Cranberry is an evergreen shrub that is grown in North America and Europe. The processed fruit and juice, both rich in vitamin C, are widely consumed as food. The juice extract is marketed as a dietary supplement for urinary tract health and to prevent urinary tract infections (UTIs). It has also been used for oral and gastrointestinal infections, cardiovascular diseases, and against cancer. In preclinical studies, cranberry juice extracts and constituents exhibited antibacterial ⁽¹⁾, antimicrobial ⁽⁴⁵⁾, antifungal ⁽⁴⁶⁾, anti-inflammatory ⁽⁴⁷⁾, antioxidant ⁽⁴⁸⁾, and antiadherence ⁽⁴⁹⁾ properties.

Clinical studies demonstrate that cranberry extracts can help prevent UTIs in adults ^(2) (3), children ⁽⁴⁾, in prostate cancer patients undergoing radiation therapy ^(5) (50), and in patients following urostomy ⁽⁶⁸⁾. A large double-blind study of older adults with high-baseline UTI risk also showed benefit ⁽⁵¹⁾, but another similar study reported negative findings ⁽⁵²⁾. A subsequent analysis revealed increased costs with no meaningful reduction in UTI rates in a geriatric nursing home environment ⁽⁵³⁾. Studies of cranberry juice for recurrent UTIs have also been mixed, with one study finding no benefit among college-aged women ⁽⁶⁾, and another observing significant reductions in UTI relapse in women over age 50 ⁽⁵⁴⁾. Cranberry was not as effective or cost-effective as trimethoprim-sulfamethoxazole in preventing UTIs in premenopausal women, but patients were less likely to develop antibiotic-resistant bacteria ^(8) (55). In volunteers from different regions, anti-adhesion activity with cranberry powder was found to be dose-dependent ⁽⁷⁾ . Overall, a systematic review determined that cranberry juice was more effective than capsules or tablets  ⁽⁵⁶⁾, but despite some support for recurrent UTI prophylaxis ⁽⁶⁹⁾, there is not enough evidence to recommend cranberry juice for UTI prevention ^(9) (70).

In other studies, cranberry juice inhibited the adhesion of H. pylori to human gastric mucosa ⁽¹⁸⁾, and regular consumption may suppress H. pylori infection ^(19) (20), a major factor in peptic ulcer disease and gastric cancer. When used with standard treatment, cranberry juice helped eradicate H. pylori ⁽²¹⁾. It was shown to prevent plaque formation and the development of gum disease as well due to its anticolonizing and antiadhesion properties ^(22) (23).

Cranberry extracts and proanthocyanidins also exhibited antiproliferative effects against prostate ^{(10) (11) (12)}, liver ⁽¹³⁾, lung ⁽⁵⁷⁾, neuroblastoma ⁽⁵⁸⁾, breast ⁽¹⁴⁾, ovarian ⁽¹⁵⁾, gastric ⁽⁵⁹⁾, colon ^(12) (16), esophageal ⁽⁶⁰⁾, and oral ⁽¹²⁾ cancer cells. Although cranberry juice consumption did not lower oxidative status in humans, suggesting lack of protective effect against cancer or heart disease ⁽¹⁷⁾, it did appear to improve cardiovascular disease (CVD) risk factors in diabetic men ⁽⁶¹⁾. However, cranberry juice has high concentrations of oxalate, a common component of kidney stones, and should be limited in patients with a history of nephrolithiasis ⁽⁴⁰⁾. Other data suggest it may be helpful in uncommon forms including struvite stones, which are associated with bladder infections ^{(33) (62) (63)}.