Sodium and Chronic Kidney Disease

What is sodium?

Sodium is one of the most abundant elements on earth. Most people think of salt when sodium is mentioned. Salt is actually the mineral compound sodium chloride. Foods we eat may contain sodium chloride (salt) or may contain sodium in other forms. Your doctor and dietitian may advise you to follow a low sodium diet, which includes limiting salt and other sodium containing ingredients.

A short history of salt

In prehistoric times, humans existed on a diet of mostly fresh fruits and vegetables, which had very little, if any, sodium. Since salt is an important mineral to health, people would experience salt cravings. If salt was not found easily, they would travel long distances to find it. As people started living in groups and formed civilizations, salt became a commodity. Salt was prized not just for its ability to satisfy an important craving, it was used as a preservative. Meat, generously rubbed with salt or soaked in a salt water bath (or brine), would last a long time without going bad. Other foods could be preserved in the same way.

Because of its uses, salt became valuable. Early Romans even used it like money. In fact, the English word “salary” comes from the Latin word “sal,” which means “salt.” References to the value of salt still exist in the English language. When someone says a person is “worth their salt” or is “the salt of the earth,” they are referring to someone who is highly valued, just as salt was in earlier times.

How is salt used today?

Salt is used in a variety of ways. The most common use is for seasoning. Manufacturers of prepared, frozen and canned foods often use sodium to enhance the flavor of their products. Salt is also still used as a preservative.

Salt is used for non-food purposes as well, such as de-icing, soft water treatment and soap making.

The role of sodium in the body

Sodium is one of the body’s three major electrolytes (potassium and chloride are the other two). Electrolytes control the fluids going in and out of the body’s tissues and cells. Salt (which contains both sodium and chloride) is a major source of electrolytes. When the body becomes dehydrated, it loses fluid and electrolytes. That's why you'll notice sport drinks often have sodium as an ingredient.

Sodium also contributes to the following body functions:

  • regulates blood pressure and blood volume
  • helps transmit impulses for nerve function and muscle contraction
  • regulates the acid-base balance of blood and body fluids

How much sodium is enough?

The recommended intake of sodium for most healthy people is 2,400 milligrams or less each day. This equals the amount of sodium in one teaspoon of salt.

Unfortunately, many Americans consume much more than the recommended amount. This is because large amounts of sodium are used in processed foods. In fact, processed and fast foods contribute to up to three-fourths of the sodium in most diets. One slice of bread contains 150 mg sodium. A person who eats 2 slices of bread each meal consumes 900 mg sodium from bread alone. Many people are unaware they are consuming so much "hidden" sodium.

How does sodium affect people with kidney disease?

Although sodium is essential for the body functions listed above, too much sodium can be harmful for people with kidney disease. Sodium helps your body to retain a healthy fluid balance. But having renal disease means your kidneys cannot eliminate excess sodium and fluid from your body. As sodium and fluid build up in your tissues and bloodstream, your blood pressure increases and you feel uncomfortable.  

Particularly damaging is sodium's link to high blood pressure. High blood pressure can cause more damage to unhealthy kidneys. This damage further reduces kidney function, resulting in even more fluid and waste build up in the body.

Other sodium-related complications include the following:

  • Edema: noticeable swelling in your legs, hands and face
  • Heart failure: excess fluid in the bloodstream can overwork your heart making it enlarged and weak
  • Shortness of breath: fluid can build up in the lungs, making it difficult to breathe

Sodium and the renal diet

If you are in the early stages of chronic kidney disease (CKD), your doctor and dietitian will monitor your blood pressure. Controlling blood pressure is important in managing kidney disease, especially in the early stages. Sodium restriction is recommended if blood pressure is high or if you are retaining fluid. Low sodium diets range from 1,000 to 4,000 mg based on individual requirements. The average range for most low sodium diets is 2,000 to 3,000 mg a day. If you have other medical conditions, such as heart or liver disease, you may need to restrict sodium more.  

