Diet is a key component in managing type 2 diabetes, especially for someone who has developed kidney disease as a result of their condition. This is because when the kidneys aren’t functioning normally, excess nutrients, toxins, and fluids can build up in the blood.
It’s such a concern that most patients with advanced kidney disease are referred to a renal dietitian—a nutrition expert who specializes in kidney disease. This professional can devise a personalized eating plan that takes into account specific treatment goals and health status.
It can be tricky to balance good nutrition with dietary restrictions necessary to support kidney health in diabetes. For example, there are a number of vital nutrients that should be restricted but can show up in unexpected foods. Others come in different forms (such as fats) that should be chosen carefully.
Sodium
Sodium is a vital mineral in the fluids that surround cells. It works in tandem with potassium to regulate blood pressure and the amount of fluid in the body. It also helps maintain pH balance and is vital to the proper function of the muscles and nervous system.
Why It Matters in Kidney Disease
When kidneys start to fail, sodium can accumulate in cells and cause fluid to build up in the tissues—swelling that’s known as called edema. Edema usually occurs in the face, hands, and lower extremities.
Excess sodium also causes blood pressure to rise (hypertension), shortness of breath, and fluid around the heart and lungs. Too much sodium in the diet can contribute to damage to the kidneys and exacerbate swelling.
When your kidneys are not healthy, extra sodium and fluid build up in your body. This can cause swollen ankles, puffiness, a rise in blood pressure, shortness of breath, and/or fluid around your heart and lungs.
Recommended Intake
Most people in the United States consume more sodium than is recommended—around 3,400 milligrams (mg) per day, according to the Centers for Disease Control and Prevention (CDC). The Dietary Guidelines for Americans recommends consuming less than 2,300 mg per day.
People with chronic kidney disease (CKD) typically are advised to consume even less sodium.
Sources
Sodium is found in table salt, of course, so using the salt shaker sparingly can help lower sodium intake. But sodium also shows up in a wide variety of foods. The National Kidney Foundation (NKF) estimates that only 10% of the salt Americans eat is consumed at home (in cooking and at the table). The rest comes from store-bought and restaurant foods.
Some health organizations, such as the American Heart Association, recommend most adults move toward an ideal limit of no more than 1,500 mg per day.
If you’re on a low-sodium diet to manage diabetes and/or kidney disease, it’s essential to know where sodium might be lurking so that you can keep your intake within the levels prescribed by your healthcare provider or nutritionist.
Potassium
The body needs potassium for almost everything it does, including kidney and heart function, muscle contraction, and the transmission of messages within the nervous system.
Although potassium is important for kidney function, it can be harmful if it builds up in the blood—a condition called hyperkalemia. This can happen when the kidneys are diseased.
An excess of potassium can be dangerous because it can cause an abnormal heart rhythm, which in turn can become severe enough to cause a heart attack.
If you have kidney disease, your healthcare provider will likely do monthly blood tests to monitor your potassium to make sure it hasn’t reached dangerous levels.
According to the Office of Dietary Supplements, part of the National Institutes of Health (NIH), adult men (19 and over) should get 3,400 mg of potassium daily. Adult women should take in 2,600 mg.
Potassium is found in a wide variety of foods, so it’s relatively easy to get ample amounts of it in a regular diet.
But because it’s not hard to come by, people with diabetes and/or kidney disease whose health could be negatively affected by too much potassium should be aware of the richest food sources of the mineral so they can limit intake.
Phosphorus
Phosphorus is a mineral stored mainly in bones, although smaller amounts are found in teeth, DNA, and cell membranes.
It plays a key role in many processes and reactions in the body, such as converting food into energy, muscle contraction, nerve conduction, and healthy kidney function.
Phosphorus also helps build strong bones.
When healthy and functioning normally, the kidneys filter excess phosphorus out of blood. When the kidneys are diseased, this process is impaired and phosphorus can accumulate.
Excess phosphorus pulls calcium from bones, causing them to weaken.
