There is some human evidence supporting the use of cranberry juice and cranberry supplements to prevent urinary tract infection (UTI), although most available studies are of lesser quality. Clear dosing guidelines are lacking, but given the safety of cranberry, it may be reasonable to recommend the use of moderate amounts of cranberry juice cocktail to prevent UTI in non-chronically ill individuals.
Cranberry has not been shown effective as a treatment for documented UTI. Although cranberry may be used as an adjunct therapy in some cases, given the proven efficacy of antibiotics, cranberry should not be considered a first-line treatment.
Cranberry has been investigated for numerous other medicinal uses, and promising areas of investigation include prevention of H. pylori infection, which causes gastrointestinal ulcers and dental plaque.
These uses have been tested in humans or animals. Safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider.
Preliminary research suggests that cranberry juice may increase vitamin B12 absorption in patients taking antacids (drugs that reduce stomach acid), such as proton pump inhibitors like lansoprazole (Prevacid®). However, this effect may be due to the acidity of the juice rather than an active component of cranberry itself. Further research is needed before a recommendation can be made.
Research results of cranberry as an antibacterial show conflicting results. Further research is needed before a conclusion can be drawn.
According to laboratory research, cranberry may have antioxidant properties. However, human research is lacking. Further research is needed before a recommendation can be made.
Limited laboratory research has examined the antiviral and antifungal activity of cranberry. There is a lack of reliable human studies supporting the use of cranberry in this area.
Based on a small amount of laboratory research, cranberry has been proposed for cancer prevention. Research is needed in humans before a strong recommendation can be made.
In preliminary human research on patients with coronary artery disease, consumption of cranberry juice reduced the carotid femoral pulse wave velocity, a measurement of arterial stiffness. Further research is required.
There is preliminary evidence that cranberry may be effective in preventing urinary tract infections in children with neurogenic bladder.
Because of its activity against some bacteria, cranberry juice has been proposed as helpful for mouth care. However, many commercial cranberry juice products are high in sugar and may not be suitable for this purpose. There is not enough research in this area to make a clear recommendation.
According to a single trial from a systematic review, effects of cranberry on blood sugar levels in patients with diabetes are lacking. Further research is required.
Based on early research, cranberry may reduce the ability of Helicobacter pylori bacteria to live in the stomach and cause ulcers. Further research is needed to confirm these results.
According to preliminary research, it is not clear if drinking cranberry juice increases or decreases the risk of kidney stone formation. Cranberry juice is reported to decrease urine levels of calcium, increase levels of urine magnesium and potassium, and increase urine levels of oxalate.
The lipid-lowering effects of cranberry were observed in individuals with obesity or diabetes. At this time evidence in support of these effects is lacking. Further research is required.
Preliminary research results show that cranberry juice may increase overall ability to remember. Further well-designed clinical trials are needed to confirm these results.
In early research, cranberry juice lacked effect on cardiovascular disease risk factors in patients with metabolic syndrome. Further research is required.
There is preliminary evidence that cranberry is not effective in preventing urinary symptoms related to pelvic radiation therapy in patients with prostate cancer.
There is preliminary evidence that cranberry juice may reduce urine odor from incontinence or bladder catheterization. Further research is needed before a firm recommendation can be made.
The effect of a cranberry supplement in female surgeons with stress-related disorders has been studied. Although there is evidence of benefit, further research is required.
Cranberry fruit powder improved International Prostate Symptom Score (IPSS) and quality of life in men with lower urinary tract symptoms (LUTS) and presenting with elevated levels of prostate-specific antigen (PSA) and/or benign prostatic hyperplasia (BHP). Further well-designed research is required.
There are multiple studies of cranberry (juice or capsules) for the prevention of urinary tract infections (UTIs) in healthy women, pregnant women, individuals with spinal cord injuries, and nursing home residents. While no single study convincingly demonstrates the ability of cranberry to prevent UTIs, the sum total of favorable evidence combined with laboratory research tends to support this use. It is not clear what dose is best.
