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The Link Between Salt Intake and Kidney Health

Oct 31, 2023

Despite existing guidelines outlining the daily recommended intake of dietary sodium, people worldwide typically exceed these guidelines. Too much salt can increase the strain on your kidneys, making it harder for them to remove excess water from the body.

Many kidney disease patients, including those on renal replacement therapy, may need to reduce or limit the amount of salt and sodium in their daily diet.

This article discusses the difference between sodium and salt and their link to kidney health.

Key Points

  • Growing evidence shows a direct and indirect negative effect of high dietary sodium on the kidneys.
  • Dietary sodium may affect proteinuria, blood pressure control, and immunosuppressant therapy in patients with kidney disease.
  • The amount of dietary sodium is an important concern for all kidney disease patients, including those who have received a kidney transplant or are on dialysis.

Salt and Sodium

While salt and sodium sound similar and are often used interchangeably, they differ. Salt, also known as the compound sodium chloride, comprises roughly 60% chloride and 40% sodium. It is used to flavor food or as a stabilizer and binder in food products.

Sodium is a naturally occurring mineral that is essential for vital functions in the human body, such as:

  • regulating blood pressure
  • electrolyte and fluid balance
  • maintaining normal cellular homeostasis and
  • helping the nerves and the muscles to work correctly

Since the body does not make sodium, it needs to be consumed. An adult human is estimated to need about 500mg of sodium daily to support vital functions. The Daily Values are a reference for recommended amounts of nutrients to be consumed daily and not exceeded. The Daily Value for sodium is less than 2,300mg per day.

Too much sodium in the diet can negatively affect someone’s health status and lead to heart disease, high blood pressure, kidney disease, or stroke. Excess amounts of sodium may also lead to calcium loss through the bones.

Americans consume on average 1 to 1.5 teaspoons of salt or roughly 3,400mg of sodium daily. This is far more than the daily 500mg of sodium needed to sustain and facilitate vital body functions.

Sodium and the Kidneys

The body is able to remove excess water by filtering blood through the kidneys. For the kidneys to be able to pull excess water out of the bloodstream, a balance of sodium and potassium in the body is needed.

The kidneys play a crucial role in regulating blood pressure by balancing the sodium content in the body. A diet that is high in salt and sodium alters the sodium balance in the body, putting strain on the kidneys and reducing their function. A reduction in kidney function results in less excess water being removed, which increases blood pressure levels.

In addition, high sodium or salt consumption has been linked with an increase of protein in the urine, which is a significant risk factor or indicator for kidney damage. Increased sodium levels also may raise the amount of calcium in the urine, increasing the chances of someone developing kidney stones. Kidney stones can cause additional damage to the kidneys.

Kidney Disease and Sodium

How do salt and sodium affect those with kidney disease, chronic kidney disease, or end-stage kidney disease?

In chronic kidney disease (CKD) patients, increased blood pressure is a common result of high sodium or salt consumption. CKD shares risk factors with heart disease, and high blood pressure is a major risk factor for both.

High blood pressure stiffens and narrows the body’s blood vessels, reducing blood flow to the organs. The force of blood pumping through the blood vessels increases, putting strain on the heart and kidneys. The narrowing of blood vessels and reduced blood flow to the kidneys decrease their ability to effectively remove water and waste products from the bloodstream.

If the blood vessels that deliver blood to the kidneys are damaged, the kidneys will act as if there is not enough water (dehydrated). Thus, the kidneys will tell the body to retain any extra fluid or salt. With an increase in fluid and salt, hypervolemia occurs, causing blood pressure to increase. Kidney disease and CKD patients may experience increased disease progression, and if not managed or treated, heart disease or kidney failure may develop.

Sodium effects on proteinuria

In patients with CKD or kidney disease, proteinuria (the amount of albumin in the urine) is a key indicator for disease progression. It is also used to predict heart disease in both the general population and CKD patients.

Reducing dietary sodium consumption has been shown to reduce proteinuria.

Sodium and patients on renal replacement therapy

Reduced sodium consumption has benefits for people with kidney transplants. In kidney transplant patients with high blood pressure, low sodium consumption combined with blood pressure therapy shows decreased blood pressure.

Some immunosuppressants administered to kidney transplant patients may be associated with total body restriction. Thus, it may be recommended to reduce dietary sodium to help manage high blood pressure and increase body fluid.

Reducing Sodium and Salt Consumption

Salt may affect people differently, with some people being able to consume sodium without it affecting their blood pressure. Other people may be salt sensitive, where any increase in sodium consumption raises their blood pressure and reduces their kidney’s ability to regulate fluid.

What is reduced sodium?

  • Sodium-free: only the smallest possible amount of sodium per serving
  • Very-low sodium: 35mg or less per serving
  • Low sodium: 140mg or less per serving
  • Reduced sodium: Reduced sodium foods have had their sodium content reduced by 25%.
  • Light in sodium: Light in sodium products have reduced their sodium content by 50%.

A kidney-friendly eating plan is implemented to help manage and slow down kidney damage. It is designed to prevent certain minerals, such as sodium, from building up in the body. A kidney-friendly eating plan may also be used in order to avoid or manage other severe conditions, such as high blood pressure and diabetes.

Some practical tips for reducing the amount of salt that you consume:

  • Read the nutrition facts on food labels.
  • Prepare and cook your own food when you can.
  • Substitute salt for spices to add flavor.
  • Buy fresh fruit and vegetables when you can.
  • Choose low-sodium or unsalted snacks.
  • Rinse sodium-containing canned foods, such as beans.
  • Check your condiments. Many low-sodium products contain potassium chloride as a substitute, which can cause damage if you are on a restricted potassium diet.
  • Choose lower sodium options at restaurants.

If you have CKD or ESRD or are on renal replacement therapy, your nephrologist or renal dietitian may recommend that you follow a low-sodium diet, which includes reducing salt and other items with sodium-containing ingredients.

Always talk to your dietician or healthcare provider before increasing or decreasing your daily consumption of certain nutrients or foods.

Panoramic Health

Panoramic Health is an integrated value-based kidney care platform that is led by physicians with 14 years of experience providing care across the spectrum of CKD3-ESRD patients.

Patients can expect holistic care coordination from a dedicated team of care experts and nephrologists. Services include pharmacy, nutrition, PCP coordination, and SDOH services. The frequency and types of services are based on risk profile and disease stage.