The kidneys filter waste products from the blood and send them out of the body in the urine. They are also responsible for balancing fluid and electrolyte levels.
The kidneys perform these tasks with no outside help. Several conditions, such as diabetes and high blood pressure, may affect their ability to function.
Ultimately, damage to the kidneys may lead to chronic kidney disease (CKD). As the authors of a 2016 article note, diet is the most significant risk factor for CKD-related death and disability, making dietary changes a key part of treatment.
Following a kidney-healthy diet plan may help the kidneys function properly and prevent damage to these organs. However, although some foods generally help support a healthy kidney, not all of them are suitable for people who have kidney disease.
The kidneys use water to filter toxins out of the body.
Water is the most important drink for the body. The cells use water to transport toxins into the bloodstream.
The kidneys then use water to filter these toxins out and to create the urine that transports them out of the body.
A person can support these functions by drinking whenever they feel thirsty.
Salmon, tuna, and other cold-water, fatty fish that are high in omega-3 fatty acids can make a beneficial addition to any diet.
The body cannot make omega-3 fatty acids, which means that they have to come from the diet. Fatty fish are a great natural source of these healthful fats.
As the National Kidney Foundation note, omega-3 fats may reduce fat levels in the blood and also slightly lower blood pressure. As high blood pressure is a risk factor for kidney disease, finding natural ways to lower it may help protect the kidneys.
Sweet potatoes are similar to white potatoes, but their excess fiber may cause them to break down more slowly, resulting in less of a spike in insulin levels. Sweet potatoes also contain vitamins and minerals, such as potassium, that may help balance the levels of sodium in the body and reduce its effect on the kidneys.
However, as sweet potato is a high-potassium food, anyone who has CKD or is on dialysis may wish to limit their intake of this vegetable.
Dark leafy greens
Dark leafy greens, such as spinach, kale, and chard, are dietary staples that contain a wide variety of vitamins, fibers, and minerals. Many also contain protective compounds, such as antioxidants.
However, these foods also tend to be high in potassium, so they may not be suitable for people on a restricted diet or those on dialysis.
Dark berries, which include strawberries, blueberries, and raspberries, are a great source of many helpful nutrients and antioxidant compounds. These may help protect the cells in the body from damage.
Berries are likely to be a better option than other sugary foods for satisfying a sweet craving.
An apple is a healthful snack that contains an important fiber called pectin. Pectin may help reduce some risk factors for kidney damage, such as high blood sugar and cholesterol levels.
Apples can also often satisfy a sweet tooth.
Foods to avoid
There are several foods that people should avoid if they want to improve their kidney health or prevent damage to these organs.
These include the following:
Too much phosphorus can put stress on the kidneys. Research has shown that there is a correlation between high phosphorous intake and an increased risk of long-term damage to the kidneys.
However, there is not enough evidence to prove that phosphorous causes this damage, so more research into this topic is necessary.
For people looking to reduce their phosphorous intake, foods high in phosphorous include:
- dairy products
- most grains
Some types of protein may be harder for the kidneys, or the body in general, to process. These include red meat.
Initial research has shown that people who eat a lot of red meat have a higher risk of end-stage kidney disease than those who eat less red meat. However, there is a need for more studies to investigate this risk.
Foods for people with CKD
Cabbage may be beneficial for people with CKD.
While the above foods may support a healthy kidney in general, they are not usually the best choices for people with CKD.
Doctors will put most people with CKD on a specific diet to avoid minerals that the kidneys process, such as sodium, potassium, and phosphorous.
The National Institute of Diabetes and Digestive and Kidney Diseases recommend that people with CKD eat less than 2,300 milligrams of sodium each day.
As CKD progresses, people may also need to limit their phosphorous intake, as this mineral can build up in the blood of people with this disease.
Choosing the right amount of potassium is also important for people with CKD, as problems may occur when potassium levels get too high or low.
People with CKD should aim to eat healthful foods that are low in these minerals but still provide the body with other nutrients.
It may also be important for people with CKD to reduce their protein intake and only include small amounts of protein in their meals. When the body uses protein, it turns into waste, which the kidneys must then filter out.
As a 2017 study notes, eating a diet lower in protein may protect against complications of CKD, such as metabolic acidosis, which occurs as kidney function deteriorates. The researchers indicated that eating a diet rich in fruits and vegetables and low in protein might help reduce these risks.
People with CKD can work directly with a dietitian to create a suitable diet plan that meets their needs.
Cabbage is a leafy vegetable that may be beneficial for people with CKD. It is relatively low in potassium and very low in sodium, yet it also contains many helpful compounds and vitamins.
Red bell peppers
In addition to being very low in minerals such as sodium and potassium, red bell peppers contain helpful antioxidant compounds, which may protect the cells from damage.
Garlic is an excellent seasoning choice for people with CKD. It can give other foods a more satisfying, full flavor, which may reduce the need for extra salt. Garlic also offers a range of health benefits.
Cauliflower is a versatile vegetable for people with CKD. With the right preparation, it makes a good replacement for foods such as rice, mashed potatoes, and even pizza crust.
Cauliflower also contains a range of nutrients without providing too much sodium, potassium, or phosphorous.
People with CKD may have to avoid many greens, but arugula can be a great replacement. Arugula is generally lower in potassium than other greens, but it still contains fiber and other beneficial nutrients.
Blueberries are a healthful snack for people with CKD.
The fruits below can be a healthful sweet snack for people with CKD:
- red grapes
Olive oil may be the best cooking oil because of the type of fat that it contains. Olive oil is high in oleic acid, which is a polyunsaturated fatty acid that may help reduce inflammation in the body.
Eggs are a simple protein, but the yolks are very high in phosphorous. People with CKD can make omelets or scrambled eggs using just the egg whites.
Foods for people with CKD to avoid
For people with CKD, some foods may be difficult for the body to process and might place more stress on the kidney. These include:
- white potatoes
- red meat
- dairy products
- sugary beverages
- canned foods
- pickled foods
- egg yolks
People looking to protect their kidneys from future damage may also want to consider eating these foods in moderation.
The kidneys play an important role in filtering the blood and eliminating waste products in the urine. Many foods may help support an already healthy kidney and prevent damage to this organ.
However, people with chronic kidney disease will need to follow a different set of dietary rules to protect their kidneys from further damage.
It is always best to talk to a licensed dietitian before moving forward with any dietary changes.