Your kidneys are bean-shaped organs that perform many important functions.
They’re in charge of filtering blood, removing waste through urine, producing hormones, balancing minerals and maintaining fluid balance.
There are many risk factors for kidney disease. The most common are uncontrolled diabetes and high blood pressure.
Alcoholism, heart disease, hepatitis C virus and HIV infection are also causes ().
When the kidneys become damaged and are unable to function properly, fluid can build up in the body and waste can accumulate in the blood.
However, avoiding or limiting certain foods in your diet may help decrease the accumulation of waste products in the blood, improve kidney function and prevent further damage ().
Dietary restrictions vary depending on the stage of kidney disease.
For instance, people who are in the early stages of chronic kidney disease will have different dietary restrictions than those with end-stage renal disease, or kidney failure.
Those with end-stage renal disease who require dialysis will also have varying dietary restrictions. Dialysis is a type of treatment that removes extra water and filters waste.
The majority of those in the late stages or with end-stage kidney disease will need to follow a kidney-friendly diet to avoid build-up of certain chemicals or nutrients in the blood.
In those with chronic kidney disease, the kidneys cannot adequately remove excess sodium, potassium and phosphorus. As a result, they are at higher risk of elevated blood levels of these minerals.
A kidney-friendly diet, or a “renal diet,” usually includes limiting sodium and potassium to 2,000 mg per day and limiting phosphorus to 1,000 mg per day.
Damaged kidneys may also have trouble filtering the waste products of protein metabolism. Therefore, individuals with chronic kidney disease in stages 1–4 may need to limit the amount of protein in their diets ().
However, those with end-stage renal disease undergoing dialysis have an increased protein requirement ().
Here are 17 foods that you should likely avoid on a renal diet.
In addition to the calories and sugar that colas provide, they also contain additives that contain phosphorus, especially dark-colored colas.
Many food manufacturers add phosphorus during the processing of food and beverages to enhance flavor, prolong shelf life and prevent discoloration.
This added phosphorus is much more absorbable by the human body than natural, animal- or plant-based phosphorus ().
Unlike natural phosphorus, phosphorus in the form of additives is not bound to protein. Rather, it’s found in the form of salt and highly absorbable by the intestinal tract ().
Additive phosphorus can typically be found in a product’s ingredient list. However, food manufacturers are not required to list the exact amount of additive phosphorus on the food label.
While additive phosphorus content varies depending on the type of cola, most dark-colored colas are believed to contain 50–100 mg in a 200-ml serving ().
As a result, colas, especially those dark in color, should be avoided on a renal diet.
Summary Dark-colored colas should be avoided on a renal diet because they contain phosphorus in its additive form, which is highly absorbable by the human body.
Avocados are often touted for their many nutritious qualities, including their heart-healthy fats, fiber and antioxidants.
While avocados are usually a healthy addition to the diet, individuals with kidney disease may need to avoid them.
This is because avocados are a very rich source of potassium. One cup (150 grams) of avocado provides a whopping 727 mg of potassium (8).
That’s double the amount of potassium than a medium banana provides.
Therefore, avocados, including guacamole, should be avoided on a renal diet, especially if you have been told to watch your potassium intake.
Summary Avocados should be avoided on a renal diet due to their high potassium content. One cup of avocado provides nearly 37% of the 2,000 mg potassium restriction.
Canned foods, such as soups, vegetables and beans, are often purchased because of their low cost and convenience.
However, most canned foods contain high amounts of sodium, as salt is added as a preservative to increase its shelf life ().
Because of the amount of sodium found in canned goods, it’s often recommended that people with kidney disease avoid or limit their consumption.
Choosing lower-sodium varieties or those labeled “no salt added” is typically best.
Additionally, draining and rinsing canned foods, such as canned beans and tuna, can decrease the sodium content by 33–80%, depending on the product ().
Summary Canned foods are often high in sodium. Avoiding, limiting or buying low-sodium varieties is likely best to reduce your overall sodium consumption.
Choosing the right bread can be confusing for individuals with kidney disease.
Often for healthy individuals, whole-wheat bread is usually recommended over refined, white flour bread.
Whole-wheat bread may be a more nutritious choice, mostly due to its higher fiber content. However, white bread is usually recommended over whole-wheat varieties for individuals with kidney disease.
This is because of its phosphorus and potassium content. The more bran and whole grains in the bread, the higher the phosphorus and potassium contents.
For example, a 1-ounce (30-gram) serving of whole-wheat bread contains about 57 mg of phosphorus and 69 mg of potassium. In comparison, white bread contains only 28 mg of both phosphorus and potassium (11, 12).
