By Lesley L. McPhatter, MS, RD, CSR

Controlling blood pressure and limiting the loss of protein in the urine (proteinuria) are the cornerstones of treatment in the progression of chronic kidney disease (CKD). Controlling blood pressure is best achieved by maintaining an appropriate body weight for height, limiting sodium (salt) intake in the diet, exercise and taking appropriate blood pressure medicines. Limiting protein in the diet may be useful in decreasing protein losses in the urine. Protein restriction limits phosphorus intake and total calorie intake which may help slow disease progression.

High levels of fat in the blood (Hyperlipidemia) is also a risk factor for the progression of CKD and so limiting total fat, cholesterol and saturated fat in the diet are also important. People with diabetes must also carefully monitor their diet to achieve maximum control of their blood sugar levels. Based on these important facts, diet plays a critical role in the maintenance of maximum kidney function in people with CKD.

With the resurgence of the Atkin’s diet in the 1990s, followed by the South Beach diet, many people have chosen to attempt a high protein diet for weight loss. Though scientifically unsound and with results that mimic those of all other diets with regards to dropout rate and long term weight loss, these diets have created a huge market for high protein food items.

Additionally, there has always been a push to increase protein in the diet of athletes to increase muscle mass. Though endurance training athletes do require slightly larger amounts of protein than people who do not exercise routinely (1.2gram (g) of protein per kilogram (kg) of body weight versus 0.8g/kg body weight). This is easily met by increasing the dietary intake of dairy or meat products only slightly. For example, a non-athletic 170lb (77kg) male requires 62g of protein per day. The same size endurance athlete male requires 92g protein per day or 30 additional grams. The difference can be made up by adding two ounces of meat and two cups of milk to the diet, or by adding 1.5 cup of beans and two eggs to the diet or any combination of the above.

Most Americans eat twice as much protein as required and therefore adding protein to the diet is rarely needed in healthy people. Recreational athletes do not typically need to exceed the protein needs of any healthy Americans. Vegetarians can obtain adequate protein with beans, starches and nuts. (1) The optimal diet should consist of ten percent protein and 30 percent fat (ten percent or less from saturated fat) and 60 percent carbohydrate. This is based on the Reference Daily Intakes (RDIs), which is based on the National Academy of Science’s

Recommended Daily Allowances (RDAs).(2) Calorie needs are based on body weight, exercise regime and need to gain, lose or maintain weight.

Patients with CKD are encouraged to limit protein intake to 0.8g/kg body weight, the RDA for protein for all adults. Limiting protein in the diet also helps to limit dietary phosphorus, a mineral that has been found to play a role in the progression of kidney disease. People with CKD are encouraged to limit phosphorus to 800mg/day or about 10mg/kg body weight. (3) Protein bars, as they are advertised in conjunction with many higher protein diets, are popular for muscle building and endurance exercise. Depending on the calorie level and the marketing objective of the bar, some contain more than half the recommended daily intake for our 77kg male. Powerbar® ProteinPlus™ contains 23g of protein in 290 calories. It also contains 350mg phosphorus, or 44 percent of the 800mg daily limit. Other bars do not have quite as much protein and phosphorus, but can still take up a substantial portion of daily intake. Powerbar® Triple Threat™ contains 10g protein in 230 calories and 150mg phosphorus. ZonePerfect® bars contain 14g of protein in 210 calories and 200mg phosphorus. Though the phosphorus content is lower, these products have phosphate additives, as do many prepared foods today. Dietary phosphorus (phosphorus naturally occurring in food) is absorbed at about 60 percent. Additive phosphorus is absorbed at 100 percent. For example, if you eat a lean chicken breast, only 60 percent of the phosphorus in the chicken will be absorbed by the body. In a food using phosphorus as an additive and containing natural phosphorus, the absorption will be higher. Additionally, many of these products contain a variety of vitamins and minerals, sometimes in excessive amounts that may actually be harmful in people with CKD. See Table 1 for a review of commonly used products.

Today’s market offers a variety of diet and food options. Dietary products, supplements and diets are a multibillion dollar business. Although many of these items make claims of improved health and nutrition and offer wonderful success stories of weight loss or improved health, most are unsubstantiated and many claims are false and/ or unproven. This leaves consumers with many questions and few answers concerning the best way to maintain a healthy diet and lifestyle.

People with chronic illnesses are further bombarded with products that may claim to cure or improve their particular ailment. The simplest way to a healthy diet and lifestyle is just that: simplicity. A diet with a lot of variety that includes adequate protein, fats and carbohydrates and a regular exercise program are the best ways to maintain good health.

People with kidney disease may need some additional medications and adaptations of a healthy meal plan, but the diet should be made up of whole foods with a focus on lean meats, whole fruits and vegetables, and limited fats. Picking a healthy diet is individualized, and is best done with the help of a registered dietitian that can help ensure the diet is adequate and also allows for maximum adherence to the diet plan. Before trying any new food product or nutritional supplement, people with CKD or any chronic disease should talk to their healthcare team to guarantee the product is nutritionally appropriate.

References

1. Sports Nutrition Guidebook, 3rd Edition, Clark, N. 2003, pp162-164

2. ‘Daily Values’ Encourage Healthy Diet, Kurtzwell, P., www.fda.gov

3. Clinical Practice Guidelines for Nutrition in Chronic Renal Failure, American Journal of Kidney Disease Vol 35, No 6, Suppl 2 June 2000

Lesley L. McPhatter, MS, RD, CSR, is a registered dietitian with 18 years experience with the Lynchburg Dialysis Facility (now part of the University of VA Renal Services). She’s a diet educator with all stages of CKD patients including early stages, transplant, peritoneal and hemodialysis.