Urinary sodium and potassium in a sample of healthy adults in Sydney, Australia

Australia has had an official guideline for the last ten years, that people should aim to consume less than 100 mmol sodium per day (equivalent to 6.0 g NaCl). The only practical way of estimating sodium intake is from the 24-h urinary sodium excretion. Between 1970 and 1980 average sodium excretions in different Australian surveys ranged from 130 to 200 mmol/day (middle number 165 mmol/d). These surveys involved small numbers of subjects (n = 11 to 259) . To see how Australians are responding to the guidelines and taking advantage of a range of reduced salt food products now in the supermarkets, we measured urinary sodium and potassium in 117 healthy adult subjects, mostly in the university community. In group N (nutrition personnel) sodium excretion averaged 128 mmol/d in females and 137 mmol/d in males. In group W (eating a western, traditional Australian diet, no special knowledge of nutrition) urinary sodiums averaged 133 mmol/d (female) and 159 mmol/d (male). In group A (eating an Asian diet) sodiums averaged 140 mmol/d (female) and 195 mmol/d (male). Potassium excretions were 73, 81, 72, 76, 53, and 65 mmol/day respectively in the six subgroups. We conclude that these results possibly reflect a small downward trend in Australian sodium intake and that sodium intake is lower in mainline Australian diets than Asian diets. But only a minority of subjects' urinary sodiums were within the recommended 40 to 100 mmol/d. Women excreted consistently smaller amounts of sodium than men; the guidelines for sodium should perhaps be expressed separately by gender. In six subjects who provided seven days' urine collections the coefficient of variation for sodium excretion was between 20 and 35%.