The news that America is becoming an obese nation has sunk in to public awareness, and the rise of diabetes and high blood pressure, both exacerbated by being overweight, has also been well-advertised. But there is a hidden danger that gets very little attention: chronic kidney disease (CKD). CKD is the slow loss of kidney function over time. Its prevalence is more alarming than the general public realizes.
There are two reasons for this. The first is that the kidneys can function without noticeable symptoms even when they have lost a great deal of function up to 90 percent. The second is that when symptoms do appear, they are diffuse and hard to pinpoint. The most common are
- Fatigue and weakness
- Headaches
- Loss of appetite, nausea
- Weight loss
- Dry, itchy skin
How many people suspect a problem with their kidneys when these symptoms appear? Yet CKD is a very common disease. In this country, it affects more than 10 percent of the adult population -- that's more than 20 million people. Of these, more than half a million are being treated for kidney failure, also called end-stage renal disease. By some estimates, low-level kidney disease is the most common disorder among older people that goes undiagnosed.
The reason to bring up America's weight problem is that the two leading causes of CKD are diabetes and hypertension, both of which are often related to obesity. They constitute to two leading causes of CKD when other links, such as urinary obstruction or nephritis -- inflammation of the kidneys -- aren't present. Kidney disease is progressive, starting off at an acute stage and then becoming chronic. The disease is incurable, yet the good news is that losing weight, reducing the risk of diabetes and hypertension, is a good course of prevention.
It's remarkable how our kidneys, which we rarely think about, are connected to the body's overall intelligence. Your kidneys are fist-sized, bean-shaped organs found toward the back of your upper abdomen, tucked under the rib cage. The kidneys' main job is to filter the blood of impurities, but they do a remarkable number of other tasks as well.
First, they filter over 50 gallons of blood per day to remove toxins and metabolic wastes along with excess water while returning needed substances back to the blood. Wastes leave your body when urine is passed. The actual filtering process is nowhere near as simple as, say, the water filtration that keeps drinking water pure.
The functional units of the kidney are its nephrons, extremely fine blood-filtering tubules, about 1-2 inches long. Each kidney contains over a million nephrons. At the end of each is a cluster of tiny capillaries called the glomerulus. In the glomerulus fluid filters out of the blood, leaving behind the red and white corpuscles, and passes through the inner wall of the capsule into the nephron tubule. As it does, specific substances are secreted into it while others, like water, are selectively reabsorbed. The end product is urine.
Why does your blood need filtering? Not just waste is involved. The kidneys perform the vital job of maintaining the body's acid-alkaline balance, called its pH. Blood pH needs to be held in a narrow range, slightly alkaline but close to neutral. The kidneys do this job by providing the blood with a buffer solution that compensates for any rise or fall in the level of acidity or alkalinity caused by diet or stress. This buffer solution contains fluids as well as vital salts, called electrolytes, including sodium, potassium and calcium. In a sense your body is like a car battery, which also depends on electrolytes to produce electrical current. But a battery is static while your body is dynamic. Electrolyte levels of are continually adjusted as needed to maintain pH.
The kidneys also produce hormones, like renin, which helps to control blood pressure, and erythropoietin (EPO), that stimulates the production of red blood cells. Loss of kidney function, then, will be felt in every cell of the body. Because of their delicacy, the capillaries in the glomeruli are vulnerable. The high blood sugar in diabetes are toxic to these capillaries, creating them to develop tiny holes through which toxins can escape. Increased fluid pressure due to hypertension causes the walls of the blood vessels to thicken and the glomeruli lose their ability to filter blood.
The patient may be unaware of any symptoms, but as kidney function declines, along with proper pH and hormone balance, your cells detect the change. Damaged kidneys can't produce enough of the hormone EPO to create an adequate number of red blood cells, for example, and the result is anemia. The heart tries to compensate for this lack by pumping harder. Over time, the heart muscle becomes larger but weaker and starts to pump inefficiently. A damaged heart can no longer pump sufficient amounts of blood to the body's tissues. Edema (fluid waste) begins to back up into the lungs, and it becomes difficult to breathe. The final result is congestive heart failure.
