Editor’s Note: The term “kidney patients” in this article mainly refers to patients with chronic kidney disease (CKD) and those on dialysis. Special populations, including patients with acute kidney injury, kidney transplant recipients, children, and pregnant women, should strictly follow the individualized advice of their attending physicians and should not directly apply the recommendations in this article.

The kidneys are vital organs for metabolism and excretion. Once kidney function is impaired, dietary management becomes especially important. For kidney patients, eating the wrong foods may not only increase the burden on the kidneys, but may also lead to edema, hyperkalemia, hyperphosphatemia, and other complications. Therefore, extra caution is needed in daily diet to avoid several categories of high-risk foods.

1. Strictly control high-salt foods

Pickled vegetables, cured meats, salted fish, ham, instant noodles, and other preserved or pickled products are all high-salt foods. Excessive salt intake can easily cause sodium and water retention, raise blood pressure, increase the burden on the kidneys, and may also trigger edema.

Kidney patients should keep their diet light. It is generally recommended to limit total daily salt intake to within 5 grams. Patients with severe edema or hypertension should strictly limit intake to within 3 grams per day under the guidance of a doctor or dietitian. Note that salt-free or low-sodium diets are mostly used under strict inpatient or nutrition clinic management; long-term self-administration at home may lead to hyponatremia, fatigue, and poor appetite, so do not attempt them on your own.

At the same time, use less soy sauce, bean paste, monosodium glutamate, chicken bouillon, oyster sauce, fermented bean curd, and other high-sodium condiments—these “hidden sodium” sources can also raise blood pressure and increase kidney burden. During cooking, natural flavorings such as green onion, ginger, garlic, lemon juice, Sichuan peppercorn, and star anise may be used instead. In addition, hidden sodium in processed foods such as dried noodles, bread, salty snacks, and instant soup mixes should also be counted toward the daily total.

Reminder: Low-sodium salts often replace part of the sodium chloride with potassium chloride, which may not be suitable for patients at risk of hyperkalemia.

2. High-potassium foods should be judged based on kidney function and blood potassium levels

Bananas, oranges, potatoes, spinach, mushrooms, kelp, and similar foods are relatively high in potassium. Other high-potassium foods include dried mushrooms, dried dates, coconut water, avocado, sweet potato, and dried legumes, which also require attention. Most fresh tomatoes are low to moderate in potassium; individuals with high potassium should still control portion size. Patients with normal blood potassium or early-stage kidney disease may consume small amounts. Blanching or soaking before cooking can reduce some potassium content. However, concentrated products such as tomato paste and tomato juice are relatively high in potassium and should be avoided by those at high risk of hyperkalemia.

Whether potassium restriction is necessary cannot be generalized. Reference may be made to the Dietary Guidance for Adult Chronic Kidney Disease (2024 Edition):

CKD stages 1–2, with normal blood potassium, normal urine output, and no use of potassium-sparing medications: strict potassium restriction is usually unnecessary. Vegetable intake of 300–500 g/day and fruit intake of 200–350 g/day may be followed according to guidelines (100–200 g/day for diabetic kidney disease). Premature or excessive potassium restriction may instead lead to nutritional imbalance.

CKD stage 3a: potassium intake may basically remain unrestricted, following the above principles.

CKD stage 3b, or patients with a history of hyperkalemia, oliguria, or use of potassium-sparing drugs: individualized potassium restriction should begin; it is not necessary to wait until stages 4–5.

CKD stages 4–5, patients on dialysis, or those with recurrent hyperkalemia: high-potassium foods should be strictly limited.

Any stage with hyperkalemia: timely intervention is required; potassium restriction does not necessarily have to wait until stages 4–5.

Potassium-reduction cooking tips: Blanch vegetables before cooking to reduce some potassium. For root vegetables such as potatoes and Chinese yam, slicing followed by soaking for more than 30 minutes and then blanching improves potassium removal. However, soaking time should not be excessively long, to avoid substantial loss of water-soluble vitamins. Additional hidden high-potassium sources requiring caution include low-sodium salt, canned tomatoes, vegetable juices, sports drinks, and yeast powder.

⚠️ At any stage of hyperkalemia, self-administered “dietary supplementation” or “pharmaceutical supplementation” with high-potassium foods or potassium supplements is strictly prohibited. All medication adjustments and treatments must be carried out under medical supervision.

3. Choose high-phosphorus foods cautiously, and distinguish natural phosphorus from additive phosphorus

Phosphorus in plant-based foods mostly exists in the form of phytate. Because humans lack phytase, its bioavailability is usually low (about 10%–30%, generally below 50%). Organic phosphorus in animal-based foods such as meat, fish, eggs, and dairy has a bioavailability of about 40%–60% (some consensus statements give an overall range of 35%–86% for organic phosphorus). In contrast, phosphorus additives (inorganic phosphorus) in processed foods have a bioavailability as high as 90%–100%.