Note that most bread and bread products, regardless of being white or whole wheat, also contain relatively high amounts of sodium ().
It’s best to compare nutrition labels of various types of bread, choose a lower-sodium option, if possible, and monitor your portion sizes.
Summary White bread is typically recommended over whole-wheat bread on a renal diet due to its lower phosphorus and potassium levels. All bread contains sodium, so it’s best to compare food labels and choose a lower-sodium variety.
Like whole-wheat bread, brown rice is a whole grain that has a higher potassium and phosphorus content than its white rice counterpart.
You may be able to fit brown rice into a renal diet, but only if the portion is controlled and balanced with other foods to avoid excessive daily intake of potassium and phosphorus.
Bulgur, buckwheat, pearled barley and couscous are nutritious, lower-phosphorus grains that can make a good substitute for brown rice.
Summary Brown rice has a high content of phosphorus and potassium and will likely need to be portion-controlled or limited on a renal diet. White rice, bulgur, buckwheat and couscous are all good alternatives.
Bananas are known for their high potassium content.
While they’re naturally low in sodium, one medium banana provides 422 mg of potassium (16).
It may be difficult to keep your daily potassium intake to 2,000 mg if a banana is a daily staple.
Unfortunately, many other tropical fruits have high potassium contents as well.
However, pineapples contain substantially less potassium than other tropical fruits and can be a more suitable, yet tasty, alternative (17).
Summary Bananas are a rich source of potassium and may need to be limited on a renal diet. Pineapple is a kidney-friendly fruit, as it contains much less potassium than certain other tropical fruits.
Dairy products are rich in various vitamins and nutrients.
They’re also a natural source of phosphorus and potassium and a good source of protein.
For example, 1 cup (8 fluid ounces) of whole milk provides 222 mg of phosphorus and 349 mg of potassium (18).
Yet, consuming too much dairy, in conjunction with other phosphorus-rich foods, can be detrimental to bone health in those with kidney disease.
This may sound surprising, as milk and dairy are often recommended for strong bones and muscle health.
However, when the kidneys are damaged, too much phosphorus consumption can cause a buildup of phosphorus in the blood. This can make your bones thin and weak over time and increase the risk of bone breakage or fracture ().
Dairy products are also high in protein. One cup (8 fluid ounces) of whole milk provides about 8 grams of protein (18).
It may be important to limit dairy intake to avoid the buildup of protein waste in the blood.
Dairy alternatives like unenriched rice milk and almond milk are much lower in potassium, phosphorus and protein than cow’s milk, making them a good substitute for milk while on a renal diet.
Summary Dairy products contain high amounts of phosphorus, potassium and protein and should be limited on a renal diet. Despite milk’s high calcium content, its phosphorus content may weaken bones in those with kidney disease.
While oranges and orange juice are arguably most well known for their vitamin C contents, they are also rich sources of potassium.
Given their potassium content, oranges and orange juice likely need to be avoided or limited on a renal diet.
Grapes, apples and cranberries, as well as their respective juices, are all good substitutes for oranges and orange juice, as they have lower potassium contents.
Summary Oranges and orange juice are high in potassium and should be limited on a renal diet. Try grapes, apples, cranberries or their juices instead.
Processed meats have long been associated with chronic diseases and are generally considered unhealthy due to their content of preservatives (, , , ).
Processed meats are meats that have been salted, dried, cured or canned.
Some examples include hot dogs, bacon, pepperoni, jerky and sausage.
Processed meats typically contain large amounts of salt, mostly to improve taste and preserve flavor.
Therefore, it may be difficult to keep your daily sodium intake to less than 2,000 mg if processed meats are abundant in your diet.
Additionally, processed meats are high in protein.
If you have been told to monitor your protein intake, it’s important to limit processed meats for this reason as well.
Summary Processed meats are high in salt and protein and should be consumed in moderation on a renal diet.
Pickles, processed olives and relish are all examples of cured or pickled foods.
Usually, large amounts of salt are added during the curing or pickling process.
Processed olives also tend to be salty because they are cured and fermented to taste less bitter. Five green pickled olives provide about 195 mg of sodium, which is a significant portion of the daily amount in only a small serving (28).
Many grocery stores stock reduced-sodium varieties of pickles, olives and relish, which contain less sodium than the traditional varieties.
However, even reduced-sodium options can still be high in sodium, so you will still want to watch your portions.
Summary Pickles, processed olives and relish are high in sodium and should be limited on a renal diet.
Apricots are rich in vitamin C, vitamin A and fiber.
They are also high in potassium. One cup of fresh apricots provides 427 mg of potassium (29).
