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 (1).
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 (2). Diet and kidney disease
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 with late- or end-stage kidney disease will need to follow a kidney-friendly diet to avoid the buildup of certain chemicals or nutrients in the blood.
In those with chronic kidney disease, the kidneys cannot adequately remove excess sodium, potassium, or phosphorus. As a result, they’re at higher risk of elevated blood levels of these minerals.
A kidney-friendly diet, or renal diet, usually involves limiting sodium and potassium to 2,000 mg per day and limiting phosphorus to 800–1,000 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 (3).
However, those with end-stage renal disease undergoing dialysis have an increased protein requirement (4).
Here are 17 foods that you should likely avoid on a renal diet. 1. Dark-colored soda
In addition to the calories and sugar that sodas provide, they harbor additives that contain phosphorus, especially dark-colored sodas.
Many food and beverage manufacturers add phosphorus during processing to enhance flavor, prolong shelf life, and prevent discoloration.
Your body absorbs this added phosphorus to a greater extent than natural, animal-, or plant-based phosphorus (5).
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 (6).
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 soda, most dark-colored sodas are believed to contain 50–100 mg in a 200-mL serving (7).
As a result, sodas, especially those that are dark, should be avoided on a renal diet. 2. Avocados
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. 3. Canned foods
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 (9).
Due to 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 (10). 4. Whole wheat bread
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 whether they’re white or whole wheat, also contain relatively high amounts of sodium (13).
It’s best to compare the nutrition labels of various types of bread, choose a lower sodium option, if possible, and monitor your portion sizes. 5. Brown rice
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 an 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. 6. Bananas
Bananas are known for their high potassium content.
While they’re naturally low in sodium, 1 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). 7. Dairy
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 (240 mL) 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, which can pull calcium from your bones. This can make bones thin and weak over time and increase the risk of bone breakage or fracture (19).
Dairy products are also high in protein. One cup (240 mL) 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. 8. Oranges and orange juice
While oranges and orange juice are arguably most well known for their vitamin C contents, they’re 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. 9. Processed meats
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. 10. Pickles, olives, and relish
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, as they’re 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. 11. Apricots
Apricots are rich in vitamin C, vitamin A, and fiber.
They’re 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 1 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. 12. Potatoes and sweet potatoes
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% (33).
Potatoes that are soaked in water for at least 4 hours before cooking are proven to have an even lower potassium content than those not soaked before cooking (34).
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 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. 13. Tomatoes
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 1 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 and provide less potassium per serving. 14. Packaged, instant, and premade meals
Processed foods can be a major component of sodium in the diet.
Among these foods, packaged, instant, and premade 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’re eating highly processed foods regularly.
Heavily processed foods not only contain a large amount of sodium but also commonly lack nutrients (36). 15. Swiss chard, spinach, and beet greens
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, one-half cup of raw spinach will shrink to about 1 tablespoon when cooked. Thus, eating one-half cup of cooked spinach will contain a much higher amount of potassium than one-half cup of raw spinach.
Raw Swiss chard, spinach, and beet greens are preferable to cooked greens to avoid too much potassium.
However, moderate your intake of these foods, as they’re also high in oxalates which, for sensitive individuals, increases the risk of kidney stones. Kidney stones may further damage renal tissue and decrease kidney function. 16. Dates, raisins, and prunes
Dates, raisins, and prunes are common dried fruits.
When fruits are dried, all of their nutrients are concentrated, including potassium.
Moreover, just 4 dates provide 668 mg of potassium (42).
Given the high amount of potassium in these common dried fruits, it’s best to go without them while on a renal diet to ensure your potassium levels remain favorable. 17. Pretzels, chips, and crackers
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’ll contain a significant amount of potassium as well. The bottom line
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.