Effects of carbohydrate quality and amount on plasma lactate: results from the OmniCarb trial

Abstract

Introduction: Plasma lactate is a marker of non-oxidative glucose metabolism associated with progression to diabetes. We examined the effect of carbohydrate quality (glycemic index (GI)) and amount (%kcal) on plasma lactate. We hypothesized that low GI (≤45 (g)) versus high (≥65 (G)) and low %kcal from carbohydrate (40% kcal (c)) versus high (58% kcal (C)) each would reduce lactate levels.

Research design and methods: We measured lactate in OmniCarb, a randomized, cross-over trial of four diets in overweight/obese adults without diabetes or cardiovascular disease (N=163). The four diets were high carbohydrate+high GI (CG, reference), high carbohydrate+low GI (Cg), low carbohydrate+high GI (cG), and low carbohydrate+low GI (cg). Participants (N=163) consumed each of the four diets over a 5-week period, separated by 2-week washout periods. Plasma lactate levels were measured at baseline, during which the participants consumed their own diets, and after each 5-week period.

Results: Baseline plasma lactate was 1.2 mmol/L. In the setting of high carbohydrate amount, reducing GI lowered plasma lactate non-significantly by 0.08 mmol/L (Cg vs CG: 95% CI -0.16 to 0.00; p=0.06). In the setting of high GI, reducing carbohydrate amount lowered plasma lactate by 0.10 mmol/L (cG vs CG: 95% CI -0.19 to -0.02; p=0.02). The combined effect of reducing GI and carbohydrate proportion in the diet (cg vs CG) was similar (cg vs CG: -0.08; 95% CI -0.16 to 0.00; p=0.04). All four diets reduced plasma lactate compared with baseline.

Conclusions: Compared with a diet with high GI and high carbohydrate amount, diets with low GI and/or low carbohydrate amount reduced plasma lactate. Whether this change in lactate leads to long-term change in glucose metabolism needs to be examined.

Trial registration number: NCT00608049.

Keywords: carbohydrates; diet; insulin resistance; lactic acidosis.

Figure 1

Participant flow diagram in the OmniCarb study. BL, baseline; CG, high carbohydrate, high glycemic index diet; Cg, high carbohydrate, low glycemic index diet; cG, low carbohydrate, high glycemic index diet; cg, low carbohydrate, low glycemic index diet.

Figure 2

Between-diet comparisons of change in lactate. In each comparison, the result displayed is the first diet compared with the second diet. For example, cg vs cG means cg minus cG, and so on. CG, high carbohydrate, high glycemic index diet; Cg, high carbohydrate, low glycemic index diet; cG, low carbohydrate, high glycemic index diet; cg, low carbohydrate, low glycemic index diet; GI, glycemic index.