If you are at stage 5 CKD, also know as end stage renal disease (ESRD), and require dialysis you will be asked to follow a low sodium diet. The diet will help with blood pressure control.  It will also help you control thirst and fluid intake. Controlling sodium intake will help avoid cramping and blood pressure drops during dialysis. Your dietitian will determine the amount of sodium you can eat each day. You will be counseled on sources of sodium and appropriate substitutions for your diet.

What can you do to cut back on sodium?

One of the most important things you can do is talk with your dietitian. Your dietitian can help you determine the sodium content of your favorite foods and recommend ways to reduce your sodium intake. At first, you may miss the taste of salt. Gradually, however, you will start to taste more of the natural flavors in foods. You will learn how to season food with lower sodium ingredients, and how much sodium can be safely included in your diet. Your dietitian may also encourage you to keep a food diary that lists what you've eaten each day. This diary can be used to determine if changes need to be made to your diet, especially if you experience swelling or an increase in blood pressure.

Your dietitian will also coach you on identifying high sodium foods that you should avoid. Many patients are surprised to learn certain foods and beverages have so much "hidden" sodium. Hidden sodium is sodium that is present in food, but is not noticed because the food does not taste salty.

What about salt substitutes?

Ask your dietitian before you start using salt substitutes. Certain substitutes may contain potassium, which may need to be avoided on the renal diet. This is especially important if your potassium level is too high. If you already use a salt substitute, be sure to inform your dietitian.

Your dietitian will provide many suggestions for replacing salt. They will include suggestions like how to use fresh herbs and other spices to enhance the flavor of foods.

Tips for managing sodium intake

Know how much sodium you are allowed to have each day.

You can't manage your sodium intake if you don't know how much you can have. Your dietitian will tell you how many milligrams you are allowed for your individual requirements. 

Keep an accurate food diary.

Your food diary is an important tool for you and your dietitian, especially when you are learning about a new way of eating. You'll be able to see if you are hitting the nutritional goals your dietitian has set for you. You will also be able to track whether or not you are going over your amount of restricted minerals like sodium, phosphorus and potassium.

Read food labels.

Food labels provide important nutritional facts about the contents of your food. In addition to listing the amount of calories, fat, protein and carbohydrates, it will also list the amount of sodium for each serving. Be sure to check the serving size and compare it to the amount you eat. Some of the sodium ingredients used in food processing include: salt, sodium, monosodium glutamate (MSG), baking powder, baking soda, disodium phosphate, sodium benzoate, sodium hydroxide, sodium nitrite, sodium propionate and sodium sulfite.

Limit the amount of processed and canned foods in your diet.

Processed and canned foods are high in sodium. If you like the convenience of canned foods, try to find the same food canned without added salt. Another option is to use fresh or frozen foods. Some frozen foods, like vegetables, have less sodium. Watch out for fresh and frozen foods that have added sauces or marinades. Added seasonings and sauces often make the sodium content much higher.

Watch your beverage intake.

Canned or bottled drinks may not taste salty, but some beverages have added sodium. Compare labels and choose the ones lowest in sodium. Avoid sports beverages that contain added sodium.

Try substituting fresh herbs and other spices to flavor foods.

You'd be surprised how easy and tasty this can be. Try planting your own fresh herb garden. Look for sodium free, potassium free herb combinations such as Mrs. Dash® herb seasoning. Make your own herb seasonings with combinations of the flavors you like most.

Report any changes to your weight or any swelling to your doctor.

This may be a sign that you are consuming too much sodium. Your dietitian will assess sodium intake from the foods you eat and help make adjustments.

Be cautious when eating in restaurants.

Request foods be prepared without MSG or salt; request condiments and salad dressings the side; avoid cured or salted meats such as: ham, sausage, bacon, hot dogs and luncheon meats; avoid soups—these are very high in sodium.

 Be aware of high sodium convenience foods.

Frozen dinners and entrees, dry noodle and rice mixes, Ramon noodles and “heat and eat” burritos are among some of the high sodium convenience foods. Prepare your own foods and freeze them for a quick meal later.

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