Question

Renal Diets and Protein

Answer 1

People with compromised kidney function must adhere to a renal or kidney diet to cut down on the amount of waste in their blood. Wastes in the blood come from food and liquids that are consumed. When kidney function is compromised, the kidneys not filter or remove waste properly. If waste is left in the blood, it can negatively affect a patient’s electrolyte levels. Following a kidney diet may also help promote kidney function and slow the progression of complete kidney failure.

A renal diet is one that is low in sodium, phosphorous, and protein. A renal diet also emphasizes the importance of consuming high-quality protein and usually limiting fluids. Some patients may also need to limit potassium and calcium. Every person’s body is different, and therefore, it is crucial that each patient works with a renal dietitian work to come up with a diet that is tailored to the patient’s needs.

Protein is formed by linking amino acids together - not unlike pearls on a necklace. There are about 20 amino acid building blocks (depending how they are defined); out of these twenty, ten are considered essential amino acids and the other ten non-essential. An essential amino acid is one that the body cannot make and must be supplied by the diet. The non-essential amino acids are necessary for health and life, but the body can manufacture them from the other essential amino acids. Foods containing the essential amino acids are called "high biologic value" or HBV protein foods.

Protein is not a problem for healthy kidneys. Normally, protein is ingested and waste products are created, which in turn are filtered by the nephrons of the kidney. Then, with the help of additional renal proteins, the waste turns into urine. In contrast, damaged kidneys fail to remove protein waste and it accumulates in the blood.

The proper consumption of protein is tricky for Chronic Kidney Disease patients as the amount differs with each stage of disease. Protein is essential for tissue maintenance and other bodily roles, so it is important to eat the recommended amount for the specific stage of disease according to your nephrologist or renal dietician.

The protein we eat is digested and broken down into its amino acids, which our body then uses to build its own proteins. These proteins perform thousands of functions, including the formation of connective and muscle tissue, producing enzymes to promote chemical reactions, or building larger substances needed for life, like the hormone insulin or the hemoglobin in red blood cells.

Protein digestion begins in the stomach and intestines. The amino acids then go into the blood stream and are transported to other parts of the body where they are absorbed and used as needed. The body needs different amounts of the various amino acids and it is possible to eat more protein than the body needs. When this happens, the excess amino acids are removed as waste (urea is an example of a protein "waste product"). One of the most important methods of removal is through the kidneys and out in the urine.

The more amino acids that need removing, the harder the kidneys have to work. And for people with kidney disease, this can mean an acceleration of their kidney disease. So if a person stops eating protein, then they are saving their kidneys, right? No, because if we didn't eat protein, then malnutrition would develop and more illness would occur. So the solution is to eat enough protein to maintain health, but to minimize the excess amino acids and spare the kidneys. The way to do this is to eat foods with proteins that cause the least waste, that is, foods that have the right amounts (ratios) of different amino acids that the body will use most efficiently. Since we are animals, foods that come from animals (dairy foods, eggs, meat, poultry, fish) have the best combination of amino acids and produce the least waste- the "high biologic value" or HBV foods.

It is important to understand that grains, legumes (beans), fruits and vegetables all have varying amounts of protein made of the same amino acids in animal foods. They are not "bad foods"- its just that the amino acids they have are not in the same amounts that the human body can use most efficiently- that is, they produce more waste. This is not universally true, there are good quality vegetable sources such as soy beans that can also be used. People with kidney disease need to pay attention to both the amount and type of protein they eat.