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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. If you have chronic kidney disease (CKD), your doctor and dietitian may advise you to follow a low-sodium diet, which includes limiting salt and other sodium containing ingredients.

Sodium's role 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  is a major source of electrolytes. Sodium contributes to:

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

How sodium affects 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 because 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.  

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 are:

• Edema: 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’re in the early stages of CKD, your doctor and dietitian will monitor your blood pressure. Sodium restriction is recommended if blood pressure is high or if you are retaining fluid.  

If you have stage 5 CKD and require dialysis, you will be asked to follow a low-sodium diet. The diet will help control blood pressure and fluid intake. Controlling sodium intake will help avoid cramping and blood pressure drops during dialysis. Your dietitian will determine how much sodium you can eat each day and counsel you on regulating it in your diet.

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, especially if your potassium level is too high. If you already use a salt substitute, inform your dietitian.

Tips for managing sodium intake

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. You will learn how to season food with lower sodium ingredients, and how much sodium can be safely included in your diet.

• Keep an accurate food diary to track your nutritional goals.
• Read food labels to see how much sodium content is in your food; hidden sodium can be found in foods that don’t even taste salty.
• Limit the amount of processed, frozen and canned foods in your diet.
• Watch out for beverages the contain added sodium.
• Try substituting fresh herbs and other spices to flavor foods.
• Report any changes to your weight or any swelling to your doctor.
• Be cautious when eating in restaurants; request for condiments and dressings on the side and avoid cured meats and soup.
• Be aware of high sodium convenience foods and instead prepare your own foods and freeze them for a later meal.