Key Nutrients in Managing Diabetes-Related Kidney Disease

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 most patients with advanced kidney disease are referred to a renal dietitian—a nutrition expert who specializes in kidney disease—in order to 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. There are a number of vital nutrients that should be restricted but can show up in unexpected foods, for example, and others that come in different forms (such as fats) that should be chosen carefully.

Sodium is a vital mineral in the fluids that surround cells. It works in tandem with potassium (see below) to regulate blood pressure and the amount of fluid in the body. It also helps to maintain pH balance and is vital to the proper function of the muscles and nervous system.

When kidneys start to fail, sodium can build up in cells and cause fluid to accumulate 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, according to the National Kidney Foundation (NKD). 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 buildup 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.

Most people in the United States consume much more sodium than is recommended—around 3,400 milligrams (mg) per day, according to the U.S. Centers for Disease Control and Prevention (CDC). This is about twice as much as the 2015-2020 Dietary Guidelines for Americans recommends.

People with chronic kidney disease typically are advised to consume even less sodium.

Sodium is found in table salt, of course, and so being sparing with the shaker can help lower sodium intake. But sodium also shows up in a wide variety of foods. The NKD estimates that only 10 percent of the salt Americans eat is consumed at home (in cooking and at the table).

The rest comes from store-bought and restaurant foods. 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 doctor or nutritionist.

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, when the diseased kidneys aren't able to filter it out the mineral can build up in the blood—a condition called hyperkalemia. 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 doctor will likely do monthly blood tests to monitor your potassium to make sure it hasn't reached dangerous levels.

According to the National Institutes of Health (NIH) Office of Dietary Supplements, adult men (19 and over), should get 3,400 mg of potassium daily and 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 imperiled by too much potassium should be aware of the richest food sources of the mineral so they can easily limit intake.

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 biochemical reactions: 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 build up in the body. 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 2015-2020 Dietary Guidelines, adults 19 and over should get 700 mg of phosphorus per day.

Phosphorus is found in a variety of foods and beverages, in particular:

• Beer and ale
• Cocoa and chocolate drinks
• Dark colas, including Dr. Pepper and similar peppery sodas
• Canned iced tea
• Dairy products including milk, milk-based drinks, cheese, custard and pudding, ice cream and cream-based soups
• Oysters
• Sardines
• Fish roe
• Beef liver, chicken liver, and other organ meats
• Chocolate candy
• Caramels
• Oat bran muffins
• Brewer's yeast

Carbohydrates are nutrients that serve as the primary source of energy for the body. There are two types:

• Simple carbs (basically sugars) are used nearly immediately upon consumption or energy
• Complex carbs (sometimes called starches) are converted into glycogen, which can be stored and used later for energy.

Excess carbohydrates can also be converted to fat.

When kidney disease has resulted from diabetes, managing the latter can play an important role in treating the former. 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 advises 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, and a person's age, weight, height, and activity level also are factors.

For people with diabetes, ideal carbohydrate intake also depends on daily blood glucose levels, particularly for those who take insulin to manage the disease, according to the American Diabetes Association (ADA).

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 doctor or dietitian will 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.

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. The immune system depends on protein to make antibodies. Protein molecules aid the transfer of messages between neurotransmitters in the brains. And many hormones, including insulin and other metabolism-regulating hormones, are proteins as well.

Protein molecules are made of smaller molecules called amino acids. There are twenty 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 wants to make.

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 dangerous wear-and-tear.

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. In easier terms, that comes down to 0.36 grams per pound, which equals as little as 10 percent of 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: How much a person should cut back will depend on a variety of individual factors, including whether he or she is on dialysis or not, that a doctor or nutritionist will have to consider.

Protein can be obtained from animal and from plant sources. 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 medical diseases or conditions.

Plant proteins tend to be low in one or more essential amino acids, but by combining certain ones it's possible to consume all the important amino acids when following a plant-based or vegetarian diet. Plants proteins are low in saturated fat and high in fiber as well. Plant sources of protein include beans, lentils, nuts, peanut butter, seeds, and whole grains.

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 problems than most people.

The U.S. Department of Agriculture (USDA) recommends the general population get no more than 30 percent of total calories from fat, and within that parameter, less than 10 percent of fat calories from saturated fat; in addition, the USDA advises limiting cholesterol 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, one that requires knowing which fats are unhealthy and eliminating them as much as possible while at the same time getting enough healthy fats without taking in excess calories.