Glycemic index and glycemic load are associated with some cardiovascular risk factors among the PREMIER study participants

Background: The clinical significance of glycemic index (GI) and glycemic load (GL) is inconclusive. Objective: This study was conducted to examine the association of GI and GL with clinical cardiovascular disease (CVD) risk factors including body weight, blood pressure (BP), serum lipids, fasting glucose, insulin and homocysteine over time among the PREMIER participants. Design: PREMIER was an 18-month randomized lifestyle intervention trial, conducted from 2000 to 2002, designed to help participants reduce BP by following the Dietary Approaches to Stop Hypertension (DASH) dietary pattern, losing weight, reducing sodium and increasing physical activity. GI and GL were estimated from 24 h diet recall data at baseline, 6 and 18 months after intervention. PROC MIXED model was used to examine the association of changes in GI or GL with changes in CVD risk factors. Results: A total of 756 randomized participants, 62% females and 34% African Americans and who averaged 50.0 +/- 0.3 years old and 95.3 +/- 0.7 kg, were included in this report. Neither GI nor GL changes was associated with changes in any risk factors at 6 months. At 18 months, however, the GI change was significantly and positively associated with total cholesterol (TC) change only (p<0.05, beta = 23.80 +/- 12.11 mg/dL or 0.62 +/- 0.31 mmol/L) with a significant age interaction. The GL change was significantly associated with TC (p = 0.02, beta = 0.28 +/- 0.15 mg/dL or 0.01 +/- 0.00 mmol/L) positively and with low density lipoprotein cholesterol (LDL-C) changes negatively (p = 0.03, beta = -0.01 +/- 0.00 mg/dL or -0.00 +/- 0.00 mmol/L), and significant age interactions were observed for both. Conclusion: GI and GL was associated with TC and LDL-C after controlling for energy, fat and fiber intake and other potential confounders and the associations were modified by age. Further investigation into this relationship is important because of its potential clinical impact.