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Cranberry and Urinary Tract Infection • CID 2004:38 (15 May) • 1413
REVIEW ARTICLE
Cranberry Juice and Urinary Tract Infection
R. Raz,
1,2
B. Chazan,
1
and M. Dan
3
1
Infectious Diseases Unit, Haemek Medical Center, Afula,
2
Rappaport School of Medicine, Technion, Haifa, and
3
Infectious Diseases Unit,
Wolfson Medical Center, Holon, Israel
Cranberries have long been the focus of interest for their beneficial effects in preventing urinary tract infections
(UTIs). Cranberries contain 2 compounds with antiadherence properties that prevent fimbriated Escherichia
coli from adhering to uroepithelial cells in the urinary tract. Approximately 1 dozen clinical trials have been
performed testing the effects of cranberries on the urinary tract. However, these trials suffer from a number
of limitations. Most importantly, the trials have used a wide variety of cranberry products, such as cranberry
juice concentrate, cranberry juice cocktail, and cranberry capsules, and they have used different dosing reg-
imens. Further research is required to clarify unanswered questions regarding the role of cranberries in
protecting against UTI in general and in women with anatomical abnormalities in particular.
In women with recurrent urinary tract infections
(UTIs), long-term antimicrobial prophylaxis is indi-
cated [1]. This method is effective but can cause adverse
reactions and can increase emergence of antimicrobial
resistance [2, 3]. Therefore, the need for alternative
therapies for UTI prophylaxis is evident. Cranberries
are one nonantibiotic alternative.
THE FRUIT
The scientific name for cranberry plant is Vaccinium
macrocarpon [4]. Cranberries, blueberries, and Concord
grapes are the only 3 fruits that are native to the United
States and Canada. Most commercial farms today are
located in northern United States, Massachusetts, and
New Jersey and the Canadian provinces of Quebec and
British Columbia [5]. Commercial harvests occur in
September and October.
Cranberries contain
180% water and 10% carbo-
hydrates [6]. Among other constituents are flavonoids,
anthocyanins, catechin, triterpenoids, organic acids,
Received 4 November 2003; accepted 12 January 2004; electronically published
26 April 2004.
Reprints or correspondence: Dr. Raul Raz, Infectious Diseases Unit, Haemek
Medical Center, Afula, Israel (raz_r@clalit.org.il).
Clinical Infectious Diseases 2004;38:1413–9
2004 by the Infectious Diseases Society of America. All rights reserved.
1058-4838/2004/3810-0015$15.00
and a small amount of ascorbic acid. The major organic
acids are citric, malic, and quinic acids, with small
amounts of benzoic and glucuronic acids [7]. Antho-
cyanin pigments obtained from cranberry pulp are used
for coloring applications [8]. Cranberries can be pro-
cessed into fresh fruit, concentrate, sauce products, and
juice drinks [5]. The single-strength juice is very acidic
(pH,
!2.5) and unpalatable. In 1930, cranberry juice
cocktail, comprising a mixture of cranberry juice,
sweetener, water, and added vitamin C, was introduced.
The leading brand of cocktail contains 33% pure cran-
berry juice. Dried cranberry powder formulated in cap-
sules or tablets is also available.
MECHANISTIC STUDIES:
URINE ACIDIFICATION
Native Americans were the first to use cranberries for
their medicinal properties [5]. Cranberries were used
for a variety of complaints, including blood disorders,
stomach ailments, liver problems, and fever. During the
1880s, German physicians observed that urinary ex-
cretion of hippuric acid increased after ingestion of
cranberries. In 1914, Blatherwick [9] published an ar-
ticle showing that cranberries are rich in benzoic acid,
which is then excreted in urine as hippuric acid. Therein
followed a long period during which the usefulness of
cranberry juice was thought to be based on the urinary
excretion of hippuric acid, which is a bacteriostatic
1414 • CID 2004:38 (15 May) • Raz et al.
agent and has the potential to acidify urine [10]. In 1923,
Blatherwick and Long [11] reported a reduction in urine pH
level (6.4–4.5) with a concomitant increase in excretion of hip-
puric acid (0.77–4.74 g) after subjects ate 350 g of cooked
cranberries [12]. In 1933, Fellers et al. [13] published results
for 6 men who ingested 100–300 g of cranberries daily. They,
too, showed an increase in acidity and excretion of organic
acids (including hippuric acid) in urine. However, these authors
concluded that an ordinary serving of 22–54 g of cranberries
produced only a very slight increase in urine acidity [14].
