Unsweetened cranberry juice and supplements are lauded as being good for urinary tract health, but how does taking a supplement help? Juice is supposed to make the bladder less hospitable for bacteria, but it’s going right through the bladder and the rest of the urinary tract - so do things other than liquids (like the contents of liquid gel supplements…and what about the ones with powered cranberry instead?) make their way into the bladder too, or is it simply absorbed into the blood stream?
Liquids that are consumed don’t directly go to the bladder. Basically, everything that you eat or drink passes from the small/large intestine into the bloodstream.
As the blood circulates through the body it passes through the kidney. The kidneys filter the blood, and everything they filter out of the blood passes from the kidney, through the ureters (tubes connecting the kidneys and the bladder), and then from the bladder through the urethra (tube to the outside).
Cranberry juice supposedly helps prevent urinary tract infections, but studies are inconclusive/conflicting. According to Wikipedia, a chemical in cranberry juice (proanthocyanidins) may directly affect the surface of bacteria, preventing them from adhering to the bladder and urinary tract. Also cranberry juice is acidic, and when it is filtered by the kidneys is lowers the pH of the urine in the bladder, making it harder for bacteria to live there.
Dietary factors can change the composition of the urine in several ways.
The commonest explanation for the effect of cranberry juice is a change in the pH of the urine from the production of hippuric acid. Acidifying the urine can make it more difficult for common urinary tract pathogens such as E Coli to adhere to the lining of the bladder and gain a foothold.
See here for a sample discussion on some other factors. That particular article is in response to another which talks about how calcium may increase adherence of bacteria…
Another article:
*Nutritional Considerations
The role of diet in the prevention and treatment of urinary tract infection remains unsettled. Some nutritional strategies with anecdotal support (vitamin C, high intake of fluids) have not demonstrated clinical effectiveness. Others, such as cranberry juice, have proven effective in clinical trials.4 Still others, such as probiotic treatment and high–fiber diets, await further evaluation. In epidemiologic or clinical studies, the following factors are associated with reduced risk:
Flavonoid–containing juices. Certain classes of flavonoids (eg, epicatechin) block adhesion of E coli fimbria to uroepithelial cells. They may also prevent UTI by other mechanisms, such as the down–regulation of genes in E coli responsible for fimbrial expression. Epidemiological and clinical studies show that women who consume cranberry or cranberry–lingonberry juices have a 20% lower risk for UTI compared with those not drinking juice, a finding comparable to that of continuous low–dose antimicrobial prophylaxis.4,7*
(sorry; I’m not sure how to fix that link…)
What goes through the bladder?
Kidney stones.
But slowly, and very, very painfully.
it isn’t the bladder part that hurts, it is the ureter and urethra that are the bitch … they just sort of boink around in the bladder.
I was a healthy volunteer in a study of the interaction of hippuric acid in cranberry juice and furosemide. The cranberry juice increased the amount of urine in an 8 hour period.
In the study, First week, I was given 1 liter of cranberry juice over 30 minutes, then 40 mg IV Lasix 30 minutes later.
My urine output was measured and replaced (IV fluids) for 8 hours. Total intake/output was 22 liters.
The second week was the same procedure, but one liter of water, rather than cranberry juice. intake/output was 18 liters in 8 hours.