High levels of salt added to food up CKD risk

Frequently adding salt to food significantly increases the risk of chronic kidney disease (CKD) in the general population, according to a recent study.

“The association of high sodium consumption with hypertension has been well established in previous studies. On one hand, hypertension is associated with an increased risk of CKD; on the other hand, hypertension often coexists with CKD and shares several common risk associations, especially sodium intake,” said the researchers.

Using data from the UK Biobank, in the prospective cohort analysis of 465,288 CKD-free participants (mean age 56.32 years, 54.83 percent female), 22,031 CKD events occurred during a median follow-up of 11.8 years. [JAMA Network Open 2023;doi:10.1001/jamanetworkopen.2023.49930]

In this study, higher self-reported frequency of adding salt to food was categorized as sometimes, usually, or always, while lower frequency was categorized as never or rarely.

Individuals who reported sometimes or usually adding salt to their food were more likely to develop CKD than those who never or rarely consumed salt (adjusted hazard ratios [adjHRs], 1.04 and 1.07, respectively; p_trend<0.001), particularly those who reported always adding salt to food (adjHR, 1.29; p_trend<0.001), after adjustment for covariates.

In addition, estimated glomerular filtration rate (eGFR), body mass index (BMI), and physical activity significantly modified the associations between adding salt to food and CKD risk. Notably, these associations were more pronounced among participants with higher eGFRs and lower BMIs and physical activity levels, the researchers noted.

When the analysis was stratified by eGFR, participants with an eGFR of ≥90 or ≥60 to <90 mL/min/1.73m² who frequently added salt to their food demonstrated a significantly higher risk of CKD than those who never or rarely did (HRs, 1.00–1.14; p_trend<0.001 and 1.00–1.08; p_trend=0.04, respectively).

Among individuals with a normal BMI or who were overweight, a significant increase in CKD risk was also observed in the higher salt intake group than in the lower salt intake group (HRs, 1.07–1.19; ptrend=0.002 and 1.04–1.15; p_trend<0.001, respectively).

Although not significant, an increased risk of CKD was also observed among obese individuals who reported frequently vs never or rarely adding salt to their food (HRs, 1.01–1.07; p_trend=0.36).

“Intriguingly, we found that the positive associations of the self-reported frequency of adding salt to food with CKD risk appeared to be attenuated by a higher BMI,” the researchers noted.

Also, in individuals without regular physical activity (<150 minutes/week), a higher salt intake was associated with a significant increase in CKD risk compared with a lower intake of salt.

“[Taken together,] we found that the positive association was increased among participants with a normal or higher eGFR, whereas the positive association appeared to be attenuated among participants with obesity and those who were physically active,” the researchers noted.

“[Overall, our study showed] that the higher self-reported frequency of adding salt to food was significantly associated with a higher risk of … incident CKD independent of socioeconomic and lifestyle factors, as well as other traditional factors associated with increased risk of CKD,” said the researchers.

“These findings support the reduction of adding salt to food as a potential intervention strategy for CKD prevention,” they noted. “However, post hoc analysis or follow-up studies to clinical trials are necessary to validate these findings.”