Salt Intake Increases CV Risk in Type 2 Diabetes

A team of Japanese researchers have found that higher salt intake is associated with a greater risk of cardiovascular disease in patients with type 2 diabetes.

Investigators from the University of Niigata analyzed data from 1,588 patients in the Japan Diabetes Complication Study, which included 59 university and general hospitals in Japan, in an effort to investigate the incidence of, and risk factors for, macrovascular and microvascular complications of diabetes. In their analysis, the authors found diabetic patients in the highest quartile of salt intake had a much greater risk of cardiovascular disease than those in the lowest quartile.
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The mean dietary salt intake ranged from 2.8 grams in the lowest quartile to 5.9 grams in the highest quartile. Throughout 8 years of follow-up, the researchers found in controlled analyses that patients in the highest quartile of sodium intake had a twofold increased risk of cardiovascular disease than those in the lowest quartile. The authors also reported that each 1 gram-per day increase in sodium intake was linked to a greater risk of heart and vascular disease.

While diabetes care guidelines recommend reducing salt intake, the researchers note that evidence has been based on studies of individuals without diabetes. Some work has suggested reducing salt intake is beneficial for patients with type 2 diabetes, but the relationship between sodium intake and complications from diabetes is unclear, they add.

When broken down by blood sugar control, the authors in the Niigata study found a significantly elevated risk for patients in the top quartile of salt consumption in comparison to the bottom quartile, if they had an HbA1c greater than 9 percent. However, they also discovered that risks of nephropathy, diabetic retinopathy, and all-cause mortality weren’t associated with sodium intake.

The authors point out that the study had some limitations, such as its observational nature, which could not demonstrate “cause-effect relationships as to whether medical nutritional treatment encouraging sodium reduction would reduce incident [cardiovascular disease] in clinical practice.”

Nevertheless, the significance of their findings are that “those who consumed an average of 5.9 grams of sodium per day had about a twofold risk of [cardiovascular disease] than those who consumed an average of 2.8 grams per day,” says Chika Horikowa, RD, MSc, CDE, of the department of health and nutrition at the University of Niigata, and first author of the study.

The results suggest that “dietary salt restriction as medical nutritional supplement would be useful,” says Horikowa, “to prevent complications of diabetes in patients with type 2 diabetes.”

—Mark McGraw

Reference

Horiakwa C, Yoshimura Y, et al. Dietary Sodium Intake and Incidence of Diabetes Complications in Japanese Patients with Type 2 Diabetes. J Clin Endocrinol Metab. 2014.