Therefore, although plant-based foods such as nuts and legumes contain phosphorus with relatively low bioavailability, this does not mean that patients with high blood phosphorus may eat them freely. Patients at CKD stages 3–5, those on dialysis, or those with hyperphosphatemia should still limit intake and include these foods in total daily phosphorus management; patients with hyperphosphatemia or on dialysis should be especially cautious. It should be emphasized that low absorption of natural plant phosphorus does not mean that patients with high phosphorus or on dialysis may eat freely; moderate absorption of natural animal phosphorus does not mean it is always safer than additives. The key factors are total phosphorus intake, the protein-to-phosphorus ratio, and whether additives are present. Naturally high-phosphorus animal foods such as organ meats and egg yolks should also be consumed in moderation. Patients with high blood phosphorus may reduce egg yolk intake while retaining egg white. When cooking, boiling meat and discarding the cooking water before further preparation may help reduce some water-soluble phosphorus and potassium. However, boiling meat and discarding the broth has limited effect on removing organic phosphorus from protein and cannot replace total phosphorus restriction or phosphate binder therapy.

What truly requires high alertness is phosphorus additives in deeply processed foods such as processed meat products, carbonated beverages, instant snacks, non-dairy creamer, and instant soup mixes. This type of inorganic phosphorus has extremely high bioavailability and is highly unfavorable for blood phosphorus control. When purchasing packaged foods, always check the ingredient list, and be especially cautious of additives containing the word “phosphate,” such as disodium hydrogen phosphate, sodium tripolyphosphate, sodium pyrophosphate, sodium hexametaphosphate, and calcium dihydrogen phosphate.

Phosphorus restriction targets for reference: Non-dialysis CKD stage 3–5 patients are generally advised to limit daily phosphorus intake to 800–1,000 mg. For dialysis patients, individualized targets should be developed by the nutrition department based on blood phosphorus levels and protein needs. Do not blindly restrict all patients to below 800 mg per day, as this may lead to malnutrition.

4. High-purine foods should not be consumed excessively (especially for patients with hyperuricemia/gout)

Seafood (especially shellfish and sardines), animal organ meats, concentrated meat broths, and hot pot broth are relatively high in purines and may easily trigger hyperuricemia and gout. Beer and yellow rice wine themselves contain relatively high levels of purines, and alcohol in all alcoholic beverages, including baijiu, inhibits uric acid excretion. Beer and yellow rice wine also add an additional purine load.

Patients with hyperuricemia, gout, or CKD stages 3–5 should avoid alcohol, and other kidney patients should strictly limit alcohol intake. Hyperuricemia is closely related to CKD progression, so patients with hyperuricemia, gout, or uric acid stones should重点 reduce intake of these foods and avoid long-simmered meat broths and hot pot broth. For kidney patients without gout or uric acid stones, high-quality protein sources such as fish and poultry do not need to be completely avoided; varieties with relatively lower purine content may be chosen in moderation. Although ordinary kidney patients do not need extreme dietary restrictions, they should drink fewer concentrated broths and limit alcohol, avoiding excessive avoidance of meat that could lead to insufficient high-quality protein intake. Note that during acute gout attacks, restriction of the above high-purine foods should be stricter than during chronic hyperuricemia, to avoid disease recurrence.

5. Protein intake should be moderate and of high quality

During the acute phase or when kidney function declines significantly, total daily protein intake should be controlled under the guidance of a doctor or dietitian. The following protein intake recommendations are based on ideal body weight or a weight selected by the physician and apply to non-dialysis patients with stable conditions. They should not be mechanically applied to patients with malnutrition, older adults, those with sarcopenia, acute illness, or significant proteinuria; individualized plans should be developed by nephrology or nutrition specialists.

When protein intake needs to be restricted, high-quality protein—such as fish, lean meat, eggs, dairy products, and soy products—should account for more than 50% of total protein.

Soy protein is a high-quality plant protein. Moderate intake by patients with kidney insufficiency will not increase kidney burden, and it may appropriately replace part of animal protein; complete avoidance is unnecessary. However, because soy milk contains a relatively high amount of water, it should be counted toward daily fluid intake, and patients with kidney insufficiency should consume it in moderation. If strict fluid restriction is required, soy products with lower water content, such as tofu and dried tofu strips, may replace part of animal protein.

⚠️ Specific protein intake must follow medical advice and be individually adjusted according to body weight, kidney function indicators, and dialysis modality.

6. Other considerations

Cooking methods: Use low-oil cooking methods such as steaming, boiling, and stewing to reduce fat intake. Daily cooking oil should be limited to 25–40 g, and fat should contribute no more than 35% of total energy intake.

Individualization principle: Dietary restrictions vary considerably depending on the type and stage of kidney disease. This article provides general advice. Specific dietary plans must be individualized based on CKD stage, dialysis modality, and laboratory results, in consultation with a doctor or registered dietitian. Do not adopt extreme self-imposed dietary restrictions.

This article is for educational reference only and does not replace professional medical advice. Blood potassium, blood phosphorus, urine output, body weight, medication use, and kidney function indicators change dynamically. Dietary restrictions should not be based solely on “food lists,” but must also consider recent laboratory results. Seek medical attention promptly if symptoms such as fatigue, palpitations, numbness in the limbs, markedly reduced urine output, or worsening edema occur.