In addition, high phosphorus and calcium levels may lead to calcium deposits in the lungs, eyes, heart, and blood vessels, which over time can increase the risk of heart attack, stroke, or death.
According to the Dietary Guidelines for Americans, adults 19 and over should get 700 mg of phosphorus per day.
The tricky thing about phosphorus is that even when blood levels become dangerously high—what’s known as hyperphosphatemia—there are no overt symptoms. The condition usually doesn’t become evident until stage 4 chronic kidney disease.
Phosphorus is found in a variety of foods and beverages, in particular:
- Beer and aleCocoa and chocolate drinksDark sodas/colasCanned iced teaDairy products including milk, milk-based drinks, cheese, custard and pudding, ice cream and cream-based soupsOystersSardinesFish roeBeef liver, chicken liver, and other organ meatsChocolate candyCaramelsOat bran muffinsBrewer’s yeast
Carbohydrates
Carbohydrates are nutrients that serve as the primary source of energy for the body.
Phosphorus often is added to fast foods, ready-to-eat foods, canned and bottled drinks, enhanced meats, and most processed foods. To avoid phosphorus additives, look for the letters “phos” on the ingredients list. Some examples:
There are two types:
- Simple carbs (basically sugars) are used nearly immediately upon consumption for energy.Complex carbs (sometimes called starches) are converted into glycogen, which can be stored and used later for energy.
Excess carbohydrates of any kind can also be converted to fat.
Why They Matter in Kidney Disease
Managing diabetes plays an important role in treating the kidney disease it has caused.
This is because excess levels of sugar (glucose) in the blood is one of the causes of kidney damage due to diabetes.
The Dietary Guidelines for Americans advise that about half of daily calories come from carbohydrates, but it’s not quite that simple. Complex carbs are healthier than simple ones, for example. A person’s age, weight, height, and activity level also factor in.
For people with diabetes, ideal carbohydrate intake also depends on daily blood glucose levels, particularly for those who take insulin to manage the disease.
If you have kidney disease related to diabetes, it’s neither necessary nor smart to exclude carbohydrates from your diet altogether.
However, you should be extremely picky about the types of carbs you eat. Your healthcare provider or dietitian can provide you with an eating plan that’s designed specifically to meet your needs.
However, generally speaking, you’ll do best by steering clear of simple carbs and sticking to a prescribed amount of complex carbs. It also may be important that you lower your intake of carbs that are rich sources of potassium and/or phosphorus.
Protein
Protein molecules are made of smaller molecules called amino acids. There are 20 naturally occurring amino acids. When foods containing protein are eaten, the body breaks them down and reassembles the amino acids to create the protein structures it needs.
Beverages with zero carbos: water, seltzer, unsweetened coffee and iced tea, herbal tea, diet drinks
Beverages low in carbs, such as almond milk or soy milk
Low-fat and non-fat milk, Greek yogurt, kefir, and cottage cheese
Legumes (beans), peas, squash, pumpkin, sweet potatoes, corn, 100% whole grains (oatmeal, quinoa, barley, etc), non-starchy vegetables
Air-popped popcorn, whole grain crackers, whole grain cereals
Fruit juice, soda, sweetened iced tea and coffee drinks, lemonade, sports drinks, vitamin-infused water, flavored milk
White bread/rolls/bagels, Italian bread, multi-grain bread, white pasta or rice, muffins, croissants, scones, sugary cereals
Crackers, chips, pretzels, sweetened dried fruit, yogurt covered snacks, cookies, cake, ice cream, candy bars, cereal bars
Syrup, sugar (all types), honey, agave, molasses, corn syrup, fructose, high-fructose corn syrup, sucrose, dextrose, maltose, fruit juice concentrates
The human body relies on protein for just about everything.
Skin, hair, muscles, organs, and hemoglobin are made of protein. The enzymes that break down food and spark chemical reactions are proteins as well. And many hormones, including insulin and other metabolism-regulating hormones, are proteins too.
