Dialysis becomes necessary when the kidneys can no longer adequately filter waste products and excess fluid from the blood. Kidney failure, or end-stage renal disease, means these organs cannot maintain the body’s internal balance. Dialysis serves as an artificial kidney, removing toxins and managing fluid levels. Since food and drink directly impact the substances being filtered, a specialized renal diet is fundamental to managing this condition.
Eating During the Dialysis Session
The question of consuming food while connected to a dialysis machine relates directly to patient safety and treatment effectiveness. Eating a full meal during a hemodialysis session is often discouraged. Digestion requires diverting blood flow to the gastrointestinal tract, which can contribute to a sudden drop in blood pressure, known as intradialytic hypotension. This complication can make the patient feel unwell and may require the session to be cut short, leading to inadequate waste and fluid removal. For this reason, many centers recommend limiting intake to a small, kidney-friendly snack or waiting until the session is complete.
Managing Key Minerals
A primary goal of the renal diet is to manage the intake of minerals that the compromised kidneys struggle to excrete, chiefly potassium, phosphorus, and sodium. The accumulation of these electrolytes and minerals between dialysis sessions can have serious consequences for the heart, bones, and circulatory system. Dietary adjustments are therefore necessary to maintain a safer range of these substances in the blood.
Potassium
Potassium is an electrolyte that plays a major role in muscle contraction, including heart rhythm. When the kidneys fail to remove sufficient potassium, the resulting high levels, or hyperkalemia, can lead to muscle weakness, irregular heartbeat, and potentially cardiac arrest. Foods to limit often include certain fruits and vegetables, such as bananas, oranges, tomatoes, potatoes, and cooked spinach.
Phosphorus
Phosphorus works closely with calcium and vitamin D to maintain bone health, but excess levels can be destructive. High phosphorus levels, called hyperphosphatemia, can pull calcium from the bones, leading to weak bones and fractures. This excess mineral can also deposit in soft tissues, causing calcification in blood vessels and organs. Because dialysis is not highly efficient at removing phosphorus, patients are often prescribed phosphate binders, which are medications taken with meals to prevent the absorption of phosphorus in the gut. Foods high in phosphorus that should be limited include dairy products, nuts, and dark-colored colas.
Sodium
Sodium, commonly known as salt, is closely linked to fluid balance and blood pressure. Since sodium causes the body to retain water, a high intake directly contributes to increased thirst and fluid accumulation between dialysis sessions. The resulting fluid overload strains the heart and makes blood pressure harder to control. Limiting sodium means avoiding processed and pre-packaged foods, reading nutrition labels diligently, and using herbs and spices instead of salt when cooking at home.
Fluid Restriction
Fluid restriction is necessary because failing kidneys cannot eliminate excess water, leading to its buildup in the body. This fluid accumulation between treatments is called interdialytic weight gain. Excessive fluid causes swelling, or edema, in the extremities and can significantly raise blood pressure. More dangerously, extra fluid can back up into the lungs, causing pulmonary edema, which severely impairs breathing and can lead to heart failure.
The fluid limit is personalized, often calculated by adding a fixed amount, such as 32 ounces, to the volume of any urine the patient still produces in a 24-hour period. Patients must track all liquids, as anything that is liquid at room temperature counts, including ice, soups, and gelatin. Practical strategies for managing thirst include limiting salty foods, as sodium increases thirst, and using small cups or glasses. Sucking on sugar-free hard candies, mints, or ice chips can also provide relief from a dry mouth while using only a minimal amount of total fluid.
Protein and Calorie Requirements
Unlike the diet recommended for earlier stages of kidney disease, which often limits protein to reduce waste products, the diet for patients on dialysis requires a higher intake of protein. This increased need is because the dialysis process itself removes protein, particularly the protein albumin, from the blood. A low albumin level is associated with poorer health outcomes, making adequate protein intake a serious concern. Patients typically require about 1.0 to 1.2 grams of protein per kilogram of body weight each day to maintain muscle mass and general health. Choosing high-quality protein sources, such as lean meats, poultry, fish, and eggs, helps ensure the body receives the necessary amino acids.
Beyond protein, sufficient calories are also necessary to prevent the body from breaking down its own muscle and fat stores for energy. Patients are advised to aim for a daily energy intake of 30 to 35 kilocalories per kilogram of ideal body weight. Getting these calories from healthy sources, including appropriate fats and carbohydrates, helps maintain energy balance and prevents malnutrition, which is a serious risk for dialysis patients.