How can eating protect the kidneys?

Patients with chronic kidney disease (CKD) face many challenges in nutritional balance.Uremia itself suppresses appetite and reduces nutrient intake.Dialysis treatment can also lead to the loss of a small amount of nutrients.There are other factors such as acidosis, insulin resistance, and chronic inflammation that promote protein breakdown.It is estimated that the cost of treating malnourished patients in hospitals is twice that of well-nourished patients.Therefore, nutritional therapy is an important part of CKD treatment. It can not only improve the symptoms of uremia and related complications, such as electrolyte acid-base imbalance, water-salt metabolism disorders, mineral and bone metabolism abnormalities, etc., but also slow down the rate of renal dysfunction.

The American Society for Parenteral and Enteral Nutrition (ASPEN) uses the following six evidence-based criteria for nutritional assessment：

• Insufficient energy intake
• Weight loss
• Muscle loss
• Loss of subcutaneous fat
• The functional state is weakened (measured by the grip of the hand)
• 
  

If a patient with CKD has two or more symptoms, it can be diagnosed as malnutrition

What is nutritional therapy?

Nutritional therapy is not a simple supplement to nutrition, but according to the characteristics of the disease, patients with chronic kidney disease are formulated with personalized dietary formulas to improve symptoms, delay the progress of CKD, and improve the quality of life.

Why do you need a low-protein diet?

The ability of the kidneys of patients with CKD to excrete metabolic waste is greatly reduced, so protein catabolic waste such as urea, creatinine, guanidine, etc. will accumulate in the blood and become uremic toxins.Reducing the protein of food, that is, a low-protein diet, can reduce the production and accumulation of protein cataboloids, thereby reducing the high-load working state of the damaged kidneys and delaying the progress of renal insufficiency.Therefore, a low-protein diet (0.6g/kg/day) is an important means of treatment for patients with chronic kidney disease.

What should I pay attention to when adhering to a low-protein diet for a long time?

1、Guaranteed energy intake

When restricting protein intake, if the energy intake is insufficient, the patient may develop protein-heat malnutrition, which affects the prognosis of the disease and increases the mortality rate; adequate energy intake can play a role in saving protein, ensuring that the ingested protein is effectively used to reduce urea nitrogen production.The "U.S. Clinical Practice Guidelines for Chronic Kidney Disease and Dialysis" recommends an intake of 30-35kcal/(kg·d) to achieve nitrogen balance.

2、More than 50% of the protein ingested must come from high-quality protein

Such as fish, lean meat, milk, eggs, beans and soy products.Fish protein is the best in animal protein, and soy protein is the best in plant protein.High-quality protein contains many types and quantities of essential amino acids, and has high nutritional value.

3、Low-protein diet plus compound α-ketoacid preparation 0.12g/(kg·d) treatment combination therapy has better effect

Alpha ketoacid is a nitrogen-free raw material for the synthesis of essential amino acids. It can be converted into essential amino acids in the body and will not cause an increase in nitrogen-containing waste.Protein restriction may lead to growth delay and reduced serum albumin levels, and ketoacid supplementation can correct these abnormalities and achieve better kidney protection than protein restriction alone.

For patients with advanced CKD who are not on dialysis, 0.6 to 0.7g/(kg·d) protein can be ingested.For GFR

4、Dialysis patients increase protein intake

The dialysis process will cause some nutrients to be lost, and the dialysis itself will be accompanied by the process of protein catabolism.Therefore, patients with CKD dialysis should increase their protein intake accordingly compared to patients without dialysis.My country recommends that patients with hemodialysis or peritoneal dialysis consume 1.0to 1.2g/(kg·d) of protein.For patients with residual renal function, it is recommended to maintain protein intake at 0.8~1.0g/(kg·d).It is reported that protein intake of about 1 g/(kg·d) is sufficient to maintain a positive nitrogen balance for patients undergoing dialysis.

5、Electrolytes and vitamins

Studies have found that salt restriction can cause blood pressure to drop and proteinuria to continue to decrease, which is conducive to reducing the incidence of cardiovascular events in patients with CKD.The Kidney Disease: Improving Global Outcomes (KDIGO) recommends that the sodium intake of patients with CKD in all stages should be less than 2 g/D.The intake of sodium salt in dialysis patients needs to be controlled at 2.0to 2.3 g/d (equivalent to 5.00 to 5.75 g/d of dietary salt).Water should also be appropriately restricted to avoid the occurrence of hyponatremia.

The presence of phosphorus in the diet includes organophosphorus and inorganic phosphorus. Organophosphorus is mostly present in proteins, while inorganic phosphorus is present in additives or preservatives.The body's absorption rate of inorganic phosphorus is 90%, while the absorption rate of organic phosphorus is 40% to 60%.Protein is an important source of phosphorus, but excessive restriction of protein intake for the purpose of phosphorus restriction may increase the risk of death and the incidence of malnutrition in patients with CKD and dialysis. It is recommended to eat foods with a low phosphorus/protein ratio.Our country's guidelines recommend that phosphorus intake should be less than 800 mg/D.

For vitamin intake, dialysis patients may be more prone to vitamin deficiency symptoms due to the loss of water-soluble vitamins in dialysis. Therefore, it is recommended to supplement with appropriate amounts of vitamin C, vitamin B6 and folic acid[.Vitamin K supplementation is good for reducing blood vessel calcification.Encourage patients with CKD to consume dietary fiber appropriately, promote intestinal peristalsis, and reduce the absorption of uremic toxins.For enteral/parenteral nutrition, if the recommended intake cannot be reached by simple dietary guidance, oral nutritional supplements should be given.If oral supplementation is limited or still cannot provide sufficient energy, it is recommended to give tube feeding or parenteral nutrition.