Kinney and Blount [15] found that certain amounts of cran-
berry juice (450–720 mL daily) lowered urinary pH. Similarly,
Jackson and Hicks [16] showed that 710 mL of cranberry juice
(25% pure juice) lowered the urine pH of 21 elderly men. In
contrast, Nahata et al. [17] reported that the addition of vitamin
C to cranberry cocktail did not change urine pH. Notably, an
early study by Bodel et al. [18] in 1959 found that, in 5 healthy
subjects, 1200–1400 mL of cranberry juice cocktail slightly acid-
ified urine and increased the amount of hippuric acid excreted
in urine to 3–4 g. However, none of the urine samples from
these patients was bacteriostatic against Escherichia coli. In ad-
dition, Bodel et al. [18] demonstrated that hippuric acid was
bacteriostatic at a minimum concentration of 0.02 mmol/L at
pH 5.0, and the antibiotic activity of hippuric acid decreased
∼5-fold as the pH increased to 5.6. Bodel et al. [18] concluded
that cranberry juice could not exert a bacteriostatic effect be-
cause it was not a rich enough source of hippuric acid, coupled
with the fact that it did not lower urine pH sufficiently.
The validity of the conclusions of Bodel et al. [18] was sub-
sequently confirmed by others. Today, it is known that the low
amount of benzoic acid present in the fruit (
!0.1% of weight),
coupled with maximum tolerated amounts of cranberry juice
(∼4 L/d), rarely results in enough hippuric acid excretion nec-
essary to achieve bacteriostatic urinary concentrations [19]. In-
gestion of large amounts of cranberry juice is required to
slightly reduce pH of urine and modestly increase hippuric acid
excretion, changes that do not confer significant antibacterial
activity to urine. If cranberry juice is a protective agent for the
urinary tract, then another mechanism must be involved.
MECHANISTIC STUDIES: ANTIADHERENT
PROPERTIES
Adherence of uropathogens to uroepithelial cells is the initial
step in pathogenesis of UTI [20]. In 1984, Sobota [21] was first
to suggest that “reported benefits derived from the use of cran-
berry juice may be related to its ability to inhibit bacterial
adherence” (p. 1013). Sobota found that cranberry juice cock-
tail reduced adherence by
175% in 160% of 77 clinical isolates
of E. coli recovered from patients with UTI. Fifteen of 22 sub-
jects showed significant antiadherence activity in their urine 1–
3 h after drinking 15 oz (443.6 mL) of cranberry juice cocktail
[22].
Since Sobota’s initial report, several studies have confirmed
that the presumed efficacy of cranberry in preventing UTI is
related to its antiadherent properties. It is now known that E.
coli, the most common cause of UTI, have hairlike fimbria that
protrude from their surface. The fimbriae produce 2 adhesins
(mannose sensitive and mannose resistant) that attach to re-
ceptors on uroepithelial cells [23].
Zafriri et al. [24] identified 2 compounds in cranberries that
inhibit E. coli adhesins. One is fructose, which inhibits the
mannose-sensitive fimbrial adhesins; the other is a high-
molecular-weight compound that inhibits the mannose-resis-
tant adhesins of uropathogenic E. coli [25]. Although all fruit
juices contain fructose, only juices from Vaccinium berries (i.e.,
cranberries and blueberries) contain this second unique pol-
ymeric compound [26], which was later named “proantho-
cyanidin.” Interestingly, proanthocyanidin shows a very strong
inhibitory activity against mannose-resistant adhesins produced
by urinary isolates of E. coli [25] but shows only moderate
antiadherent activity against fecal E. coli isolates [27].
