High sodium and low potassium intake in patients with Type 2 diabetes

To document dietary sodium and potassium intake and adherence to the Australian National Heart Foundation (NHF) guidelines in patients with Type 2 diabetes mellitus attending an Australian tertiary referral and university teaching hospital.

In a longitudinal study, 24h urinary sodium (uNa), potassium (uK), creatinine (uCr), urea (uUrea) and glucose (uGlu) excretions, urine volume (uVol) and body mass index were recorded in 122 regular attenders over an 8 year period (2001-2008; mean of 1.9 samples/patient/year). In a cross-sectional study, the same measurements were recorded in patients providing urine samples in the month of June from 2001 to 2009 (782 patients, averaging 87/year).

In the longitudinal study, uNa (mmol/24 h) was 170 ± 53 (mean ± SD) in males and 142 ± 51 in females, whereas uK (mmol/24 h) was 75 ± 22 in males and 62 ± 18 in females. Once adjusted for insensible losses, only 3% of males and 14% of females met the NHF dietary sodium intake guidelines, and 14% of males and 3% of female patients met the NHF dietary potassium guidelines. Body mass index, uUrea, uVol and uGlu were independent predictors of uNa (adjusted r(2) =0.57, P<0.0001). The mean intra-individual coefficient of variation of the corrected uNa was 21 ± 1%. The cross-sectional study confirmed these findings, and no temporal trends were observed. There was no correlation with glycated haemoglobin to suggest natriuresis with hyperglycaemia.

Most patients with Type 2 diabetes mellitus do not meet NHF sodium or potassium intake guidelines. A diet high in sodium and low in potassium may contribute to the development of hypertension and to resistance to blood-pressure-lowering therapies.