Diabetes is challenging; kidney disease is challenging, says Vandana Sheth, RD, CDE, a Los Angeles dietitian and certified diabetes educator: “When you put the two together, that diagnosis can be overwhelming and pretty stressful.” People with diabetes are used to meal plans that count carbohydrates and saturated fat, but kidney disease adds to the foods-to-monitor list, which are covered in this article.         

Healthy kidneys work hard to keep vital nutrients in your body and get rid of waste products you don’t need. Every day, the two fist-sized organs that rest in the lower back on either side of your spine filter about 50 gallons of blood. Your kidneys expel toxins via urine and keep nutrients, such as salt and potassium, in perfect balance.

When the kidneys are damaged, a potential long-term complication of diabetes, they lose their ability to filter the blood properly. That’s dangerous because waste and excess fluid can’t escape your body. A meal plan that takes this into consideration is important for people with decreased kidney function and those with kidney failure on dialysis.

Protein
The nutrient protein is essential for building muscles and repairing tissues, but when your kidneys can’t filter protein waste products such as urea from your body, you run the risk of these waste products building up to high levels. This, in turn, can cause serious health problems, from fatigue and loss of appetite to a decreased level of consciousness and coma. Because of this, many people with kidney disease limit the amount of protein they eat.

Exactly how much protein is too much depends on a person’s kidney function, and the specific daily allowance is usually recommended by a doctor or dietitian. Because you won’t be eating as much of it, experts suggest sticking with high-quality protein found in lean meats, eggs, and fish. Vegetarians and vegans can get protein from soy milk, soy nuts, and tofu. (Cheese, beans, and tree nuts are good protein sources, but they’re high in phosphorus, which needs to be eaten in limited amounts with kidney disease.)

Protein needs may change should dialysis become necessary. Because protein is lost during dialysis, people with kidney failure may need to increase their protein intake, on the advice of their health care providers.

Sodium
People with diabetes are advised to reduce their sodium intake because sodium can raise blood pressure, increasing the risk for heart disease. When your kidneys don’t work properly, eating less salt becomes even more important. Too much sodium can raise blood pressure and cause swelling and fluid retention, including around your heart and lungs.

Depending on your level of kidney function, you may be advised to eat no more than 1,500 mg of sodium each day. That recommendation already applies to adult Americans over 50, African Americans, and people with high blood pressure.

Curtailing use of the saltshaker at meals is a good first step, but avoiding salty stuff means bypassing packaged foods and dining out with care. Most of the sodium in American diets is already in your food by the time you eat it. Even when they don’t taste salty, processed foods such as chips, deli meats, soup, and even sweets are often loaded with sodium, as are most restaurant meals. The smart idea: Buy unprocessed or minimally processed foods and make homemade meals. Doing so might cost a bit more than processed foods, but the payoff for your health will be worth it.

To boost the flavor of foods, consider adding herbs and spices to your meals in place of salt. “We often talk about using flavored vinegars. There’s no sodium in them, but they bring out the nice flavor and tang and tart,” says Joni Pagenkemper, MS, RD, CDE, LMNT, a registered dietitian and certified diabetes educator in Omaha, Neb.

Once your taste buds acclimate to less salt (which can take a few weeks), you’ll appreciate the way delicate flavors—such as fresh basil or a squeeze of lemon—can add interest to meals. Do stay away from salt substitutes, which can be high in potassium.

Potassium
Potassium is often touted as the counterbalance to salt because of the way it can help reduce blood pressure. But when the kidneys stop working, too much potassium can build up in the blood, and that spells danger for the heart. (Talk to your doctor about any medications that may increase your potassium levels, such as certain blood pressure meds.)

Limiting potassium can seem difficult—it’s found in fruits and vegetables, which are the cornerstones of a healthful diet. Some foods that are high in potassium include avocados, tomatoes, and potatoes. “Usually [your] fruit and vegetable intake will be totaled for the day, and you want to choose the ones lowest in potassium,” says Sharon Schatz, MS, RD, CSR, CDE, an expert in renal nutrition who works at a dialysis center in Lumberton, N.J.

Lower-potassium produce has less than 200 mg of the mineral per serving and includes berries, cherries, red grapes, plums, red cabbage, red bell peppers, broccoli florets, spinach, asparagus, and kale. “Choose an array of fruits and vegetables, different colors, so you’re getting the phytonutrients, the antioxidants,” Schatz says. Cooking food also affects its potassium content (see "Friendly Foods," below).

Phosphorus
The mineral phosphorus is found in most foods, though it appears in largest quantities in soda (there’s more in brown cola than clear), dairy products, nuts, dried beans, and some cereals.

Phosphorus and potassium seldom appear in a label’s nutrition facts; visit ndb.nal.usda.gov for a food database that lists these nutrients. Also, watch for the term sodium phosphate. “They’re adding a lot of phosphorus additives to foods,” says Schatz. “Some of the chickens now are being processed with sodium phosphate additives.” You’ll also find the additive, which extends shelf life, in processed cheese and cans of iced tea.

Phosphorus is important for bone health. But when the kidneys begin to fail, too much phosphorus can build up in the blood. Excessive phosphorus can pull calcium from your bones and put you at risk for osteoporosis. And it can cause calcium to build up elsewhere in the body, harming your organs.

It may seem like a smart idea to eat plenty of high-calcium foods when you live with kidney disease in order to make up for the calcium leached from your bones. But most foods that are high in calcium are also high in phosphorus, so the best bet is to limit the amount of phosphorus. Your doctor may prescribe a phosphate binder, which can help control how much phosphorus your body gets from food.

Fluids
Most people in the early stages of kidney disease won’t need to limit their fluids. In fact, staying hydrated is a good thing. 

Yet some people do have to monitor how much they drink. There’s no one-size-fits-all fluid limit for people with late-stage kidney disease or kidney failure. Instead, your provider will help you set indiv­idual guidelines.

Your Meal Plan
Once you’ve learned the foods to limit when your kidneys don’t function properly, the logical next question is: What can I eat? A dietitian will help you find the balance between a diabetes-friendly and kidney-friendly eating plan. For people with diabetes, kidney disease, or both, medical nutrition therapy consultations are covered by Medicare, Medicaid, and many other insurance plans.

One dietary fix is to play with portion sizes. “A good rule for all Americans is: You probably need to eat less, no matter what it is you’re eating,” says Pagenkemper.

Seeking out high-fiber foods that will fill you up is also a good idea. Some foods that are great fiber sources as well as moderate in potassium and phosphorus include cooked barley, buckwheat, green beans, cauliflower, and collard greens. Uncooked pears, tangerines, apples, berries, and bell peppers are also good choices.

The efforts you make to customize your eating plan for kidney health can have whole-body benefits. “The fact that you have diabetes [means you] already watch what you’re eating. So you’re on the right track,” says Sheth. “And now we’re tweaking it a little bit. With a little education and support, it can absolutely be done.”