The kidneys play an important role in breaking down proteins. When you have kidney disease, they cannot perform this role as efficiently. Managing kidney disease and slowing the decline of function involves specific dietary changes, including monitoring protein intake. Research indicates that eating soy protein in lieu of animal proteins might benefit kidney disease.
Importance of Professional Guidance
While some proteins, like soy protein, might not impact the kidneys as negatively as other types of proteins, you must watch your intake of all kinds if you have kidney disease. Since diet plays such an important role in managing this condition, you should always consult with your doctor or dietitian before making any drastic changes to your eating habits, particularly changes related to protein intake. No recommendations for daily intake exist across the board and your daily limit will depend on what capacity your kidneys currently have, as well as other individual factors.
Amino Acid Balance
All foods that contain protein contain amino acids, the building blocks of this vital nutrient. Your body cannot make all of the amino acids it needs, meaning you must get them from your diet. The amount of amino acids a food contains determines whether it ranks as a high- or low-quality protein. Animal foods rank as high-quality proteins while many plant foods rank poorly because they typically do not contain a good ratio. Registered dietitian Joan Brookhyser, writing for the American Association of Kidney Patients, notes that soy protein represents a high-quality protein with a good balance of these essential amino acids.
You need high-quality protein for normal, healthy functioning, but animal proteins tax the kidneys more. While you do not totally need to give up animal foods, the amino-acid content of soy ensures getting a high-quality protein that will put less stress on your kidneys, allowing you to reduce animal proteins with less risk to overall health.
Research
An article written by Dr. James W. Anderson of the University of Kentucky, published in a 2008 edition of the "Asia Pacific Journal of Clinical Nutrition" notes that both human and animal studies have shown consumption of soy protein appears to improve renal function and reduce the loss of protein through the urine. He specifically references human research in regards to diabetes-induced renal disease -- the most common cause of kidney failure. He does note, however, that this link requires more research and not all studies have shown benefit.
A study published in a 2005 edition of "Clinical Nephrology" looked at the effects of soy consumption on the renal function of young adults with type 1 diabetes. All the subjects ate soy for eight weeks and then a soy-free diet for another eight. The study found that eating soy improved renal function. Additionally, it reduced "bad" cholesterol by 7 to 9 percent.
Warnings
Many soy products might contain large amounts of sodium, phosphorus and potassium -- three nutrients you must limit on a renal diet. Soy comes in a variety of forms and potentially problematic foods for kidney patients include miso, natto, soy flour, soy nuts, soy cheese and many "fake meat" soy products.
You do not necessarily have to avoid soy foods that might have sodium, potassium and phosphorus in high amounts, but you must limit serving sizes. For example, limit soy cheese to a 3-oz. serving, soy nuts to 1/4 cup and use "fake meat" products that have less than 500 mg a serving, explains Brookhyser.
Beneficial Soy Products
The best soy products include tofu, tempeh and soy milk. Brookhyser notes that soy milk has half the amount of phosphorus as regular milk.
