Urine Test May ID Unhealthy Diets
THURSDAY March 26, 2009 -- Someday, a doctor's office assessment of the overall quality of your diet may come from a simple $8 urine test, researchers report.
Levels of urinary potassium correlate closely with nutrition in general, said study author Dr. Alexander Logan, a professor of medicine at the University of Toronto.
"We can identify people who are eating a poor quality diet by a simple urine test and can recommend an intervention," said Logan, who is also senior scientist at the university's Samuel Lunenfeld Research Institute.
Simply questioning people about their diet isn't as foolproof, he added. "One can get a general idea of [intake of] fruits, vegetables and dairy by asking," he said. But self-reports are notoriously inaccurate. So, Logan's team evaluated 24-hour urine samples from 220 people, aged 18 to 50, all diagnosed with kidney stones.
The participants answered food questionnaires about their food intake and had their weight, height and blood pressure measured.
Logan's team then looked to see if urinary potassium and sodium levels could correlate to diet quality.
They found that the higher the potassium level in urine, the higher the intake of recommended healthy foods such as fruits, vegetables, whole grains and low-fat dairy products.
The lower the potassium, the more likely the food reports were to include more red meat, fast food and sugary, high-calorie drinks.
Those with the highest levels of urinary potassium also tended to have a lower body mass index (BMI), lower diastolic blood pressure and a lower heart rate than did those with lower levels. For instance, people with the highest potassium levels averaged a BMI of 26.5 (under 25 is desirable), while those with the lowest potassium levels had an average BMI of 28.7 (a BMI of 30 is the accepted threshold for obesity).
Sodium levels were not associated with any of those variables, the team found.
The study is published in the April 2009 issue of The Journal of Nutrition.
The Logan research is "an excellent study," said Judith Stern, a distinguished professor of nutrition at the University of California at Davis, who was not involved in the study but reviewed it. Consumers might ask their physician for the test to see if their diet is as healthy as they might think, she said.
"This study supports the [medical] literature that the amount of potassium in urine may objectively measure diet quality," added Jeannie Gazzaniga-Moloo, a dietitian in Roseville, Calif., and a spokeswoman for the American Dietetic Association. "However, the study looked at 24-hour urine collections, which are cumbersome, time-consuming and impractical for some patients," she said.
Moloo called for more research to further validate the findings.
Logan said his team can probably simplify the test to make it a one-time measurement. In the meantime, he advises consumers to pay attention to their fruit and vegetable intake and to follow other healthy dietary guidelines, such as eating three servings of dairy products a day, choosing either low- or no-fat varieties if weight control is a concern.
Logan said his team also plans to study the value of the test in people besides those with kidney disease, including those with irritable bowel syndrome, many of whom eat a poor diet.
To learn more about the dietary guidelines, visit the U.S. Department of Health and Human Services.
Posted: March 2009