Healthy diet may decrease CKD risk in type 2 diabetes

Patients with type 2 diabetes who eat a healthy diet may have a lower risk of developing chronic kidney disease (CKD), according to a recent study.

Researchers used data from ONTARGET (Ongoing Telmisartan Alone and in Combination With Ramipril Global Endpoint Trial) to examine whether healthy diet and alcohol, protein, and sodium intake were associated with incidence or progression of CKD in patients with type 2 diabetes. Patients in ONTARGET were recruited from January 2002 to July 2003 and were followed through January 2008. Those included in the current study had no macroalbuminuria at baseline. The authors defined CKD as new microalbuminuria or macroalbuminuria or a decrease in glomerular filtration rate (GFR) or over 5% annually after 5.5 years of follow-up. Diet was assessed using the modified Alternate Healthy Eating Index (mAHEI), where higher scores indicated a healthier diet. The study results were published online Aug. 12 by JAMA Internal Medicine.

A total of 6,213 patients from ONTARGET with type 2 diabetes but no macroalbuminuria were included in the current study. Overall, 1,971 (31.7%) had incidence or progression of CKD by 5.5 years of follow-up and 516 (8.3%) died. Nine hundred seventy-nine patients (15.8%) developed new microalbuminuria (n=678) or new macroalbuminuria (n=301), and GFR declined more than 5% per year in 1,270 patients (20.4%). End-stage renal disease occurred in 33 patients (0.5%). Compared to those in the least healthy tertile of mAHEI score, participants in the healthiest tertile had a lower risk for CKD and death (adjusted odds ratios, 0.74 [95% CI, 0.64 to 0.84] and 0.61 [95% CI, 0.48 to 0.78], respectively). CKD risk was also lower in patients who ate more than three servings of fruit per week and in those who ate more total and animal protein compared with those who ate less. Sodium intake and CKD did not appear to be associated, but moderate alcohol intake appeared to reduce the risk for CKD (odds ratio, 0.75 [95% CI, 0.65 to 0.87]) and death (odds ratio, 0.69 [95% CI, 0.53 to 0.89]).

The authors noted that their study was observational and pointed out that albuminuria was measured only three times, which may have led to misclassification, and that protein intake may have been underreported, among other limitations. However, they concluded that a healthy diet lowers risk for CKD, slows progression of early kidney disease, and reduces risk for death in patients with type 2 diabetes. “Neither a low protein nor a low sodium diet, the 2 main nutritional recommendations in individuals with CKD, reduced the incidence and progression of the disease,” the authors wrote. They stated that “it may be legitimate” to recommend that patients with type 2 diabetes and vascular disease eat a healthy diet and avoid “extremes of protein and salt intake.”

An accompanying editorial noted that the study didn't adjust for overall energy intake, given that people who eat fewer calories also often eat less sodium and protein and are also “likely sicker and less physically active than those consuming a higher amount of calories,” the editorialists wrote. The editorialists also noted that the effects of different fat sources were not evaluated.

Dietary restrictions can be especially frustrating for patients in this population, the editorialists stressed. “Perhaps the best dietary advice we can give to patients with type 2 diabetes and kidney disease is the same as the advice for those who want to avoid chronic kidney disease, and the same advice for preventing and treating hypertension, and the same dietary advice for everyone,” they wrote. “Eat a diet rich in fruits and vegetables, low-fat dairy products, and whole grains while minimizing saturated and total fat.”