Upping Dietary Potassium May Have Protective Effect in Diabetes

Pam Harrison

November 24, 2015

The higher the levels of urinary potassium excretion, the lower the risk for renal dysfunction and cardiovascular (CV) complications in patients with type 2 diabetes and normal renal function at baseline, new research suggests. The results indicate that increased potassium intake could be of benefit in such patients.

"In clinical practice, reduced-calorie and low-sodium diets are commonly recommended for patients with type 2 diabetes, but a low-calorie and low-sodium diet can be deficient in potassium," Shin-ichi Araki, MD, PhD, from Shiga University of Medical Science, Japan, told Medscape Medical News in an email.

"And while we need to do clinical trials to determine whether increasing dietary potassium is beneficial, we found that higher urinary potassium excretion was associated with a slower decline in renal function and a lower incidence of CV complications in patients with type 2 diabetes and normal renal function at study onset."

The study was published online November 6, 2015 in the Clinical Journal of the American Society of Nephrology.

High Potassium Excretion Equals Lower Complications in Diabetes

The research was part of the ongoing Shiga Prospective Observational Follow-up Study, which is designed to explore novel biomarkers, as well as genetic and clinical risk factors, for diabetic complications, in Japanese patients with type 2 diabetes.

A total of 623 patients with an estimated glomerular filtration rate (eGFR) of at least 60 mL/min/1.73 m2 at baseline were enrolled in the study between 1996 and 2003 and were followed until 2013.

The primary end point of the study was the first occurrence of any renal or CV events, which included initiation of renal-replacement therapy for end-stage renal disease and/or the occurrence of myocardial infarction, angina, stroke, peripheral vascular disease, and death from CV causes.

During a median follow-up of 11 years, 134 primary end points occurred.

"There was a gradient of higher incidence of the primary end points among patients in the lower quartiles of urinary potassium excretion," Dr Araki and colleagues note.

Compared with patients in the lowest quartile of urinary potassium excretion, patients in the third quartile were 44% less likely to reach the primary end point, while those in the fourth, highest quartile of urinary potassium excretion were 67% less likely to reach the primary end point at the end of the study interval.

Urinary Potassium Excretion (g/d) and Adjusted Hazard Ratio (HR) for Reaching the Primary End Point

  Q1 (<1.72) Q2 (1.72-2.32) Q3 (2.33-2.90) Q4 (>2.90)
All adjusted HR 1 (reference) 0.70 0.56 0.33

A higher urinary sodium/potassium ratio was also significantly associated with an 11% higher risk for reaching the primary end point (adjusted HR, 1.11).

In contrast, the adjusted hazard ratio for reaching the primary end point was not different among the quartile subgroups when stratified by urinary sodium excretion levels, as investigators point out.

"For many patients with type 2 diabetes, the most challenging part of the treatment plan is to decide what to eat," Dr Araki said.

"Our study suggests an increase in potassium intake, while restricting total energy, may be recommended to prevent renal and cardiovascular complications in patients with diabetes."

High urinary potassium excretion generally correlates with a high intake of potassium-rich foods such as fresh fruits and vegetables.

Potassium: The Forgotten Electrolyte?

Asked by Medscape Medical News to comment on the study, Jessica Kendrick, MD, MPH, associate professor of medicine, University of Colorado School of Medicine, Aurora, noted that the study does suffer from the limitation that the investigators secured only one 24-hour urine measurement at baseline, so whether that one measure is adequately predictive of what happened 11 years down the road is somewhat open to speculation.

"However, all the other studies have been done the same way, so that's what we have," she observed.

"It also reflects what I've been thinking all along, that potassium is the forgotten electrolyte — sodium gets all the press — but it really might be that potassium is the more important one," she added.

For diabetic patients without kidney disease, Dr Kendrick feels physicians can safely counsel them to consume potassium-rich foods.

"I don't see any downside to it, because we've known for a long time that high-potassium diets have a beneficial effect on blood pressure, and that's a good thing."

However, as Dr Kendrick pointed out, Dr Araki and colleagues felt that the effects of a high-potassium diet in this particular study were likely independent of its blood-pressure–lowering effect, because the benefit was still there after they adjusted for blood pressure.

The study was supported in part by the Ministry of Health, Labor, and Welfare of Japan as well as the Japan Agency for Medical Research and Development, the Salt Science Research Foundation, and research grants from AstraZeneca and Merck Sharp Dohme. Neither Dr Araki and coauthors nor Dr Kendrick had any relevant financial relationships.

Clin J Am Soc Nephrol. Published online November 6, 2015. Abstract

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