Furthermore, the potassium content is even more concentrated in dried apricots.
One cup of dried apricots provides over 1,500 mg of potassium (30).
This means that just one cup of dried apricots provides 75% of the 2,000 mg low-potassium restriction.
It’s best to avoid apricots, and most importantly dried apricots, on a renal diet.
Summary Apricots are a high-potassium food that should be avoided on a renal diet. They offer over 400 mg per 1 cup raw and over 1,500 mg per 1 cup dried.
Potatoes and sweet potatoes are potassium-rich vegetables.
Fortunately, some high-potassium foods, including potatoes and sweet potatoes, can be soaked or leached to reduce their potassium contents.
Cutting potatoes into small, thin pieces and boiling them for at least 10 minutes can reduce the potassium content by about 50% ().
Potatoes that are soaked in a large pot of water for at least four hours before cooking are proven to have an even lower potassium content than those not soaked before cooking ().
This method is known as “potassium leaching,” or the “double cook method.”
Although double cooking potatoes lowers the potassium content, it’s important to remember that their potassium content isn’t completed eliminated by this method.
Considerable amounts of potassium can still be present in double-cooked potatoes, so it’s best to practice portion control to keep potassium levels in check.
Summary Potatoes and sweet potatoes are high-potassium vegetables. Boiling or double cooking potatoes can decrease potassium by about 50%.
Tomatoes are another high-potassium fruit that may not fit the guidelines of a renal diet.
They can be served raw or stewed and are often used to make sauces.
Just one cup of tomato sauce can contain upwards of 900 mg of potassium (35).
Unfortunately for those on a renal diet, tomatoes are commonly used in many dishes.
Choosing an alternative with lower potassium content depends largely on taste preference. However, swapping tomato sauce for a roasted red pepper sauce can be equally delicious, all while providing less potassium per serving.
Summary Tomatoes are another high-potassium fruit that should likely be limited on a renal diet.
Processed foods can be a major component of sodium in the diet.
Among these foods, packaged, instant and pre-made meals are usually the most heavily processed and thus contain the most sodium.
Examples include frozen pizza, microwaveable meals and instant noodles.
Keeping sodium intake to 2,000 mg per day may be difficult if you are eating highly processed foods on a regular basis.
Not only do heavily processed foods contain a large amount of sodium, they are commonly lacking in nutrients as well ().
Summary Packaged, instant and pre-made meals are highly processed items that can contain very large amounts of sodium and lack nutrients. It’s best to limit these foods on a renal diet.
Swiss chard, spinach and beet greens are leafy green vegetables that contain high amounts of various nutrients and minerals, including potassium.
While leafy vegetables shrink to a smaller serving size when cooked, the potassium content remains the same.
For example, a half cup of raw spinach will shrink to about 1 tablespoon when cooked. Thus, eating a half cup of cooked spinach will contain a much higher amount of potassium than a half cup of raw spinach.
Moderate consumption of raw Swiss chard, spinach and beet greens is preferable to cooked greens to avoid too much potassium.
Summary Leafy green vegetables like Swiss chard, spinach and beet greens are full of potassium, especially when served cooked. Although serving size becomes smaller when cooked, potassium content remains the same.
Dates, raisins and prunes are common dried fruits.
When fruits are dried, all of their nutrients are concentrated, including potassium.
Moreover, just four dates provide 668 mg of potassium (42).
Given the remarkable amount of potassium found in these common dried fruits, it’s best to go without while on a renal diet to ensure potassium levels remain favorable.
Summary Nutrients are concentrated when fruits are dried. Therefore, the potassium content of dried fruit, including dates, prunes and raisins, is extremely high and should be avoided on a renal diet.
Ready-to-eat snack foods like pretzels, chips and crackers tend to be lacking in nutrients and relatively high in salt.
Also, it’s easy to eat more than the recommended portion size of these foods, often leading to even greater salt intake than intended.
What’s more, if chips are made from potatoes, they will contain a significant amount of potassium as well.
Summary Pretzels, chips and crackers are easily consumed in large portions and tend to contain high amounts of salt. Additionally, chips made from potatoes provide a considerable amount of potassium.
If you have kidney disease, reducing your potassium, phosphorus and sodium intake can be an important aspect of managing the disease.
The high-sodium, high-potassium and high-phosphorus foods listed above are likely best limited or avoided.
Dietary restrictions and nutrient intake recommendations will vary based on the severity of your kidney damage.
Following a renal diet can seem daunting and a bit restrictive at times. However, working with your healthcare provider and a renal dietitian can help you design a renal diet specific to your individual needs.