Dietary Salt Intake is a Significant Determinant of Impaired Kidney Function in the General Population

Abstract

Background/Aims: Kidney dysfunction is an important risk factor for cardiovascular disease and end-stage renal disease. This study investigated whether dietary salt intake predicts deterioration of kidney function in the general population. Methods: In all, 12 126 subjects with a normal estimated glomerular filtration rate (eGFR ≥60 mL/min per 1.73m²) attending an annual check-up were enrolled in the study and were followed-up for a median of 1754 days; the endpoint was the development of impaired kidney function (eGFR < 60 mL/min per 1.73m²). Individual salt intake was estimated using spot urine analysis. Results: At baseline, mean (± SD) salt intake and eGFR were 10.6 ± 3.4 g/day and 80.8 ± 12.9 mL/min per 1.73m², respectively. During the follow-up period, 1384 subjects (25.2 per 1000 person-years) developed impaired kidney function. Multivariate Cox hazard regression analysis revealed salt intake as a significant predictor of the new onset of kidney impairment (hazard ratio 1.045; 95% confidence interval 1.025–1.065). Subjects were divided into two groups based on salt intake; the incidence of impaired kidney function was higher in the group with high than low salt intake (P < 0.001, log-rank test). Multivariate Cox hazard regression analysis indicated a 29% increased risk of developing impaired kidney function in the high-salt group. Multivariate linear regression analysis showed a significant correlation between salt intake and yearly decline in eGFR (β = 0.060, P < 0.001). Conclusion: Salt intake is associated with the development of impaired kidney function in the general population, independent of its effects on blood pressure. Salt restriction may help prevent the development of impaired kidney function.

Further evidence that methods based on spot urine samples should not be used to examine sodium‐disease relationships from the Science of Salt: A regularly updated systematic review of salt and health outcomes (November 2018 to August 2019)

“…Studies assessed for eligibility were meta‐analyses (n = 3), prospective cohort studies (n = 10), cross‐sectional studies (n = 9), post hoc analyses of RCT’s (n = 1), quasi‐experimental studies (n = 2), and modeling analyses (n = 2). Three studies assessed mortality outcomes, 22‐24 six studies assessed morbidity outcomes, 25‐30 15 studies assessed clinically relevant surrogate outcomes, 31‐45 including 12 that assessed blood pressure outcomes, 31‐34,38‐45 and three studies assessed physiologic outcomes 46‐48 . Of these studies, only two met the minimum methodological criteria for detailed critical appraisal (Table 1).…”

High Salt Diet Impacts the Risk of Sarcopenia Associated with Reduction of Skeletal Muscle Performance in the Japanese Population

“…Healthy adult volunteers ( n = 122, age (standard deviation [SD]): 56.3 (12.3) years) were recruited from the community using local advertisements, and participants were selected from Tsukuba and nearby urban areas (Ibaraki, Japan). Participants with an estimated glomerular filtration rate of 90 mL/min/1.73 m 2 or less were excluded because renal function is involved in sodium uptake and renalase levels [ 24 , 30 , 31 , 32 , 38 , 39 , 40 ]. In addition, eight participants who showed more than four times the standard deviation of the mean blood test of all 122 participants were excluded, because there was a possibility of other diseases.…”

Diet and Kidney Function: a Literature Review

“…Apart from that, there is increasing scientific interest in the potential role of diet [15,16]. High salt intake is an established risk factor for kidney function decline [17,18], mainly through its adverse effect on blood pressure and vascular health [19][20][21]. Less is known about other dietary factors.…”