Currently no specific diet has been proven to make your polycystic kidneys better or keep them from getting worse. It is, however, ideal to eat a balanced and healthy diet to maintain optimal body conditions. A healthy body is able to fight infection better, and bounce back faster. Accumulation of waste products filtered by your kidneys will build up in your blood as kidney function declines. At the more advanced stages of kidney failure (i.e. GFR <30-40 percent), significant accumulation of these waste products in your blood can cause symptoms of kidney failure.
Should I stop eating protein?
The major source of these waste products is the food you eat, especially protein. Therefore, when you have lost a significant amount of kidney function, a lower protein diet may be ordered by your doctor.
Studies from both animals and humans with chronic kidney failure have shown that eating large amounts of protein may accelerate the progressive decline of kidney function. However, the Modification in Diet in Renal Disease (MDRD) study done by the National Institutes of Health (NIH) looked at protein intake and kidney function. The results did not show any benefit of lowering protein intake in individuals with PKD. At this time, there is no convincing evidence to suggest protein restriction as beneficial unless you are in kidney failure. Despite all of this, many consider it unwise to consume a very high protein diet. If you have moderate to advanced kidney failure, however, a modest restriction may be appropriate. For more information, you should consult your doctor and a dietitian experienced with kidney disease and ideally knowledge of PKD (also known as a renal dietician).
Should I stop eating salt?
High blood pressure in PKD does not seem to be caused by salt intake. Regardless, excessive amounts of salt should be avoided and lowering dietary salt may help in blood pressure control. This becomes important when people are on certain types of blood pressure medicine and when they have kidney failure.
Can I drink alcohol?
Light and/or occasional use of alcohol has not been shown to damage the kidneys or the liver. However, drinking three or more ounces of alcohol a day for many years has been associated with increases in blood pressure and can damage the liver.
Can I use tobacco?
Smoking increases the risk of heart disease and stroke and when paired with hypertension, the risks are even greater. Smoking also increases the risk of cancer.
Should I take extra vitamins to make sure I’m getting all the nutrients I need?
If you are maintaining a balanced and healthy diet, you typically will not need extra vitamins. Unlike food, vitamins are needed only in tiny amounts. Excess amounts of vitamin A, D and E can accumulate in your body and cause medical problems. Generally, if you feel you need extra vitamins, a one-a-day generic brand of vitamin is sufficient. Consult your doctor before taking extra vitamins of any kind. Because there is an increased incidence of calcium kidney stones in individuals with PKD, women with PKD should discuss with their doctor the proper amount of calcium needed. Limiting calcium in the diet will not prevent kidney stones in non-PKD patients and the beneficial effects of dairy product intake on skeletal and cardiovascular systems are well established.
How much fluid should I drink each day?
A chemical called cyclic AMP (cAMP) has been shown to promote growth of polycystic kidneys. In your kidney, cAMP is produced in response to a hormone, vasopressin, which is produced by the brain in response to not having enough water. Thus avoiding dehydration is thought to be prudent. In addition, generous water intake has the potential to suppress vasopressin production and decrease cAMP production in the kidney. Though there is no good data regarding this in humans with PKD, if kidney function is not impaired, water intake is typically safe. Therefore it seems reasonable to suggest intake of water with a goal of 2-3 quarts of urine output daily. Your urine should generally be pale in color. This will tend to suppress vasopressin production by the brain and cAMP production in the kidneys. In addition, it is generally suggested that PKD patients limit caffeine intake, since caffeine slows degradation of cAMP. Finally, generous water intake helps maintain a dilute urine and decreases the risk of kidney stones, which are seen at increased frequency in PKD patients.
It is important to understand that the benefit or risk of high water intake have never been formally studied in PKD patients, and therefore results cannot be predicted or guaranteed. In addition, as kidney function deteriorates, generous water intake can be problematic and even dangerous. Thus, it is important to discuss appropriate water intake with your doctor.
Will caffeine damage my kidneys?
There is no direct evidence that caffeine will damage your polycystic kidneys. However, studies of PKD cells grown in a lab have shown that caffeine-like substances promoted cyst growth in PKD. At this time, it may be wise to limit caffeine intake to less than 200 to 250 mg (i.e. two to three cups of coffee) a day.
What about potassium?
Potassium is essential to all living cells and is important for muscle and nerve functions in the body. It is found in most foods including legumes, whole grains, fruits, green vegetables, potatoes, meats, milk and yogurt. Although potassium is vital to the body, it is not wise to take potassium supplements in pill or liquid form without consulting your doctor and/or your renal dietician, especially if your kidney function is reduced.
What about calcium and magnesium?
In non-PKD settings, a deficiency of calcium and magnesium has been associated with high blood pressure. Dietary calcium and magnesium are best provided by dairy products and are important in maintaining a normal mineral balance as part of healthy diet.
Essentials for a balanced and healthy diet
Given the current obesity epidemic that is prevalent in all developed countries, the following provides a simple conceptual framework for a balanced and healthy diet:
Tips for a healthy diet:
- High fiber: fresh vegetables and nuts
- Carbohydrates: minimize intake of bread and pasta
- Protein: moderation of red meats
- Fat: moderate intake may actually decrease hunger drive (Olive oil in salad dressing to increase fat intake)
- Avoid: processed food and sugary drinks with fructose syrup
- Decrease food portion size if you are overweight
If you have moderate to advanced kidney failure, further modification of the above will be required and consultation with your doctor and a dietitian experienced with kidney disease is recommended.
Studies in high blood pressure patients without PKD have shown that the so-called DASH diet (Dietary Approach to Stopping Hypertension), which consists of lots of fruits and vegetables combined with low-fat dairy, may lower blood pressure. A diet based on these guidelines could also seem appropriate for you. Look in the resources section at the back of the book for web resources on the DASH diet. Talk to your doctor before significantly altering your diet.