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High School Chemistry and Kidney Disease (part 2)

Published: June 18, 2010

We left off chatting about renal stones and what one can do to prevent them from coming back. Having endured a long airplane ride with flank pain that was horrid despite the vicodin, I am keen to avoid another such episode.

The logic of cutting down calcium as means of prevention made sense, but it wasn’t the whole story. The trick of biochemistry is to stop calcium from precipitating in your urine, where the scraping of little internal rocks as they follow the flow of liquid headed for the bladder makes a person remarkably uncomfortable.

This process is combated by keeping the calcium from combining with things that form rocks in the urine. Dilution of urine is your best friend in this effort. The most avoidable problem is low urine output (and thus concentrated urine) from under hydration. The goal is to produce about 2 quarts of urine a day. If your kidneys are flushing you out at that rate, the urine is thought to be properly dilute. Surprisingly, not all liquids are equal in hydration. The worst choice turns out to be grapefruit juice. For reasons still not clear something in grapefruit increases your odds of forming stones. The best (after water) may be lemon juice, or lemonade. Lime juice/limeade also makes a good choice. Citric acid is found in the aptly named citrus fruits, and citrate happens to be a potent inhibitor of stone formation. So, this is one form of preventative therapy that is pretty palatable. Sorry about that grapefruit fans.

The bottom line is, if you are apt to reducing the risk of kidney stone formation, there are several things you can do. Lowering one’s sodium helps, and limiting animal protein to one meal a day seems a reasonable goal. Drinking enough to form 2 liters a day is a fine idea – though who measures? Urine color is a simpler gauge. If its bright yellow and you are not producing much urine; well then have a few extra glasses. Water is fine, but lemonade will have some added benefits. And as we said in part one, cutting calcium down is apparently NOT the way to go.