Cataracts

Blueberries are high in flavonoids called anthocyanosides. Anthocyanosides may protect both the lens and retina from oxidative damage.

Chronic venous insufficiency (CVI)

Proanthocyanidins (also known as oligomeric procyanidins or OPCs), a group of flavonoids found in cranberries and other plants, have been shown to strengthen capillaries in double-blind research. Double-blind trials demonstrating efficacy of proanthocyanidins used concentrated extracts, not whole foods. It is not known if eating cranberries will have any effect on preventing or reversing chronic venous insufficiency.

Prostatitis

Cranberries, which are effective in preventing urinary tract infections, may help reduce the risk of bacterial prostatitis, though no studies have investigated this possibility. Cranberries can be consumed as juice, or taken as concentrated cranberry extracts in capsules.

Urinary tract infections (UTIs)

Modern research has suggested that cranberries may prevent urinary tract infections. In a double-blind study, elderly women who drank 10 ounces (300ml) of cranberry juice per day had a decrease in the amount of bacteria in their urine. In another study, elderly residents of a nursing home consumed either 4 ounces of cranberry juice or six capsules containing concentrated cranberry daily for 13 months. During that time, the number of UTIs decreased by 25%. A small preliminary study with younger women ages 18 to 45 years who had a history of recurrent UTIs found that daily treatment with an encapsulated cranberry concentrate (400mg twice per day) for three months significantly reduced the recurrence of urinary tract infections compared to women taking placebo.

Research has suggested cranberries may be effective against UTIs because they may prevent E. coli, the bacteria that causes most urinary tract infections, from attaching to the walls of the bladder. However, cranberries are not a substitute for antibiotics in the treatment of acute UTIs. Moreover, in children whose UTIs are due to “neurogenic bladder,” cranberry juice supplementation did not reduce the rate of infection. Drinking 10–16 ounces (300–500ml) unsweetened or lightly sweetened cranberry juice per day is recommended by many doctors for prevention and as part of the treatment of urinary tract infections. Alternatively, 400mg of concentrated cranberry extracts twice per day can be used. Cranberries, when eaten as a food, are usually heavily sweetened; such foods are not likely to have any benefit for preventing or treating UTIs.

Blueberries contain similar constituents as cranberries, and blueberries might also prevent bacteria from attaching to the lining of the urinary bladder. However, studies have not yet been done to determine if blueberries can help prevent bladder infections.