Sodium intake and renal outcomes: a systematic review.

BACKGROUND Sodium intake is an important determinant of blood pressure; therefore, reduction of intake may be an attractive population-based target for chronic kidney disease (CKD) prevention. Most guidelines recommend sodium intake of <2.3 g/day, based on limited evidence. We reviewed the association between sodium intake and renal outcomes. METHODS We reviewed cohort studies and clinical trials, which were retrieved by searching electronic databases, that evaluated the association between sodium intake/excretion and measures of renal function, proteinuria, or new need for dialysis. RESULTS Of 4,337 reviewed citations, seven (n = 8,129) were eligible, including six cohort studies (n = 7,942) and one clinical trial (n = 187). Four studies (n = 1,787) included patients with CKD. All four cohort studies reported that high intake (>4.6 g/day) was associated with adverse outcomes (vs. moderate/low), while none reported an increased risk with moderate intake (vs. low). Three studies (n = 6,342) included patients without CKD. Two cohort studies (n = 6,155) reported opposing directions of association between low (vs. moderate) sodium intake and renal outcomes, and one clinical trial (n = 187) reported a benefit from low intake (vs. moderate) on proteinuria but an adverse effect on serum creatinine. CONCLUSIONS Available, but limited, evidence supports an association between high sodium intake (>4.6 g/day) and adverse outcomes. However, the association with low intake (vs. moderate) is uncertain, with inconsistent findings from cohort studies. There is urgent need to clarify the long-term efficacy and safety of currently recommended low sodium intake in patients with CKD.