The antiadhesive property of cranberries probably helps to
prevent UTI in 2 ways: first, it directly prevents E. coli from
adhering to uroepithelial cells; and second, it selects for less
adherent bacterial strains in the stool. A recent study showed
that regular consumption of cranberry juice was also effective
in cases in patients with UTI caused by antibiotic-resistant
bacteria [28]. Urine samples obtained from healthy volunteers
who drank cranberry juice prevented uropathogenic E. coli iso-
lates from adhering to isolated uroepithelial cells in bioassays.
The antiadherent effect started within 2 h and persisted for up
to 10 h after ingestion [29].
CLINICAL STUDIES
UTI prophylaxis. The first clinical study evaluating the effect
of cranberry on urinary tract was published in 1966. Papas et
al. [30] described the effect of cranberry juice in 60 patients
with bacteriuria who received 480 mL of juice daily for 3 weeks.
After therapy, 53% had a positive response and an additional
20% had a more modest benefit, but 6 weeks after stopping
treatment, bacteriuria reappeared in most of the subjects.
Since the study of Papas et al. [30], about a dozen clinical
trials evaluating various cranberry products have been per-
formed. All these subsequent trials have studied the effect of
cranberry in preventing urinary tract symptoms. In some of
them, the primary parameter tested was UTI; in other studies,
bacteriuria was the primary end point. These trials have eval-
uated various patient populations, including sexually active
adult women, elderly or pediatric patients, and patients with
Cranberry and Urinary Tract Infection • CID 2004:38 (15 May) • 1415
different medical conditions. Table 1 summarizes the relevant
prospective clinical studies conducted with cranberry products.
Kontiokari et al. [32], Stothers [31], and Walker et al. [35]
published randomized studies that examined adult women. In
the study by Kontiokari et al. [32], which was an open, ran-
domized, controlled trial, 150 women were divided into 3
groups: one group drank 50 mL a day of cranberry-lingonberry
juice concentrate containing 7.5 g cranberry concentrate and
1.7 g lingonberry concentrate (lingonberry is another fruit of
the Vaccinium genus); another group drank 100 mL of a lac-
tobacillus drink; and a third group received no intervention.
After 6 months’ treatment, 16% of the cranberry group, 39%
of the lactobacillus group, and 36% of the control group had
experienced ⭓1 recurrence of UTI. This translates to a 20%
reduction in absolute risk for the cranberry group. Interestingly,
even though the cranberry group stopped their treatment after
6 months (because the manufacturer stopped producing the
juice), the percentage of women who experienced recurrence
at 12 months was still significantly lower in the cranberry group,
implying a residual effect supporting the hypothesis that cran-
berry selects for less adherent bacterial strains.
Stothers [31] performed a randomized, placebo-controlled,
double-blind study. A total of 150 women with previous UTI
were divided into 3 groups: persons who received placebo juice
and placebo tablets, persons who received cranberry juice and
placebo tablets, and persons who received placebo juice and
cranberry tablets. Juice was 250 mL of pure unsweetened cran-
berry juice taken 3 times daily, and tablets contained 1:30 parts
concentrated juice taken twice daily. After 1 year, results showed
that 32% of placebo recipients had experienced ⭓1 UTI during
the year, compared with 20% in the cranberry juice group and
18% in the cranberry tablet group. The absolute risk reduction
for cranberry products was 12%–14%, similar to the findings
of Kontiokari et al. [32].
A smaller study by Walker et al. [35] adds further support
to the above findings. In this study, which followed a double-
blind crossover design, 19 women with recurrent UTI were
provided either cranberry capsule (with 400 mg cranberry sol-
ids) or a placebo capsule for 3 months. Patients then switched
to an alternative therapy for the next 3 months. Although only
10 patients finished the entire course of treatment, results fa-
vored the use of cranberry. Of 21 episodes of UTI, 6 occurred
in the cranberry group and 15 occurred in the placebo group.
Overall, these 3 studies show that use of cranberry is effective,
at least statistically, for prophylaxis of UTI in adult women with
recurrent UTI. It should be noted, however, that none of these
3 studies used the popular commercial brand of cranberry juice
cocktail.
