Abstract 21: The Effects of Carbohydrate Amount and Type on Kidney Function in Healthy Adults: Results From the Omnicarb Trial
Background: While there is considerable interest in the effect of glycemic index (GI) and amount of carbohydrate (%carb) on health, few studies have examined the effects of GI and %carb on kidney function, an important risk factor for cardiovascular disease. We determined the effects of reducing GI and %carb on kidney function.
Methods: We conducted a four-period, randomized, crossover feeding study in overweight/obese adults without diabetes or kidney disease (N=163). Participants were fed each of four diets for 5 weeks, separated by 2-week washout periods. Weight was held constant. The four diets were: high GI (GI >65) with high %carb (58% kcal from carbohydrates) (reference diet), low GI (GI <45) with low %carb (40% kcal from carbohydrates), low GI with high %carb; and high GI with low %carb. Plasma was collected at baseline and at the end of each feeding period. Primary outcomes were β2-microglobulin, cystatin C, and estimated glomerular filtration rate based on cystatin C (eGFRcys). Instead of serum creatinine (a biomarker that rises with protein intake), we used β2-microglobulin and cystatin C, which are not appreciably affected by protein intake.
Results: Mean (SD) age was 53 (11) years; 52% were women and 40% were non-Hispanic African American. At baseline, mean (SD) β2-microglobulin, cystatin C, and eGFRcys were 1.9 (0.4), 0.8 (0.1), and 104 (16), respectively. Compared to the reference diet, reducing either GI or %carb was associated with significant reductions in β2-microglobulin (P-values ≤ 0.05) and cystatin C (P-values < 0.001) as well as significant increases in eGFRcys (P-values < 0.001). The low GI and low %carb diet was associated with even greater reductions in both cystatin C (P < 0.001) and β2M (P < 0.001), and an increase in eGFRcys of 4.5 mL/min/1.73m2 (95% CI: 3.5, 5.4; P < 0.001) (Figure).
Conclusions: Reducing dietary GI and %carb increased glomerular filtration. Future studies on glycemic index and kidney function should examine the long-term effects of this increase in GFR on cardiovascular events.
Author Disclosures: S.P. Juraschek: None. A.R. Chang: None. L.J. Appel: None. C.A.M. Anderson: None. D.C. Crews: None. J. Charleston: None. E.R. Miller: None.
- © 2015 by American Heart Association, Inc.