Sprinkling Salt on Food Linked to Kidney Disease

New research found that excess salt use may impact kidney health by triggering biological mechanisms associated with chronic kidney disease.

Consuming salt, AKA sodium, is necessary for the human body to function. However, too much salt can lead to a host of health problems, as it can increase blood pressure and raise a person's risk of cardiovascular disease.

Moreover, recent research suggests that sprinkling salt on food may increase the risk of developing type 2 diabetes.

Because of salt's negative impact on health, the World Health Organization (WHO) recently recommended global sodium reduction policies to lower the risks of stroke, heart attack, and other conditions associated with salt consumption.

While the dangers of excess salt are well known, and scientists have thoroughly investigated the associations between high sodium consumption and cardiovascular health, salt's effects on the kidneys are less clear.

A new study published on December 28 in JAMA Network Open took a closer look at whether adding salt to a meal impacted kidney health. Their findings suggest that habitual salt use at the dinner table may increase the likelihood a person develops chronic kidney disease (CKD).

The population-based cohort study assessed 465,288 participants aged 37 to 73 years from the UK Biobank who were free of CKD when enrolled in the study from 2006 to 2010.

The researchers gathered the participants' self-reported salt use data and categorized them into groups based on whether they (1) never or rarely, (2) sometimes, (3) usually, or (4) always added salt to foods. In addition, the team accounted for lifestyle and other factors that may contribute to CKD.

During the study's follow-up period, 22,031 participants developed kidney disease.

After analyzing the data, the team found that individuals who reported using salt on their food "sometimes" had a 4% higher risk of CKD, and participants who claimed they "usually" add extra salt to their food had a 7% higher risk.

Moreover, participants who said they "always" sprinkled salt on their meals had an 11% increased risk of developing CKD.

The scientists say this increased risk revealed in the study was independent of socioeconomic, lifestyle, and other factors associated with a higher risk of kidney disease.

Additionally, the links between adding extra salt to food and an increased risk of kidney disease were more pronounced in participants with a lower body mass index (BMI) and those with a low physical activity level. The risk was also increased in individuals with a higher glomerular filtration rate (GFR).

The researchers suspect that salt intake might impact systolic blood pressure in people with a lower body weight more so than those with higher BMIs or obesity, which may explain the higher CKD risk among people with lower BMIs.

Moreover, the team suggests that regular exercise may lessen the impact of adding salt to foods.

The scientists also noted that associations between salt intake, higher GFRs, and increased risk of CKD appeared to be partly related to smoking, as people who smoke may have a higher taste for salt.

Why would adding salt to food impact kidney health?

The research team suspects that several biological mechanisms may explain the increased CKD risks found in the study. For example, elevated sodium intake is associated with extracellular fluid volume, increased oxidative stress, proinflammatory cytokines, and stiffening of the arteries — all of which are linked to CKD.

Still, there were several limitations to the study. For example, the participants' salt intake was self-reported, so sodium consumption data may not have been entirely accurate. In addition, the scientists could not determine if adding extra salt to food indicated the person had an unhealthy lifestyle. Moreover, most participants were of European descent, so it's unclear if the results would be the same among other populations.

Nonetheless, the study authors say the findings remained consistent even after carefully adjusting for lifestyle factors. Therefore, they conclude that to protect kidney health, a person might want to consider passing on the salt the next time they sit down at the dinner table.

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