Urinary Potassium Sheds Light on Diet Quality

RENO, NEV. — Twenty-four-hour urinary potassium excretion is an effective clinical marker for diet quality and can be used to identify patients with poor diets, Dr. Alexander G. Logan said at the annual meeting of the American College of Nutrition.

Physicians can use 24-hour urinary potassium excretion levels of less than 60 mmol/day in men and less than 41 mmol/day in women as a cutoff point in identifying patients with poor-quality diets.

“This is a simple test that can be done in the office,” said Dr. Logan, of Mount Sinai Hospital in Toronto.

Assessing diet quality can be a difficult process, he said, and usually involves the use of 24-hour diet recall, a food diary, or a food frequency questionnaire. But measuring 24-hour urinary potassium excretion provides an objective marker that can be used in diet counseling, he said.

Dr. Logan and his colleagues enrolled 220 patients from a regional kidney stone center in Ontario. The patients, aged 18–50 years old, had idiopathic nephrolithiasis and were on unrestricted diets. Staff at the kidney center collected information on weight, height, and blood pressure. In addition, the staff collected 24-hour urine samples and administered a structured patient interview and a food frequency questionnaire. The 166-item food frequency questionnaire was used to derive the patient's diet quality score.

Dr. Logan and his colleagues found that diet quality scores increased as urinary potassium values increased. Patients who had the lowest levels of urinary potassium had an average dietary quality score of 34, compared with a score of 76 among individuals with the highest urinary potassium levels.