Of interest too is an epidemiological study [40] that evaluated
the relationship between health/sexual behavior and first-time
UTI in sexually active women. The study found that regular
drinking of cranberry juice was associated with decreased risk
of UTI. Although this study was retrospective and examined
first-time UTI and not recurrent UTI, it adds to the notion
that young, sexually active women constitute a population that
may benefit from cranberry products.
Two studies have evaluated the use of cranberries in elderly
women, but unlike the above 3 prospective studies, these trials
chose bacteriuria as their primary parameter. Avorn et al. [38]
conducted a large randomized, double-blind study in which
153 asymptomatic elderly women received 300 mL per day of
cranberry juice cocktail or placebo. Urine samples were ob-
tained at baseline and at 1-month intervals for 6 months, and
tested for bacteriuria and pyuria. At baseline, bacteriuria and
pyuria were present in ∼20% of samples in both the cranberry
group and the placebo group. At the 1-month mark, there was
no difference in the percentage of urine samples with bac-
teriuria and pyuria in the 2 groups (∼25%). However, from
the 2-month mark on, there was a statistically significant dif-
ference between groups favoring the cranberry group. At the
end of the 6-month study, bacteriuria and pyuria were present
in 28% of urine samples from the cranberry group. The chances
of having bacteriuria with pyuria were 42% less in the cranberry
group than in the control group. These authors concluded that
ingesting cranberry beverages reduced the frequency of bac-
teriuria with pyuria in older women, although they noted that,
in elderly women, asymptomatic bacteriuria does not usually
require treatment. Nevertheless, in their study, there were 16
instances of antibiotic use for UTI in the control group versus
8 in the cranberry group.
Haverkorn and Mandigers [39] also evaluated the use of
cranberry by elderly patients, but they used a nonblinded cross-
over design. Men and women in a nursing department of a
general hospital were provided 15 mL cranberry juice (type not
detailed) mixed with water twice daily or the same amount of
water daily. After 4 weeks, the regimens were reversed. Only
17 patients stayed in the department long enough to complete
both 4-week periods. Bacteriuria was observed in 3 patients
during the entire time course and in neither period in 7 patients.
In the additional 7 patients, there were fewer instances of bac-
teriuria during the cranberry period than during the control
period, supporting a moderately preventive role for cranberry
juice.
Two additional but not randomized trials involving elderly
patients were conducted. In a Danish trial [33], the incidence
of UTI was compared in 2 geriatric departments. Patients were
offered cranberry juice in one department and the usual mixed
berry juice in the other. The results showed that cranberry juice
did not influence incidence of UTI. In another study, 538 nurs-
ing home residents were provided either 220 mL of cranberry
juice or 6 capsules containing cranberry extract daily [36].
Compared with historical controls, the incidence of UTI was
Table 1. Summary of prospective studies evaluating prophylaxis of urinary tract infection (UTI) on bacteriuria.
Study
Year of
study Method Population Intervention Outcome
Stothers et al. [31] 2002 Randomized, placebo-controlled,
double-blind
150 women with previous UTI Placebo juice/tablets vs. placebo juice/
cranberry tablets vs. cranberry juice/
placebo tablets; tablets were given
b.i.d., and juice was given as 250 mL
pure unsweetened product, t.i.d.; 1 year
trial
A significant reduction in UTI: 18% for cranberry
tablets vs. 20% for cranberry juice vs. 32%
for placebo
Kontiokari et al. [32] 2001 Open, randomized 150 women with previous UTI 50 mL cranberry-lingonberry concentrate
vs. 100 mL lactobacillus drink vs. no
intervention for 6 months
A significant reduction in UTI: 16% for cranberry
vs. 39% for lactobacillus and 36% for no
intervention
Kirchhoff et al. [33] 2001 Nonrandomized, controlled 2 geriatric units Cranberry juice vs. usual mixed berry
juice; mean stay, 4 weeks
No effect on UTI
Schlager [34] 1999 Randomized, double-blind, cross-over 15 children with neurogenic bladder 300 mL cranberry concentrate vs.
