How effective are diet and exercise?
Diet recommendations vary according to the stage of chronic kidney disease. If you pay attention to what you eat and drink, and get enough exercise too, you can have a positive impact on the course of the disease and improve your wellbeing.
A lot of metabolic processes depend on the performance of the kidneys: If your kidneys stop working properly, it causes an imbalance in your energy and protein metabolism, for instance. The levels of salts and fluids in the body are also affected. Advanced kidney disease may then cause serious complications such as weight loss, acidosis (a build-up of acid), and fluid retention in organs and tissue.
So people who have chronic kidney disease are advised to follow a number of dietary recommendations. It’s often quite difficult to stick to this special "kidney-friendly" diet. But doctors and dietitians can help you to understand the recommendations and put them into practice. People who have chronic kidney disease often get used to these recommendations over time and use them as an opportunity to do something good for their wellbeing. Changes to your diet and exercise also have a positive effect on other medical conditions and risk factors, such as high blood pressure.
How much can you drink?
Most people who have chronic kidney disease can drink as much as they like at first. If the performance of the kidneys keeps getting worse, many people release less and less fluids. If you then also drink too much liquid, it can't leave your body fast enough. This results in edema (swelling due to fluid retention) and rising blood pressure levels. Dialysis can only compensate for this to a certain extent, because the amount of water it can remove from the body is limited.
Depending on the type of dialysis and whether the kidneys are still excreting urine (and how much), the following recommendations apply: Ideally, you should only drink as much fluids as the kidneys excrete in the form of urine – plus 0.5 liters per day in hemodialysis or 0.8 liters per day in peritoneal dialysis. This amount includes both drinks and liquid foods such as soups, yogurt and stewed fruit.
To make sure you don't drink too much, it can help to use smaller glasses and cups, and to take medication with a meal instead of with an extra glass of water, if possible. You can help suppress your thirst by chewing on a sour candy, a slice of lemon or sugar-free gum. Drinking slowly and avoiding dry indoor air can also help.
Maintaining a normal weight
But it is rare for people with advanced chronic kidney disease to be overweight – they are more likely to lose too much weight instead. To prevent being underweight, it is important to eat enough and to eat right. It is recommended that dialysis patients eat 30 to 40 kilocalories (kcal) per kilogram of normal weight. By “normal weight” we don't mean your current weight, but the weight that is considered to be normal for your height according to the body mass index (BMI) formula. This would be 70 kg for a man who is 180 cm tall, for example. Based on that normal weight, the recommended amount of calories would be 2,100 to 2,800 kilocalories per day.
How much protein does your body need?
People who do not yet need to have dialysis should be careful to get the right amount of protein – not too much, but also not too little. Several studies have shown that in some people, a low-protein diet can delay the progression of chronic kidney disease and prevent complications. There is not yet enough evidence to say whether other types of diets might also have these positive effects. But it's important to make sure that you don't get too little protein either, because our bodies start breaking down the protein in our muscles if we don't get enough protein in our diet.
According to current recommendations, people should get about 0.8 to 1 gram of protein in their daily diet for each kilogram of normal weight. So if you weigh about 70 kilograms, this would mean you would ideally get about 60 grams of protein in your diet. To give you an idea of how much that is: A single beef steak (140 grams) typically has about 45 grams of protein in it, a hard-boiled egg has about 13 grams in it, and an apple has less than 0.5 grams in it.
People who are on dialysis will need more protein, though. People who are on hemodialysis are advised to get at least 1.1 grams of protein in their daily diet per kilogram of (normal) body weight, and those who are on peritoneal dialysis should get up to 1.5 grams per day and kilo. The reason why more protein is needed for peritoneal dialysis is because a lot of protein is lost to the dialysis fluid through the peritoneum.
How much salt is allowed?
High blood pressure and too much protein in urine can make chronic kidney disease get worse faster. Studies have shown that a low-salt diet can reduce blood pressure as well as the loss of protein. Based on initial research, experts think that it can help delay or lower the risk of complications like kidney failure or heart attacks. But these results still need to be confirmed in long-term studies.
Salt also causes your body to "hold onto" too much fluid and makes you more thirsty. So if someone is on dialysis and they aren't allowed to drink a lot of liquids, it's especially important that they use salt sparingly.
About 5 to 6 grams of salt are recommended per day. As a basic guide, one slice of bread contains about 0.5 grams of salt, a hot dog sausage has about 2 grams in it and a slice of pizza has over 4 grams in it. Avoiding salty foods can be difficult, especially at first. But after two to three weeks, your sense of taste becomes used to less salt. Some dishes can be made tastier by using herbs, onions, lemon, vinegar or other spices instead.
In advanced kidney disease, it’s not only salt (sodium chloride) that is a problem. The kidneys also have trouble regulating the levels of potassium and especially phosphate. So dialysis patients should stop eating foods that contain a lot of these minerals as much as possible. These foods include potatoes, bananas, dried fruit, potato chips, French fries, processed cheese (spreads), milk and nuts. Low-sodium or sodium-free salt substitutes should be used with caution: They have low amounts of sodium, but contain a lot of potassium.
How much exercise is good for you?
Getting exercise is good for you, even if you have chronic kidney disease. Regular exercise can help to lower your blood pressure, maintain muscle tissue and help you to feel better overall.
Experts recommend 30 minutes of low-intensity sports five times a week. If you can’t do that, it’s still important to get as much exercise as possible. Scheduling physical activity as part of your everyday routine and having friends and family support you in your goals can help. It's even possible to exercise during a dialysis session – by pedaling on a specially designed bed exercise bike, for example.
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