Do you ever contemplate your kidneys? Join the club if you answered “no.” After all, why would you pay them any attention if they don’t cause you any problems? Whether you think about them or not, each day, these important organs filter 200 liters of blood, sifting out about 2 liters of waste and water that your body excretes as urine. “Kidneys usually work in the background,” says Jacquelyn Wilson, MD, a homeopathic doctor in San Diego. Called the “biochemists of the body,” these bean-shaped organs are about the size of your fist and sit on either side of your spine at the small of your back. Each one contains about 1.5 million filters that balance the electrolytes (sodium, phosphorous, and others) in your blood, regulate the amount of fluid in your system, and clean out waste—by-products from your muscles, acids from foods you’ve eaten, and leftover chemicals that your body produces as you burn fat. As if all this weren’t enough, your kidneys are also little hormone factories that affect the health of your blood, bones, and heart, releasing the following:
>> Erythropoietin (EPO). When kidney cells sense that the body’s oxygen levels are low, they release more EPO, which stimulates the bone marrow to make more red blood cells to help carry more oxygen to the entire body. So if the kidneys don’t work properly, your body doesn’t get enough oxygen. The result? Anemia.
>> Calcitriol. Your bones need the kidneys to produce enough of this active form of vitamin D (actually a hormone) so that they maintain proper calcium levels.
>> Renin. Not a hormone per se, but an enzyme that eventually produces the hormone angiotensin II. This hormone, in a roundabout way, causes the kidneys to retain more water and salt, increasing blood pressure when it drops too low.
The most important thing to remember about your kidneys is that they exist to maintain homeostasis—fluid balance—in the body. For example, if your blood pressure increases, the kidneys kick into gear to excrete more water and salts so that the volume of blood goes down and your blood pressure decreases. If your blood pressure gets too low, the kidneys decrease the amount of water and salts they excrete so blood volume goes up and blood pressure increases.
When Good Kidneys Go Bad
Unfortunately, most people don’t learn about kidney problems until it’s too late, because most kidney diseases don’t produce any symptoms, says Leslie Spry, MD, of the National Kidney Foundation. Chronic kidney disease (CKD)—abnormalities in kidney or urine function for three months or more—has become more prevalent in the past 10 years. The rise in CKD, now the ninth leading cause of death in the US, may correlate with the national increases in diabetes, high blood pressure, and obesity. Why? Because diabetes prevents glucose from breaking down, and the excess glucose can damage the nephrons, the part of the kidney responsible for purifying and filtering blood. Chronic high blood pressure can damage blood vessels throughout the body, including in the kidneys, making it more difficult for the kidneys to remove waste and fluids.
Researchers aren’t quite sure why obesity plays a role, but a 2006 study published in the Annals of Internal Medicine found that even people who are moderately overweight are seven times more likely to have kidney failure than their thinner counterparts. The research suggests that obese people are more likely to get diabetes or suffer from high blood pressure, but even more than that, “Obesity places more metabolic demand on the kidneys, forcing them to work harder,” says Chi-yuan Hsu, MD, assistant professor of medicine at the University of California, San Francisco and lead author of the study. Other reasons for kidney failure include autoimmune disease, taking NSAIDs (nonsteroidal anti-inflammatory drugs) for several years, and inflammation.
Generally speaking, kidney failure happens gradually, over many years—unless, of course, you’ve been poisoned or have had a physical injury to the kidney area. If your kidneys are failing, symptoms may include fever or chills, swelling of your ankles, puffy eyes, fatigue, weight loss, dark urine, abdominal pain, itching, or pale skin. But most of the time you won’t experience anything at all. In fact, says Kelly Welsh, a Milwaukee-based dietician specializing in kidney health, “symptoms don’t appear until 60 to 70 percent of kidney function is lost.”
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What You Can Do Now
While you can’t prevent your kidneys from aging (like everything else), you can slow down the process. Of course, the healthier you are in your younger years, the healthier your kidneys will be when you’re old and gray. Here are the Ten Commandments of good kidney health to incorporate into your lifestyle today.