placebo, each for 3 months
No benefit in preventing UTI or bacteriuria
Walker et al. [35] 1997 Randomized, double blind, cross-over 19 women with recurrent UTI
(10 finished the study)
Cranberry capsule with 400 mg
of cranberry solids vs. placebo, each
for 3 months
Cranberry effective in preventing UTI: of 21
UTIs, 6 UTIs were in the cranberry group
and 15 were in the placebo group
Dignam et al. [36] 1997 Nonrandomized, historical controls 538 nursing home residents 220 mL of cranberry juice or 6 capsules
with cranberry extract per day
Compared with historical controls, incidence
of UTI significantly reduced, from 27 cases
per month to 20 cases per month
Foda [37] 1995 Randomized, single-blind, cross-over 40 children with neurogenic bladder
(21 finished)
Cranberry cocktail, 15 mL/kg/d, vs. water,
each for 6 months
No benefit in preventing UTI or bacteriuria
Avorn [38] 1994 Quasi randomized placebo-controlled,
double-blind
153 elderly women 300 mL of cranberry juice cocktail vs.
placebo for 6 months
Bacteriuria and pyuria were significantly reduced:
28% of samples from placebo recipients vs.
15% of samples from cranberry patients
Haverkorn and Mandigers [39] 1994 Quasi randomized cross-over 38 elderly men and women
(17 finished the study)
15 mL of cranberry juice mixed with water
b.i.d. vs. water, each for 4 weeks
7 of 17 patients had reduction of bacteriuria
during cranberry period
Papas et al. [30] 1966 Nonrandomized 60 patients (73% women)
with bacteriuria
480 mL of cranberry juice for 21 days Positive response in 53% of cases and modest
response in 20%
Cranberry and Urinary Tract Infection • CID 2004:38 (15 May) • 1417
significantly reduced, from 27 cases a month to 20 cases a
month.
Two studies have evaluated the potential of cranberry in
pediatric patients with medical conditions predisposing them
to UTI. These trials did not show any benefit of cranberry for
prevention of UTI or bacteriuria. In the crossover, placebo-
controlled, double-blind study of Schlager et al. [34], 300 mL
of cranberry concentrate provided for 3 months did not have
any benefit when provided to 15 children with neurogenic blad-
der receiving intermittent catheterization. Frequency of bac-
teriuria was 75% during both placebo and cranberry periods,
and the number of UTIs was not significantly different either.
In a similar patient population, Foda et al. [37] administered
water or cranberry cocktail (15 mL/kg/d) to 40 children for 6
months, and the reverse for an additional 6 months. Only 21
patients finished the study. Cranberry had no effect on the
frequency of UTI or bacteriuria. Two additional studies were
performed in adult patients, but neither study evaluated clinical
outcomes. In 8 adult patients with multiple sclerosis random-
ized to receive 20 days’ therapy, cranberry increased acidity of
urine, and in 15 patients with spinal cord injury, cranberry
reduced bacterial biofilm load in the bladder [41, 42].
Jepson et al. [43] reviewed in the Cochrane Library all ran-
domized or quasi-randomized controlled studies for the pre-
vention of UTI with cranberry juice. Until 2000, only 5 trials
met all the criteria adopted for evaluation. (These 5 trials are
discussed above.) The conclusion of the review was that because
of the small number and poor quality of trials, there is insuf-
ficient evidence to show the effectiveness of cranberry juice for
prevention of UTI. However, the Cochrane reviewer did not
include the latest 2 studies by Stothers [31] and Kontiokari et
al. [32]. Both studies were randomized and large, and they
found that women with previous UTIs who took cranberry
products as prophylaxis experienced fewer recurrent UTI. On
the basis of these 2 trials, a recent evidence-based answer pub-
lished in the Journal of Family Practice [44] suggested that a
trial of cranberry juice (3 glasses daily) was reasonable for
women with recurrent UTI who are being considered for an-
tibiotic prophylaxis. The author of the “answer” also noted that
“no national practice guidelines have recommended cranberry
juice as a preventive strategy for recurrent UTI” [44, p. 155].
However, educational brochures published by the National Kid-
ney Foundation contain statements supporting the possible use
of cranberry juice in helping to prevent the development of
UTI [45].
