How cranberry works
Tamms-Horsfall glycoprotein, a natural substance present in the urine of some individuals, has the ability to attach itself to the E. coli bacteria and inhibit them from attaching to the bladder wall. Individuals with enough Tamms-Horsfall glycoprotein are unlikely to get a urinary tract infection from E. coli. However, those who lack or have low levels of this natural substance are more susceptible.
In 1994, researchers at Weber State University in Utah discovered that cranberry contains a substance similar in activity to the Tamms-Horsfall glycoprotein. While they have yet to release the substance name until they obtain patent rights, general information is available about how it works. Much like natural glycoprotein, the substance can inhibit the attachment of E. coli bacteria to the bladder wall. In tests where cranberry was added to a petri dish along with E. coli bacteria and bladder cells, the addition of the cranberry substance kept the bacteria from attaching to bladder cells.
Additionally, a 1994 Harvard University study involving 153 elderly women with histories of repeated urinary tract infections showed that regular consumption of cranberry juice cocktail can decrease the incidence of urinary tract infections. In a clinical trial yet to be published from Weber State, the same conclusion was drawn using a concentrated cranberry product. This product, in dehydrated, capsule form, is equivalent to twelve to sixteen 6-ounce glasses of cranberry juice.
Our bodies do have natural barriers against urinary tract infections. In men, the urethra is up to 10 inches long with natural bends, both of which make it difficult for bacteria to reach the bladder. In females, the perineum helps prevent bacteria from entering the urethra. Females are at a disadvantage, however, because the perineum can be damaged or irritated by tight clothing, intercourse, poor hygiene, or bubble baths, and thus allow bacteria to make their way to the bladder. In addition, the female urethra is only 2 inches long and straight, making it easy for bacteria to reach the bladder. If a female infant or young girl has had two or three infections, X-rays of her urinary tract are in order to rule out possible anatomical abnormalities. In the case of young boys, X-rays are in order with the first infection to ascertain whether the urinary tract is intact and functioning properly.
Females also are more likely than males to get a second urinary tract infection, and within as little as two weeks of the first flare-up. During the initial infection, the lining of the bladder is injured, making it more susceptible to new E. coli seeking to attach themselves before the lining has a chance to heal. As such, some women have recurrent urinary tract infections simply because their bladder never really has a chance to heal.
When I see a patient with an acute (recent) urinary tract infection, I use several avenues of treatment. This may include a single or one-day dose of antibiotic to kill existing bacteria. I combine this with one pill of a concentrated cranberry capsule two times a day for at least one month to protect the bladder against reinfection while it heals. Alternatively, a short-term dose of a natural substance such as thyme (Thymus spp.), goldenseal (Hydrastis canadensis), or queen of the meadow (Filipendula ulmaria) can be taken instead of antibiotics to eliminate bacterial growth in the bladder.