The immune system depends on protein to make antibodies. Protein molecules also aid the transfer of messages between neurotransmitters in the brains.
Why It’s Important in Kidney Disease
Damaged kidneys may not be able to remove all of the waste from the protein a person consumes. The more of this waste the kidneys have to deal with, the harder it can be on them, causing harmful wear-and-tear.
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Besides further damage to already-compromised kidneys, a build-up of protein waste can cause symptoms such as nausea, loss of appetite, weakness, and changes in the way things taste.
The Recommended Dietary Allowance for protein is 0.8 grams per kilogram of body weight. That comes down to 0.36 grams per pound, which equals as little as 10% of your daily calories.
For people with CKD, research suggests paring back on protein intake can help slow the progression of the disease. However, there are no cookie-cutter guidelines for reducing protein.
To determine how much protein you should take in every day, multiply your weight by 0.36. If you weigh 150 pounds, for example, the ideal amount of protein you should eat is 54 grams (unless you are physically active, in which case it’s more).
How much a person should cut back will depend on a variety of individual factors, including whether or not they are on dialysis.
Animal proteins have all the essential amino acids, but some sources can be very high in unhealthy (saturated) fats, such as fatty cuts of red meat, whole–milk dairy products, and egg yolks.
Fish, poultry, and low–fat or fat–free dairy products have the lowest amounts of saturated fats and are considered better choices for everyone, not just people with CKD or other diseases or conditions.
Plant sources of protein include beans, lentils, nuts, peanut butter, seeds, and whole grains. These tend to be low in one or more essential amino acids, but it’s possible to consume all the important ones when following a carefully crafted plant-based or vegetarian diet.
Plants proteins offer the additional benefits of being low in saturated fat and high in fiber as well.
Fat
Healthy fat plays a vital role in overall health. It provides energy, is a building block of membranes throughout the body, carries essential fat-soluble vitamins A, D, E, K, and carotenoids, and helps regulate blood pressure and other heart functions, according to the National Institute of Diabetes and Digestive and Kidney Disease, (NIDDKD).
Certain types of fat are unhealthy. They can raise blood cholesterol and clog blood vessels, increasing the risk of heart attack or stroke in people with CKD who already are more susceptible to these concerns than most people.
Most people in the general population should consume no more than 25% to 35% of their daily calories from dietary fats. Less than 7% of daily calories should come from saturated fat. Most people should also aim to limit cholesterol intake to less than 300 mg/day.
Knowing how much fat to include in their diet can be a balancing act for people with chronic kidney disease and the professionals who treat them. It requires knowing which fats are unhealthy and eliminating them as much as possible while making sure to get enough healthy fats without taking in excess calories.
Pizzorno J. The kidney dysfunction epidemic, part 1: causes. Integr Med (Encinitas).
National Kidney Foundation. Sodium and your CKD diet: how to spice up your cooking
U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans. 9th Edition.
American Heart Association. How much sodium should I eat per day?
American Heart Association. Hyperkalemia (High Potassium).
National Institute of Health. Potassium fact sheet for health professionals.
The Office of Disease Prevention and Health Promotion. Dietary guidelines for Americans eighth edition
American Diabetes Association. Get smart on carb counting
Wu G. Dietary protein intake and human health. Food Funct. 2016;7(3):1251-65. doi:10.1039/c5fo01530h
González-parra E, Gracia-iguacel C, Egido J, Ortiz A. Phosphorus and nutrition in chronic kidney disease. Int J Nephrol. 2012;2012:597605. DOI: 10.1155/2012/597605
National Heart, Lung and Blood Institute. How to lower cholesterol with diet.
American Diabetic Association. Carbohydrate counting.
National Institute of Diabetes and Digestive and Kidney Diseases. Nutrition for advanced chronic kidney disease in adults.
By Debra Manzella, RN
Debra Manzella, MS, RN, is a corporate clinical educator at Catholic Health System in New York with extensive experience in diabetes care.
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