Cranberry seems to work by preventing bacteria from sticking to cells that line the bladder. Contrary to prior belief, urine acidification does not appear to play a role. Notably, many studies have been sponsored by the cranberry product manufacturer Ocean Spray®. Additional research is needed in this area before a firm conclusion can be drawn.
There is a lack of well-designed human studies of cranberry for the treatment of urinary tract infections. Laboratory research suggests that cranberry may not be an effective treatment when used alone, although it may be helpful as an adjunct to other therapies such as antibiotics.
In large quantities, cranberry juice may lower urine pH, making it more acidic. Contrary to prior opinion, urine acidification does not appear to be the way that cranberry prevents urinary tract infections. More research is needed in this area.
Although cranberry consumption may increase urinary excretion of oxalate, possibly predisposing to calcium oxalate stone formation, it also increases magnesium and potassium excretion, which may decrease the rate of stone formation. Cranberry juice of unspecified amounts has been found to decrease urinary calcium by 50% in patients with renal stones. The clinical significance and net outcome of these findings in various subgroups has not been elucidated.
It is proposed that skin irritation at urostomy sites may be related to urine pH. Cranberry juice can lower urine pH and has been tested for this purpose. Further research is needed before a recommendation can be made.
* Key to grades
A: Strong scientific evidence for this use B: Good scientific evidence for this use C: Unclear scientific evidence for this use D: Fair scientific evidence for this use (it may not work) F: Strong scientific evidence against this use (it likley does not work)
Tradition / Theory
The below uses are based on tradition, scientific theories, or limited research. They often have not been thoroughly tested in humans, and safety and effectiveness have not always been proven. Some of these conditions are potentially serious, and should be evaluated by a qualified healthcare provider. There may be other proposed uses that are not listed below.
As an antioxidant, 250 milliliters of cranberry juice (Ocean Spray® Cranberry Select) has been taken three times daily for two weeks. Dried cranberry juice (NutriCran®90, Decas Botanical Synergies, United States) two capsules daily (400 milligrams) or two capsules three times daily (1,200 milligrams daily) has been taken for eight weeks.
For cardiovascular disease, 480 milliliters of double-strength cranberry juice (containing 54% juice, 835 milligrams of total polyphenols, and 94 milligrams of anthocyanins) has been used daily.
For diabetes, six capsules containing cranberry juice concentrate powder equivalent to 240 milliliters of cranberry juice cocktail have been used daily for six weeks.
For H. pylori infection, 250 milliliters has been used twice daily for 90 days.
For lipid-lowering effects, six capsules containing cranberry juice concentrate powder equivalent to 240 milliliters of cranberry juice cocktail has been used daily for six weeks. 125-500 milliliters of low-calorie cranberry juice has been used daily for four weeks.
For lower urinary tract symptoms (LUTS), one gelatin capsule containing 500 milligrams of cranberry fruit powder has been used three times daily for six months.
For metabolic syndrome (cardiovascular disease risk factors and antioxidant status), one cup (240 milliliters) of cranberry juice has been used twice daily, as a midmorning and early-evening snack with at least six hours in between doses, for eight weeks (for a total daily dose of 480mL).
For prevention of urinary stones, the following have been used: one quart of cranberry juice cocktail daily; eight ounces of cranberry juice four times daily for several days, then eight ounces two times daily; and one liter of cranberry juice daily for seven days. Efficacy has not been proven for these dosages.
For prevention of urinary tract infections, doses studied range from 30 to 480 milliliters (1-16 ounces) of cranberry juice cocktail 2-3 times daily for up to 40 weeks, or 15-30 milliliters of unsweetened 100% cranberry juice daily. One gram of concentrated cranberry extract (CranVerry, Aim This Way, Cambridge, MA) has been used twice daily for six months, and 1.5 ounces of frozen juice concentrate twice daily has been used. Eight ounces of cranberry juice cocktail (Ocean Spray® low-calorie juice cocktail) was taken twice daily for six months. One to three cranberry capsules (36 milligrams of cranberry proanthocyanidin; PAC) have been taken daily for 30 days. Four to five milliliters of cranberry tincture has been given three times daily (anecdotally). For a novel concentrated cranberry liquid blend (Uti-Stat®), the suggested dose was set at 60 milliliters daily. Supplements containing 200-8,000 milligrams of cranberry have been taken daily for up to six months.
