially hunters and
trappers, expressed joy at finding a large bog in
the North in the fall months, covered with red
cranberries and teaming with wild rice. They were
known as a refreshing, invigorating food, which
could be dried for winter. Many also reported the
fruits to be valuable for staving-off scurvy
(vitamin C deficiency), and were useful as a
diuretic. One of the most important early
nineteenth century writers on American medicinal
plants, Constantine Samuel Rafinesque, described
medicinal uses for cranberries in 1830.
"The large Cranberries
peculiar to America, are the most usually gathered
for our markets, and are even exported to Europe
and the West Indies: keeping pretty well in
barrels, and still better in bottles . . . They are
usually as large as cherries, and somewhat similar
in shape and color . . . Properties [are]
refrigerant, laxative, anti-bilious, anti-putrid,
diuretic, sub-astringent, &c. Useful in fevers,
diarrhea, scurvy, dropsy, and many other diseases.
. . Cranberry tarts are one of the American table
luxuries. Their juice mixed with sugar or alcohol
keeps a long while, and forms a fine acidulous
drink with water, allaying thirst, and lessening
the heat of the body."
as a Urinary Antiseptic
The diuretic use of cranberries was first
reported in a 1787 Latin work on American medicinal
plants. A woman with dropsy (water retention) was
reportedly cured of dropsy by eating large
quantities of the berries. This knowledge trickles
down from the eighteenth century literature to
become common information on the brink of the
twenty first century. Scientific evidence as it
relates to the health of the urinary tract was
first recognized by German physicians in the
mid-1800s. They had observed that after ingesting
cranberries, urinary excretion of hippuric acid was
increased. This led to the belief that cranberries
contained a compound, perhaps benzoic acid, that
the body metabolized to produce hippuric acid in
the urine. In high concentrations, hippuric acid
was believed to have strong antibacterial
Taking this theoretical
basis one step further, researchers N. R.
Blatherwick and M. L. Long conducted a small human
study (involving only two individuals) published in
1923. These scientists attempted to study the
ability of cranberries to acidify urine in healthy
individuals. The patients were given the same diet
for several days. Then one person was given 305 g
of cooked cranberries, while the other was given
prunes. The urinary pH of the cranberry subject
decreased (became more acidic), total acid
excretion increased, while concentrations of
urinary hippuric acid increased from 0.77 g to 4.74
Despite these findings, in
the real world, few people ingest over 10 ounces of
cooked cranberries at one sitting. Further studies
in the 1950s and 60s gave less convincing results,
enhancing cranberry controversies. A 1959 study
found that drinking about a gallon of cranberry
juice a day (4 L) failed to produce enough hippuric
acid excretion to cause antibacterial effects at a
pH level of 5. At a somewhat higher pH (5.6) the
effectiveness of hippuric acid as an antibacterial
was found to decrease by 5-fold. A 1967 study,
again, using a small sampling of only 4 to 5
subjects, showed that cranberry juice cocktail
(one-third cranberry juice mixed with water and
sugar, the typical cocktail of commerce), showed
insignificant changes in urinary pH, even after
slugging gallons of cranberry juice cocktail for
four days. While some studies from the 1920s to the
1970s suggested that urinary acidification was the
mechanism by which cranberry juice produced an
antibacterial effect in the bladder, other studies
conflicted with this theory. Still, the belief that
cranberry juice produced urinary antiseptic effects
persisted in the popular mind.
Information - New Hope
Studies in the 1980s began to shed some new
light on other possible mechanisms of action that
could explain antibacterial effects of cranberry
juice, without relating it to urinary acidification
and hippuric acid. In 1984 a paper was published in
the Journal of Urology and a 1988 Microbios paper showed that when fed to
mice, cranberry juice inhibited the adherence of Escherichia coli (the dreaded E. coli of food-gone-bad) to the epithelial cells in mice
urinary tracts by 80 percent. Similar activity was
found in human subjects as well.
Was a chemical in the
juice responsible for the new found E. coli anti-adherence action? The first evidence came in
1989, when an Israeli research group looked at
chemical fractions of a number of fruit juices.
They found that fructose, a common sugar in many
fruit juices, had some anti-adherence effect on the
bacterium. They also found that a nondialyzable
polymeric compound isolated from cranberry juice
(and blueberry juice) had the most potent effect.
The evolving theory now became that this compound
produced an antibacterial effect in the gut or the
bladder by adhering to the tiny hairs of the
bacterial surface, thus preventing them from
implanting in the tissue mucosal linings, and
simply flushing them out of the body via the urine.
In 1991 Israeli researchers, publishing in The
New England Journal of Medicine, duplicated the
previous studies and confirmed the results.
