Cardiovascular diseases are leading causes of morbidity and mortality, particularly in individuals with diabetes. Blood pressure, a modifiable risk factor, is influenced by dietary sodium and potassium intake. High sodium intake elevates blood pressure, while a low-sodium, high-potassium diet lowers it. Public health bodies recommend a daily sodium intake below 2300 mg (100 mmol/24 h) and potassium intake above 4680 mg (120 mmol/24 h). However, global average sodium intake significantly exceeds these recommendations. Previous research in Australia found high sodium intake in individuals with type 1 and type 2 diabetes. The necessity and feasibility of adhering to these guidelines for individuals with diabetes, especially in light of paradoxical associations between low sodium intake and increased mortality in this population, have been questioned. Studies have shown inconsistent associations between low sodium intake and mortality, with some reporting higher risk, others lower risk, a U-/J-shaped relationship, or no association. Methodological differences, particularly the use of less accurate dietary recall methods, may account for these discrepancies. The current study aimed to provide an updated assessment of adherence to sodium and potassium guidelines in a cohort of individuals with diabetes using 24-h urinary sodium (uNa) and potassium (uK) excretion, a more accurate method for estimating dietary intake than dietary recall. The hypothesis was that adherence would be low overall and that intake would remain stable over time.

The literature review section highlights the inconsistent findings regarding the relationship between dietary sodium intake and cardiovascular health outcomes. Some studies link low sodium intake to increased cardiovascular and all-cause mortality in individuals with diabetes, while others show the opposite or no association. These inconsistencies are attributed to methodological limitations in previous studies, primarily the use of less precise dietary recall methods compared to the 24-h urinary excretion used in this study, which provides a more accurate estimate of dietary sodium intake. Prior research on dietary sodium and potassium intake in people with diabetes in Australia is limited, with only a few studies assessing adherence to guidelines using 24-h urine collections, and only one study examining both type 1 and type 2 diabetes. The current study aims to address these gaps by providing an updated assessment using a larger sample size and longer follow-up period.

This prospective cohort study recruited 904 participants with diabetes from a university teaching hospital's diabetes outpatient clinics between 2009 and 2015. The primary endpoint was the assessment of adherence to dietary sodium guidelines at both the individual and cohort level using 24-h urinary sodium excretion. Secondary endpoints included the assessment of potassium intake at both the individual and cohort level. Participants provided 24-h urine samples for measurement of urinary sodium (uNa), potassium (uK), volume (uVol), and creatinine (uCr). Serum creatinine, urea, estimated glomerular filtration rate (eGFR), glycated hemoglobin (HbA1c), fasting glucose, and lipids were also measured. Clinical characteristics including age, blood pressure (BP), body mass index (BMI), and duration of diabetes were recorded. Dietary sodium and potassium intake was estimated from 24-h urinary measurements, corrected for urinary creatinine to adjust for incomplete urine collections or changes in renal function. Adherence to guidelines was defined as uNa < 2300 mg/24 h (100 mmol/24 h) for sodium and uK > 4680 mg/24 h (120 mmol/24 h) for potassium. Statistical analyses included descriptive statistics, yearly average calculations, individual-level adherence assessment, univariate and multivariate logistic regression to identify factors associated with adherence. A 10% random validity check ensured data accuracy.

A total of 3689 urine collections were analyzed, averaging four per participant. The corrected mean ± SD urinary sodium excretion was 181 ± 73 mmol/24 h, and the mean potassium excretion was 76 ± 25 mmol/24 h. Only 7% of participants met the dietary sodium guideline, and 5% met the potassium guideline. Males were less likely to meet sodium guidelines (OR 0.40, p < 0.001) but more likely to meet potassium guidelines (OR 6.13, p < 0.001). Longer duration of diabetes was associated with higher adherence to sodium (OR 1.04, p < 0.001) and potassium (OR 0.96, p = 0.006) guidelines. Increasing age was significantly associated with adherence to potassium guidelines (OR 0.97, p = 0.007). Cohort-level analysis showed mean yearly uNa and uK remaining above and below recommended levels respectively, without changes over time. Individual-level analysis revealed low and stable adherence to both guidelines over the study period. Univariate analysis revealed that male sex, duration of diabetes, and HbA1c were associated with adherence to sodium guidelines, while male sex, duration of diabetes, and age were associated with potassium guideline adherence. Multivariate analysis confirmed these associations, controlling for other variables.

The study's findings indicate poor adherence to dietary sodium and potassium guidelines among people with diabetes, with little change in intake over time. This challenges the current recommendations, particularly the stringent sodium reduction targets. The low adherence might be due to several factors including increased salt appetite, reduced salt taste perception, and high sodium content in commonly consumed processed foods. The lack of impact of food label education on sodium intake underscores the need for more comprehensive interventions. The study highlights the importance of the sodium-to-potassium ratio for cardiovascular health. The study acknowledges that the optimal range of sodium intake remains under debate; some observational studies have associated both low and high sodium intake with increased mortality, suggesting a possible U-shaped relationship. The results suggest that the majority of the participants consumed sodium within a range (115-215 mmol/24h) previously reported to be associated with better cardiovascular outcomes, questioning whether the current strict recommendations should be reevaluated. Further research, including large-scale, long-term interventional trials, is needed to determine appropriate sodium intake targets in people with diabetes.

This study demonstrates that people with diabetes do not adhere to current dietary sodium and potassium guidelines, showing minimal change in intake over time. The low adherence rates, coupled with findings from other studies indicating adverse effects of very low sodium intake, cast doubt on the current strict sodium reduction recommendations. Future research should focus on identifying effective interventions to improve dietary habits and determining optimal sodium and potassium intake targets for people with diabetes, focusing on achieving a healthy sodium-to-potassium ratio.

While the study has a relatively large sample size and utilizes accurate 24-h urine collection for dietary assessment, several limitations exist. The use of medications affecting sodium and potassium excretion was not excluded; however, the effect of these is unclear. The inconsistent number of urine collections and the time interval between collections may influence the results. The study is observational; therefore, it is not possible to infer causality. The sources of dietary sodium and potassium were not assessed formally, limiting a full understanding of dietary habits. Further research into the interactions between salt appetite, taste perception, and food choices is necessary.