Evidence regarding the role of cranberries for treating, rather
than preventing, UTI is almost nonexistent. The same Cochrane
reviewer who evaluated UTI prevention also systematically re-
viewed the literature for trials that evaluated use of cranberries
for treating UTI [46]. As mentioned above, Papas et al. [30]
studied patients with bacteriuria, but this was not a randomized
trial. Another nonrandomized study [47] found decreased leu-
kocyte counts in urine samples obtained from handicapped
children (most with indwelling catheters) who drank cranberry
juice. This, too, was not a randomized trial.
UTI treatment. The Cochrane reviewers concluded that
randomized studies assessing effectiveness of cranberry juice
for treatment of UTI have not yet been conducted. Therefore,
at present, there is no evidence to suggest that cranberry juice
or other cranberry products are effective for treatment of UTI.
The safety of cranberries is considered to be excellent. Some
patients may experience a slight laxative effect, depending on
the amount ingested [9, 15, 16]. Nevertheless, at least one au-
thor has warned that ingesting a large amount of cranberries
over a long duration may increase risk of some types of urinary
stones in high-risk patients because of the increased urinary
excretion of oxalate and slight urinary acidification [48].
CONCLUSION AND DIRECTIONS
FOR THE FUTURE
Results of clinical studies suggest a possible clinical benefit of
cranberry juice in preventing UTI in some populations. The
strongest evidence available is for sexually active adult women
with previous UTI. In this population, cranberry appears to be
effective in the prophylaxis of recurrent UTI, although standard
juice cocktail was not specifically tested. In elderly patients,
cranberry consumption reduces the incidence of bacteriuria,
although this is often not treated with antibiotics. In contrast,
none of the randomized clinical studies that evaluated patients
at high risk of UTI—for example, those with neurogenic blad-
der—found cranberries to have a beneficial effect.
In the population that benefits most from the prophylactic
effect of cranberry intake (sexually active women with recurrent
UTI), trial results repeatedly show an ∼50% reduction in disease
morbidity. From a clinical point of view, this is quite a modest
benefit, considering the accompanying burden of long-term
daily intake of the compound. Not less significant is the in-
convenience associated with the amount of juice required to
assure continuous availability and the need to carry a daily
supply if twice- or thrice-daily dosing is needed to work, busi-
ness, or vacation travel. If one considers the understandably
high rate of dropouts, the 50% efficacy rate may drop to a
remarkably lower effectiveness.
Furthermore, results of the reviewed studies should not be
viewed as conclusive because many of the trials suffer from
various limitations, including lack of randomization, no or im-
proper blinding, small number of subjects, short trial duration,
large number of dropouts, and no reported intent-to-treat
analysis [43]. Perhaps the single most consistent limitation of
these trials is the lack of uniformity regarding the intervention,
including the particular cranberry product evaluated (juice,
1418 • CID 2004:38 (15 May) • Raz et al.
sweetened cocktail, or capsules/tablets), concentration, dosing
regimen, and duration of the intervention, which greatly dif-
fered from study to study [43, 49]. Further properly designed
trials addressing these issues are needed [38].
Future trials should also assess patient acceptability of treat-
ment. Some studies have indicated that the taste and caloric
load of cranberry juice cocktail is unacceptable to many pa-
tients, especially over the long term [15, 40, 44]. Capsules of
cranberry concentrate could be a better-tolerated alternative
[31]. Cost is another issue that affects patient uptake of treat-
ment, because cranberry products are not currently covered by
health insurance [44, 49]. In the single trial that evaluated the
issue of cost, Stothers [31] found that cranberry tablets are
more cost-effective than organic cranberry juice.
Therefore, the potential of cranberry products to act as a
nonantibiotic alternative for preventing UTI, thereby reducing
the total amount of antibiotics prescribed for UTI, could have
great public health significance. In November 2002, the Na-
tional Center for Complementary and Alternative Medicine, a
branch of the US National Institutes of Health, announced an
initiative to fund research on the role of cranberry in promoting
urinary tract health [50]. As antimicrobial resistance continues
to climb, the time is ripe to recognize the importance of further
cranberry research.
Acknowledgments
We thank Frances Nachmani, Hana Edelstein, and Miriam
Ben-Yashar for their assistance in data collection and processing.
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