Top Five Myths About Human Kidneys

Kidneys are not our most glamorous organs, often taking a back seat in the news to the brain or the heart. Probably the only time we think about our kidneys is when we joke about selling one to afford the newest Apple gadget.

But the two bean-shaped, fist-sized kidneys sitting at the base of the rib cage are fascinating, multitasking organs. They are at work all day long removing waste, stimulating red blood cell production and keeping the body's balance of salts, acids and bases in check.

Kidneys are also quite resilient. Even if you lose or donate one kidney, you can continue to live a normal, healthy life with the other. But most of us don’t understand this complex organ very well, giving birth to misconceptions about how our kidneys work and what ails them. Here are the top five myths about human kidneys:

1. Drinking lots of water will flush out toxins

Drink at least six to eight glasses of water to detox. We’ve heard this over and over again. But there is little scientific evidence to support it. All that chugging a lot of water does is increase the volume of urine that you excrete, according to Stanley Goldfarb, a kidney expert at the University of Pennsylvania. The kidney is a complex filter, “and how much water you drink does not affect how well this filter works,” Goldfarb says.

There are some exceptions. For instance, if you have a history of developing kidney stones, then it is important to drink plenty of water to prevent future pain, says Robyn Langham of St. Vincent’s Hospital in Melbourne, Australia. You also need to drink more water if you live in extreme weather conditions that can make you dehydrated quickly, she adds. “Otherwise, drinking more water is not going to help your kidneys work any better or any worse.”

So where did this popular misconception begin? “I think this information has stemmed from the bottled water industry’s need to sell more,” Langham says.

2. A high-calcium diet can cause kidney stones

Most kidney stones are made of calcium. So it is not surprising that many of us think avoiding milk or a diet rich in calcium will help prevent painful kidney stones from forming. However, it is not excess calcium that can get us in trouble, but the lack of it.

“Dietary calcium actually protects against kidney stones,” says Matthew Sparks of Duke University School of Medicine. The most common type of kidney stone is made up of two components: calcium and oxalate, a substance found in many vegetables and fruits. When oxalate accumulates in the urine, it can combine with calcium filtered from the bloodstream to form kidney stones.

Calcium in our diet can prevent that from happening. It can bind with oxalate within the gut itself, and then the body can safely eliminate it via feces. Oxalate can no longer get absorbed into the bloodstream, make its way to the kidneys and form stones. But Sparks warns that while calcium-rich food can be good for kidneys, calcium supplements may not. “This form of calcium does not bind oxalate as voraciously and is actually absorbed into the bloodstream, where it is excreted into the urine.”

3. Drinking alcohol will damage your kidneys

You’re at a pub, drinking beer. Then you have the urge to pee. As the evening progresses, you spend most of your time in the toilet. So it might be easy to think that alcohol is bad for your kidneys because you’re overworking them.

As it turns out, there isn’t much evidence to back this up. There’s a risk of liver disease, but not kidney damage if you drink moderate amounts of alcohol, says Goldfarb. For instance, a 2014 paper that reviewed several studies found no conclusive evidence of either harmful or beneficial effects of moderate alcohol consumption on kidney function.

But let’s not get complacent. Binge drinking regularly is probably not a good idea. Guzzling down large quantities of alcohol, like anything else, can be harmful, says Sparks. Drinking alcohol can also make people dehydrated because it makes the body lose more fluid via pee than we normally would. “So the advice is to drink a glass of water between every glass of alcohol,” says Langham.

4. If you have kidney disease, you will know it

Kidney diseases can be deceptive. Unlike heart diseases, physical symptoms of kidney damage are subtle. For instance, kidneys rarely hurt unless you have kidney stones or an infection, says Langham. Moreover, how much you urinate doesn’t tell you a whole lot about your kidney health, she adds. “Often, the ability to make urine goes on for a very long time even after the kidneys have failed. So if you’re still making urine, that doesn’t necessarily tell you what your kidney function is like.”

If someone does have a failing kidney, they may not even know it about it until only 10 to 15 percent of kidney function remains. And this makes studying kidney diseases difficult, according to Sparks. But there are ways to keep a check on your kidneys. A simple blood test can measure the levels of toxins and waste products in the bloodstream and tell doctors how efficiently the kidneys are working.

Similarly, a urine test can detect and measure certain proteins in urine that shouldn’t be there if the kidneys were functioning properly. Blood pressure is also a good indicator of risk, says Langham. Among their many tasks, kidneys release hormones that help regulate blood pressure. “As kidneys get damaged, you develop high blood pressure, and as you get high blood pressure, you can damage your kidneys,” adds Langham.

5. Kidney diseases cannot be prevented

Even medical practitioners can fall victim to this misconception, says Langham. But many kidney diseases can be prevented, or at least slowed down, if people are aware of the factors that can put them at risk, she adds. Diabetes and high blood pressure, for instance, are associated with most kidney diseases. According to the Centers for Disease Control and Prevention, 1 out of 3 adults with diabetes and 1 out of 5 adults with high blood pressure in the U.S. has chronic kidney disease.

“So if one can control these, that’ll reduce the risk of kidney diseases,” Goldfarb says.

Old age, smoking cigarettes and obesity puts people at risk too. Keeping an active lifestyle filled with exercise, proper hydration and a healthy diet is important, Sparks adds. Moreover, if you have a family history of kidney diseases, regular checkups can be useful in detecting kidney damage early on, according to Langham.