Does High Salt Intake Lead to Chronic Kidney Disease?

Salt and kidney disease are interlinked. We know taking excessive amounts of salt is bad for people with kidney disease, hypertension, heart failure, and fluid-overloaded conditions.

However, whether salt intake increases the risk of kidney failure is not known. This is very important for people who are at risk of kidney failure.

Known risk factors for chronic kidney disease include:

• Hypertension
• Diabetes
• Obesity
• Family history of kidney disease
• Smoking
• Nephrotoxic drugs
• Autoimmune conditions such as lupus
• Kidney stones, and
• Certain genetic disorders like Lawrence-Moon-Bardet-Biedl syndrome

A recent study highlighted the importance of salt intake and kidney disease. The association between salt and kidney disease was made after the investigators studied a cohort of about half a million individuals without kidney disease.

Here are key points from the study:

• The study included almost half a million individuals involved in this study, aged 37-73 without chronic kidney disease (CKD) at the start in 2006-2010.
• Participants who reported frequent intake of salt in their food were at a higher risk for CKD during the 11.8-year follow-up compared to those who rarely added salt.
• A higher salt intake was constantly linked to a higher risk for CKD. The trend was more common in people who usually or always added salt compared to those who rarely added salt.
• This association was impacted by factors like kidney function (eGFR), body weight (BMI), and physical activity level.
• Researchers found that limiting salt intake is a smart strategy to lower CKD risk in the general population.

Salt and Kidney Disease:

Salt is needed for our body to work properly, helping with things like absorbing nutrients and keeping fluids balanced.

But having too much salt can increase the risk of high blood pressure, which might lead to kidney problems.

What is too much sodium?

The maximum recommended intake of salt for the general population is 2300 mg. For people with kidney disease, the maximum recommended intake of salt is 1500 mg.

When you read food labels, you may find “salt-free“, “low salt“, or “light in sodium“. Here is a table that tells you what these terms mean:

However, there’s not enough research to be sure about how salt affects the risk of kidney issues in the general population because most studies focus on people who already have certain health conditions like diabetes or high blood pressure.

Globally, 10% of the population is diagnosed with CKD each year and several of them die due to lack of treatment. [ref]

If CKD is identified on time or is controlled by modifying dietary practices, this number can be lowered greatly.

A study published in December 2023 analyzed the association between sodium consumption and chronic kidney disease (CKD). Their conclusion was as follows.

The research findings show a direct correlation between an elevated risk of chronic kidney disease (CKD) and an increased self-reported habit of adding salt to diets [ref]

Limiting salt is as important as limiting high-caloric high glycemic foods in diabetic patients. A diet low in sodium may reduce the risks of developing chronic kidney disease, especially in high-risk individuals.

Given the substantial long-term health implications and the considerable financial strain associated with treating kidney disease, particularly through dialysis, it is advisable to promote reduced salt intake.

Study methodology:

It was approved by Tulane University and subjects with incomplete data or prevalent CKD were excluded.

Over 465,288 participants (aged 37-73) were included in this study, recruited from England, Scotland, and Wales, between 2006 and 2010.

Data on salt consumption was collected via a touch screen questionnaire. Using diagnostic codes and medical records from databases, the study tracked participants over time to identify cases of chronic kidney disease (CKD).

Considerations were age, sex, race, socioeconomic status, history of health issues, smoking, drinking, physical activity, and BMI.

Hazard ratios (HRs) were calculated using Cox proportional hazard models, adjusting for various factors.

The study explored trends in CKD risk associated with self-reported salt frequency and conducted subgroup analyses.

Several sensitivity analyses were performed, excluding participants with baseline hypertension, diabetes, or CVD, and considering other factors to ensure the accuracy of findings.

The study used SAS statistical software, and data analysis occurred between October 2022 and April 2023.

Salt and Kidney Disease: Study analysis:

The average age of subjects was around 56 years and those who sprinkled more salt were mostly Asian, Black, Chinese, or a mix of races.

Also, they tended to carry a bit more weight (higher BMI) and had a lower baseline kidney function.

They also had some lifestyle differences. They were more likely to smoke, less likely to enjoy a drink, or hit the gym regularly, and their dietary habits were rather poor.

Tracking them for over 11 years, researchers found a significant number – 22,031 cases – of chronic kidney disease (CKD).

What’s striking is that even after considering different factors like lifestyle and health conditions, the risk of CKD was still higher for those who reported shaking more salt onto their plates.

So, it seems like their salt habits might be linked to a higher risk of kidney issues down the road.

This risk was more evident in people who had:

• higher kidney function
• lower BMI
• lower physical activity.

These findings were consistent which justifies their validity.

The bottom line:

Because there is an increasing number of deaths caused by CKD each year there needs to be a preventative measure.

The general public needs to be made aware of the hazards caused by increased salt intake. So, they can avoid excessive consumption or limit it to a few teaspoons only.

Sodium is hidden in prepared foods already so adding extra is not a wise option. A daily intake of 2000-2300 mg is recommended for people aged 14 or above. [ref]

Taking this into consideration, for improved and healthy kidney function in the long term, limiting salt intake is the best approach.