While the new pharmacological theories were
intriguing, the scientific evidence for the
effectiveness of cranberry juice as a urinary
antiseptic was scant at best. Clinical trials were
uncontrolled, involved a small number of patients,
and produced conflicting results. The jury was
A breakthrough in evidence
came in a 1994 study published in the Journal of
the American Medical Association. A team of
researchers associated with Harvard Medical School
and various Boston-area hospitals conducted a
randomized, double-blind, placebo-controlled study
on 153 elderly women volunteers with an average age
of 78 and a half years. This patient group was
considered appropriate for the study since a large
percentage of women over 65 years of age experience
at least one urinary tract infection per
The study lasted for six
months. Volunteers were randomly assigned to
consume either 300 mL of cranberry juice cocktail
per day or a placebo drink, made to look and taste
like cranberry juice, but without cranberry
content. The study was designed to measure whether
cranberry juice has an effect on bacteriuria (the
passage of bacteria in the urine) or pyuria
(presence of pus, indicating white blood cells,
hence infection in the urine).
The researchers measured
baseline urine samples and six clean-voided urine
samples collected at one month intervals during the
six month duration of the study, looking for
bacteria or white blood cells. At the end of the
study, the researchers concluded the cranberry
juice beverage did indeed reduce the frequency of
both bacteriuria and pyuria in elderly women. This
study provided the first good clinical evidence in
a relatively large sampling of patients, that
cranberry juice could be beneficial to the urinary
A recent study suggested
that drinking 4 to 6 ounces of cranberry juice
daily had a preventative effect for urinary tract
infections rather than a curative effect. The study
was conducted in elderly patients in nursing homes.
Patients were given small amounts of cranberry
juice each day for seven weeks. Of the 28 patients
monitored, urinary tract infections were prevented
in nineteen subjects. The remaining nine patients
had significant colony counts of Gram negative
bacteria, despite drinking cranberry juice. An
additional small study that looked at the use of a
cranberry juice concentrate in 800 mg capsules in
21 patients taking 12 capsules a day, found that
six of those patients with pre-existing urinary
tract infections had no results from the capsules.
This led to the conclusion, once again, that
cranberry juice cocktail or cranberry concentrates
in capsules or tablets may have a better
preventative effect for elderly populations, rather
than a curative effect. More research is
Adding to cranberry's
potential health benefits, a recent study found
that an extract of cranberry inhibited an enzyme
associated with a reduction in cancer risk.
to Use Cranberry
Health conscious consumers have come to believe
capsulated or tableted cranberry extract products
have a distinct advantage over cranberry juice
cocktail in that the high levels of added sugar
added to cranberry juice are absent from the
extracts. Cranberry juice cocktail is a 33%
dilution of pure juice with added sugars for
flavoring. The extract is available in dietary
supplement products as fruit or juice concentrates
concentrate in 800 mg capsules. For those who
prefer a refreshing beverage, in various studies
between 5 to 20 ounces of cranberry juice cocktail
daily is considered effective as a preventative for
urinary infections. Six ounces of juice is equal to
90 g (about three ounces) of fresh fruit.
No doubt cranberry juice,
its extracts and concentrates will continue to
attract interest from consumers and scientists
alike. Now that it's mechanism of action is better
understood, new clinical studies will likely focus
on the optimum products and dosage regimes. Now
that we can reasonably assume that cranberry works,
the question becomes, how does it work best?
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Bacteriuria and Pyuria After Ingestion of
Cranberry Juice. Journal of the American
Medicinal Association, 1994
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al. Studies of Urinary Acidity II: The Increased
Acidity Produced by Eating Prunes and
Cranberries. Journal of Biological
Chemistry, 1923, 57:815.
- Bodel, P. T., et al.
Cranberry Juice and the Antibacterial Action of
Hippuric Acid. Journal of Laboratory and
Clinical Medicine, 1959, 54:881.
- Bomser, J., et al. "In
vitro Anticancer Activity of Fruit Extracts from Vaccinium Species."Planta Medica 1996, 62(3): 212-216.
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for Your Health. Loveland, Colorado:
Interweave Press, 1996.
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Effects of Cranberry Juice on Urine. Journal
of the American Dietetic Association, 1967,
- Kalm, P. Travels in
North America, 2 vols., (reprint of 1770
English edition), New York, Dover Publications,
- Ofek, I., et al.
Anti-Escherichia Coli Adhesion Activity of
Cranberry and Blueberry Juices. New
England Journal of Medicine 1991,
- Rafinesque, C.S. Medical Flora : or Manual of the
Medical Botany of the United States of North
America, Vol. 2. Philadelphia: Samuel C.
- Schmidt, D. R. and A.
E. Sobota. An Examination of the Anti-Adherence
Activity of Cranberry Juice on Urinary and
Nonurinary Bacterial Isolates. Microbios 1988, 55:173-181.
- Sobota, A. E.
Inhibition of Bacterial Adherence by Cranberry
Juice: Potential Use for the Treatment of
Urinary Tract Infections. Journal of
Urology, 1984, 131:1013-1016.
- Zafriri, D., et as.
Inhibitory Activity of Cranberry Juice on
Adherence of Type 1 and P fimbricated
Escherichia Coli to eukaryotic cells. Antimicrobial Agents Chemotherapy 1989,