Tests for kidney disease check the blood or urine for substances that are normally missing or found only in minute amounts, such as protein and nitrogen. How well the kidneys are filtering can be estimated by measuring how much of these substances is present. Other CKD tests look for chemical imbalances or anemia.
CKD can't be cured, but it can be prevented, and if caught early on, its progression can be slowed or stopped altogether.
1. Food for CKD
One of the most challenging aspects of having CKD is learning what foods you need to avoid and what you can eat, and in what amounts. As CKD progresses, your kidneys lose the ability to balance electrolytes and to eliminate excess water. For this reason, some foods you probably think of as being healthy, such as certain fruits and vegetables, nuts and legumes, may have to be limited or avoided.
It's extremely helpful to consult with a registered dietitian to create an individualized diet, which should include foods you like as well as nutrients you need.
SALT
Too much salt can cause fluid to build up in your tissues, creating swelling. Avoid foods high in salt, such as many canned foods, salty snacks, cured foods like ham and pickles, luncheon meats, and fast foods. Always check nutrition labels for sodium content.
PHOSPHOROUS
Too much phosphorous in the blood causes levels of calcium to decrease. To compensate, the body starts pulling calcium from the bones, weakening them. High-phosphorous foods include certain (not all) dairy products, organ meats, beans and legumes, nuts and seeds, and sodas.
POTASSIUM
Excess potassium can cause an irregular heartbeat or heart attack. Potassium-rich foods include many fruits (such as avocado, apricots and oranges) and vegetables (including squash, carrots and tomatoes), as well as nuts and seeds.
PROTEIN
Protein digestion creates waste products that the kidneys must dispose of. For people not on dialysis, a low-protein diet can help minimize the amount of protein waste products. People on dialysis, on the other hand, lose muscle tissue. To counteract that loss, they need to eat a high-protein diet that includes lots of meat, fish, and eggs, or vegetable-derived protein.
CARBOHYDRATES
People who are overweight or have diabetes or risk factors for diabetes should limit carbohydrates. Otherwise, they are a good source of energy, as long as you don't overdo it. Desserts made with dairy products, chocolate, nuts, or bananas should be limited.
2. Fluids
Most people who have early-stage CKD can drink plenty of fluids. But as kidney disease progresses, the kidneys become unable to remove enough water from the bloodstream. Fluid builds up in the body, blood volume increases and the heart becomes overworked.
Tell your doctor if you are producing either more or less urine than you used to, if you have any swelling in your extremities or abdomen, or if the skin around your eyes is getting puffy.
3. Exercise
Loss of muscle tissue, fatigue, weakened bones, and lack of appetite are some of the worst side effects of CKD. Exercise can prevent or modify these side effects.
Aerobic exercise is physical activity, such as a brisk walk, that raises your heart beat and respiration rates over an extended period of time. Aerobic exercise strengthens your heart, lowers blood sugar levels, improves your appetite and gives you more stamina.
Anerobic exercise is short-term activity that uses up oxygen very quickly, such as weight training. Anerobic exercise builds up muscle tissue and counteracts the loss of muscle that often accompanies CKD. It can help to boost bone density as well.
It's especially beneficial to combine aerobic exercise with anerobic exercise, because building up your muscles helps you to perform both everyday activities and aerobic exercise better.
4. Other lifestyle measures
Weight loss
Taking off even modest amounts of excess weight can help to protect your kidneys. Losing as little as 10 lbs. can lower blood pressure. Losing 5-10 percent of body weight significantly reduces blood sugar levels. Plus, being at a normal weight lowers the strain on your heart and allows it to pump more easily and efficiently.
Smoking cessation
Smoking fills your kidneys with toxic heavy metals, including cadmium and lead, and damages all your blood vessels, large and small.
Stress management
Unmanaged stress raises blood pressure and damages blood vessels. Find ways to unwind if you're chronically stressed.
Because alert management works for many people, and since CKD is associated with diabetes and hypertension, two disorders that need to be prevented for many other reasons, most of us shouldn't focus on our kidneys directly. End-stage treatments, which involves dialysis or even a kidney transplant, are extreme cases. The main reason I bring up CKD is that it is too often overlooked in older people and secondly, because the more we know about the body's astonishing interwoven intelligence, the more true it is that prevention is vitally necessary for good health over the long lifetime that most of us are anticipating.
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