Abstract
The effects of carbohydrate quality, as characterized by glycemic index (GI) and glycemic load (GL), have become a topic of interest in assessing diet's impact on chronic disease including cardiovascular disease. This review focuses on the role of GI or GL with respect to coronary heart disease, stroke, and key blood lipid biomarkers. The main body of this review emanates from the white paper completed for the Wheat Foods Council. In addition, findings from relevant papers published since the completion of the white paper will be added. Overall, the findings are mixed. In some studies, there are associations found between the risk of coronary heart disease and stroke and high-GI or -GL diet. However, roughly an equal number other studies fail to show such associations. In some cohorts, gender, body weight, or other differences such as dietary patterns may impact the associations. The most consistent associations are those observed between GL and blood lipids. High dietary GL is associated with lowered high-density lipoprotein cholesterol and increased triglyceride levels. However, the associations for GI and various lipid biomarkers are less consistent. There are several potential reasons for the inconsistencies for both biomarkers and disease endpoints. One stems from the variability of the GI and GL measurement. Other difficulties stem from (a) the application of table values for GI and GL to diets, especially those from food frequencies, and (b) the fact that diet quality of low-GI or -GL diets replete with fruits, vegetables, nuts, and whole grains may vary as GI or GL varies. Such diets have many constituents such as dietary fiber that lower cholesterol and mitigate risks independently. The findings of this review concur with those from the evidence-based review prepared for the 2010 Dietary Guidance Advisory Committee, which stated that data in the literature were inadequate to come to a firm conclusion about the relationship of GI or GL to cardiovascular disease.