As garbage collectors of the body’s waste-filtration system, the job of the kidneys isn’t glamorous. But, as Stevie Bee reports, they play a crucial role in helping us maintain good health.
They’re the body’s true workhorses. The kidneys. Every day they filter close to 200 litres of blood and remove up to two litres of waste and excess water from the bloodstream and, at the same time, balance the body’s fluids. Given they’re about the size of your fist, that’s no mean feat.
The wastes in your blood come from the normal breakdown of active muscle and from the food you eat. After your body takes what it needs from the food, the leftovers are sent to the blood, which is then filtered by the kidneys, with the waste and extra water becoming urine.
Your kidneys measure out chemicals such as sodium, phosphorus, and potassium and release them back to the blood to return to the body. In this way, your kidneys regulate the body's level of these substances. The right balance is necessary for life, but excess levels can be harmful.
As well as removing wastes, your kidneys release three important hormones.
- Erythropoietin or EPO, which stimulates the bones to make red blood cells; without enough blood cells to carry oxygen throughout the body we become anaemic.
- Renin, which regulates blood pressure; and
- Calcitriol, the active form of vitamin D, which helps maintain calcium for bones and for normal chemical balance in the body.
If your kidneys are healthy, you have 100 percent renal function. Some loss of renal function is usual as we age, and small declines don’t cause a problem; in fact, you can be healthy with 50 percent of your renal function if it remains stable. But many people with 50 percent renal function have a kidney disease that will get worse. If you get down to less than 20 percent, you’ll be in trouble; below 10–15 percent, you’ll most likely need either ongoing dialysis or a kidney transplant.
Why do kidneys fail?
Damage to the kidneys can happen quickly, often through injury or poisoning, but most impairment occurs slowly and silently. It may take years or even decades for the damage to become apparent. The two most common causes of kidney disease are diabetes and high-blood pressure.
In fact, the first sign of a kidney problem may be high-blood pressure, a low number of red blood cells (anaemia), or blood or protein in the urine. High-blood pressure can damage the small blood vessels in your kidneys affecting their capacity to filter poisons from your blood as they are supposed to.
Diabetes keeps the body from using sugar as it should. If sugar stays in your blood, instead of breaking down, it can act as a poison. Damage to the kidneys’ nephrons from unused sugar in the blood is called diabetic nephropathy. Keeping your blood sugar levels down can help delay or prevent diabetic nephropathy.
Some over-the-counter medicines can be poisonous to your kidneys if taken regularly over a long period of time. Medicines that combine aspirin, acetaminophen, and other medicines such as ibuprofen have been found to be the most dangerous to the kidneys. If you take painkillers regularly, check with your doctor to make sure you’re not putting your kidneys at risk.
The risk factors for kidney disease in people with HIV include all those listed above. As well, poorly managed HIV infection and coinfection with hepatitis C can also increase the risk of kidney disease in people with HIV. Some HIV medications can also affect the kidneys. The risk of kidney damage is carefully considered by healthcare providers when prescribing HIV medication. If a positive person on treatment shows signs of kidney damage, the doctor will no doubt suggest a change of medicine.
For most people, though, a healthy, balanced diet will keep the kidneys functioning well. Just watch your blood sugar levels and your blood pressure levels. A blood test can indicate whether there’s too much creatinine in your blood, a sign you’re not processing those waste products as urine. If so, your health practitioner can advise a course of action.
Keep your fluids up. The general advice is drink just enough fluids to keep the urine between light to pale yellow (straw-coloured) and colourless. The standard daily recommendation is 13 cups (2.5L) for men and 9 (1.8L) for women. That does include both healthy fluids such as filtered water and the water found naturally in fruits and vegetables. You can drink most beverages on a kidney-friendly diet, but sugary soft drinks and beer both have high phosphorous levels. There is some evidence that cranberry juice can help prevent urinary tract infections, which reduces the strain on the kidneys.
Eat plenty of fruits and vegetables. Many of us fail to eat enough fruits and vegetables, meaning we miss out on the benefits of antioxidants, which help neutralise unstable molecules known as free radicals. These cause inflammation and damage to cells and tissues, including your kidneys, when your antioxidant intake is insufficient. Adding ginger to your diet is a simple and convenient way to boost antioxidant intake; ginger can also improve blood sugar control and may also help reduce the risk of complications from diabetes, such as kidney damage. But you still need the recommended 5–9 servings of fruits and vegetables each day. Fresh produce is not only high in water content, but it also contains important nutrients such as vitamin C and flavonoids that support the health of all your organs, including the kidneys. Your best veggie options include, cabbage, cauliflower, capsicum, celery, asparagus, cucumber, eggplant. Among fresh fruits, you have many tasty low-potassium options, including berries, such as blueberries, blackberries, raspberries and strawberries; peaches; grapes; apples; watermelon.
Watch cholesterol. Excess cholesterol in your blood, which may result from a high-fat diet, can build up on the inside walls of your blood vessels. The build-up makes pumping blood through the vessels harder for your heart. Although scientists do not know exactly why, people with high cholesterol are more likely to have kidney problems. Keeping cholesterol under control — either through diet or medicine — seems to help preserve renal function.
Easy with the salt. Sodium in your diet may raise your blood pressure, so limit foods containing high levels of salt.
Take treatment. Make sure you take your HIV meds every day so as to keep the virus under control, and keep all of your medical appointments.