Adding salt to food may increase risk for chronic kidney disease

Key takeaways:

• The link between high salt intake and chronic kidney disease was stronger in individuals with a lower BMI and physical activity level.
• Physicians should suggest reducing salt intake to patients, an expert said.

Adding salt to food — even sometimes — was linked to an increased risk for chronic kidney disease, according to a study published in JAMA Network Open.

“Adding salt to foods is a behavior reflecting long-term preference to salty diets. High sodium intake is a major risk factor for [chronic kidney disease (CKD)],” Lu Qi, MD, PhD, FAHA, HCA Regents Distinguished Chair and professor in the department of epidemiology at Tulane University School of Public Health and Tropical Medicine, told Healio. “In our previous studies, we have found that adding salt to foods at the table is related to various disorders, including cardiovascular diseases, diabetes and mortality. In our study, we found that reducing the frequency of adding salt to foods at the table was significantly related to a lower risk of chronic kidney disease.”

Qi and colleagues’ latest population-based cohort survey study consisted of 465,288 participants aged 37 to 73 years from the U.K. Biobank. The participants (mean age, 56 years; 54% women) were asked at baseline how much they added salt to their foods, with options being “never or rarely,” “sometimes,” “usually” or “always.”

Qi and colleagues found that participants who reported higher frequencies of salt intake were more likely to have a higher BMI and diminished estimated glomerular filtration rate vs. those who reported lower frequencies.

The researchers identified 22,031 documented cases of CKD during a median follow-up of 11.8 years. They found that, compared with those who reported rarely or never adding salt to food, there was an increased risk for CKD among those who reported:

• sometimes adding salt to food (adjusted HR = 1.04; 95% CI, 1-1.07);
• usually adding salt to food (aHR = 1.07; 95% CI, 1.02-1.11); and
• always adding salt to food (aHR = 1.11; 95% CI, 1.05-1.18).

“We observed that the positive association of adding salt to foods with CKD was attenuated with increased BMI and level of physical activity, as well as the presence of high cholesterol,” Qi and colleagues wrote.

The findings are consistent with previous studies “in which the positive association of the frequency of adding salt to foods with the risk of premature mortality was attenuated with increased BMI,” they wrote.

The researchers acknowledged several possible limitations to the study. For example, the self-reported data did not provide precise information on salt frequency and “might be subject to information bias,” Qi and colleagues wrote.

Ultimately, “physicians may provide suggestions to the patients to reduce adding salt to foods at the table,” Qi said, although “clinical trials are needed to provide further evidence for causality.”