Cranberry

Cranberry is a member of the same family as bilberry and blueberry. It is from North America and grows in bogs. The ripe fruit is used medicinally.

In traditional North American herbalism, cranberry has been used to prevent kidney stones and "bladder gravel" as well as to remove toxins from the blood. Cranberry has long been recommended by herbalists as well as doctors to help prevent urinary tract infections (UTIs).

In test tube studies, cranberry prevents E. coli, the most common bacterial cause of UTIs, from adhering to the cells lining the wall of the bladder. This anti-adherence action is thought to reduce the ability of the bacteria to cause a UTI.^{1, 2} The proanthocyanidins in the berry have exhibited this anti-adherence action.³ Cranberry has been shown to reduce bacteria levels in the urinary bladders of older women significantly better than placebo, an action that may help to prevent UTIs.⁴ A small double-blind trial with younger women ages 18–45 years with a history of recurrent urinary tract infections, found that daily treatment with an encapsulated cranberry concentrate (400 mg twice per day) for three months significantly reduced the recurrence of urinary tract infections compared to women taking a placebo.⁵ Other preliminary trials in humans suggest cranberry may help people with urostomies and enterocystoplasties to keep their urine clear of mucus buildup and possibly reduce the risk of UTIs.⁶ However, one trial found that cranberry did not reduce the risk of UTIs in children with neurogenic bladder disease (a condition that does not allow for proper flow of urine from the bladder) who were receiving daily catheterization.⁷

One capsule of concentrated cranberry juice extract (400 mg) can be taken two times per day.⁸ Several 16-ounce (500 ml) glasses of high-quality unsweetened cranberry juice from concentrate each day approximate the effect of the cranberry extract. Cranberry tincture, 1/2–1 teaspoon (3–5 ml) three times per day, can also be taken.

Cranberry concentrate has not been reported to cause side effects and has no known contraindications to use during pregnancy and breast-feeding. According to one report, supplementation with an unspecified number of cranberry tablets for seven days increased the urinary excretion of oxalate by 43%, suggesting that long term use of cranberry supplements might increase the risk of developing a kidney stone.⁹ On the other hand, in the same study, urinary excretion of magnesium and potassium (which are inhibitors of stone formation) also increased. Until more is known, individuals with a personal or family history of calcium-oxalate kidney stones should consult a doctor before using cranberry supplements for long periods of time (e.g., more than a week). Cranberry should not be used as a substitute for antibiotics during an acute urinary tract infection, except under medical supervision.