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What is it? Overview Usage Side Effects and Warnings

What is Cranberry?

The cranberry plant is a close relative of the common blueberry. Native Americans used it both as food and for the treatment of bladder and kidney diseases. The Pilgrims learned about cranberry from local tribes and quickly adopted it for their own use. Subsequent physicians used it for bladder infections, for "bladder gravel" (small bladder stones), and to remove "blood toxins."

In the 1920s, researchers observed that drinking cranberry juice makes the urine more acidic. Since common urinary tract-infection bacteria such as E. colidislike acidic surroundings, physicians concluded that they had discovered a scientific explanation for the traditional uses of cranberry. This discovery led to widespread medical use of cranberry juice for treating bladder infections. Cranberry fell out of...

Cranberry is widely used today to prevent bladder infections , although as yet the evidence to support this use remains limited. Contrary to the research from the 1920s, it now appears that cranberry's acidification of the urine is not likely to play an important role in the treatment of bladder infections; current study has focused instead on cranberry's apparent ability to block bacteria from adhering to the bladder wall. 1 If the bacteria can't hold on, they will be washed out with the stream of urine. Interestingly, studies have found that in women who frequently develop bladder infections, bacteria seem to have a particularly easy time holding on to the bladder wall. 2 This suggests that cranberry juice can actually get to the root of their problem.

Just as cranberry seems to...

Safety Issues

As a widely eaten food, cranberry is thought to have a generally good safety profile.

However, several case reports suggest that cranberry could interact with the drug warfarin (Coumadin), potentially leading to internal bleeding. 3 Two formal studies have failed to find evidence of such an interaction, 4 while a third study did find that cranberry can increase the blood thinning effect of warfarin in healthy male subjects. 5 Prudence would suggest caution, especially when consuming more than eight ounces of cranberry juice daily.

In addition, cranberry juice might allow the kidneys to excrete weakly alkaline drugs more rapidly, thereby reducing their effectiveness. This would include many antidepressants and prescription painkillers.

Finally, indirect...