For urinary tract infection treatment, 360-480 milliliters (12-16 ounces) of cranberry juice have been taken daily for up to 21 days.
Children (younger than 18 years)
There is not enough scientific evidence to suggest cranberry supplementation in children (beyond amounts found in a normal balanced diet). Cranberry been used safely in doses of 15 milliliters per kilogram. In children (2-18 years old) with neurogenic bladder receiving clean intermittent catheterization, 300 milliliters daily of cranberry juice for three months was used. High doses may cause toxicity.
The U.S. Food and Drug Administration does not strictly regulate herbs and supplements. There is no guarantee of strength, purity or safety of products, and effects may vary. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy. Consult a healthcare provider immediately if you experience side effects.
Cranberry should be avoided by people with an allergy or hypersensitivity to Vaccinium species (cranberries and blueberries) their parts, or members of the Ericaceae family. People who are allergic to aspirin should avoid drinking large quantities of cranberry juice.
Side Effects and Warnings
Patients with diabetes or glucose intolerance may want to drink sugar-free cranberry juice to avoid a high sugar intake. High doses of cranberry may cause stomach distress and diarrhea, or may increase the risk of kidney stones in people with a history of oxalate stones. Some commercially available products are high in calories. On average, six ounces of cranberry juice contains approximately 100 calories. One study showed the possibility for occurrence of vaginal yeast infections in those women who often consume cranberry juice, although this has not been proven. Use cautiously if taking anticoagulants (blood thinners) such as warfarin, medications that affect the liver, or aspirin. Use cautiously in patients with altered hepatic function or in those taking cytochrome P450-metabolized agents. Use cranberry juice cautiously due to the high sugar content, which may negatively affect dental health. Use cautiously in patients with rheumatoid arthritis, based on the potential for acidic juices to increase joint pain. Avoid in those with known allergy or sensitivity to Vaccinium species (cranberries and blueberries), their parts, or members of the Ericaceae family.
Pregnancy and Breastfeeding
Safety has not been determined in pregnancy and breastfeeding, although cranberry juice is believed to be safe in amounts commonly found in foods. Many tinctures contain high levels of alcohol and should be avoided during pregnancy.
In theory, due to its acidic pH, cranberry juice may counteract antacids. Cranberry juice theoretically may increase the effects of antibiotics in the urinary tract and increase the excretion of some drugs in the urine. Cranberry juice may increase absorption of vitamin B12 in patients using proton pump inhibitors such as esomeprazole (Nexium®).
Some cranberry tinctures may have high alcohol content and may lead to vomiting if used with the drug disulfiram (Antabuse®) or metronidazole (Flagyl®).
Although it is controversial, some studies have shown that taking the prescription blood thinner warfarin (Coumadin®) and cranberry products at the same time can elevate the international normalized ratio (INR), which could increase the risk of bleeding.
Interactions with Herbs and Dietary Supplements
In theory, cranberry juice may increase the excretion of some herbs or supplements in the urine.
Theoretically cranberry products may increase the risk of bleeding in people taking other herbs or supplements like garlic or danshen.
Inhibition of H. pylori bacteria, which may lead to gastrointestinal ulcers, may be increased when oregano and cranberry are taken together.
Acidifiers, Alzheimer's agents, antibacterials, antifungals, antihelminthics (expels worms), antilipemics (cholesterol-lowering agents), antineoplastics (anticancer agents), antioxidants, antiparasitics, antiulcer agents, antivirals, cytochrome P450-metabolized agents (agents broken down by the liver), diuretics, gastrointestinal agents, hypoglycemics (blood sugar lowering), lingonberry, renally eliminated agents (agents eliminated by the kidneys), salicylate-containing agents, vitamin B12.
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The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.