What is glycemic load and why is it important?
What is glycemic load and why is it important? As explained by Drs Beulens and van der Schouw
, as the product of the glycemic index of a specific food and its carbohydrate content, and as such glycemic load represents both quantity and quality of carbohydrates (glycemic index refers to the postprandial blood glucose and insulin responses from dietary carbohydrates: the more rapidly absorbed the carbohydrate, the higher the glycemic index). Although the importance of glycemic load is based on its association with cardiac risk factors, few studies have related this factor directly to cardiovascular disease, and even in these few studies there have been conflicting results.1,2 The present study was designed to reevaluate this glycemic load-cardiovascular disease association in a large cohort (15,714 Dutch women), many of whom were overweight. The women were followed for 9 years, and a total of 799 cardiac or cerebrovascular events were recorded. Food-frequency questionnaires were used to establish dietary glycemic load and calculate glycemic indices. Pertinent data were also obtained from the Dutch National Medical Registry and National Death Registry. Statistical techniques were used to adjust for various cardiovascular risk and nutritional factors.
As the reader will appreciate, this was a complicated study to both undertake and to analyze, but I think the authors have provided useful information for clinicians to employ in their practices. Most importantly, as the authors note, this is the first study to report increased risk for cardiovascular disease in a population consuming a diet with a modest—but not excessive—glycemic load. The women most at risk for future cardiovascular events are those already overweight, which confirms results from earlier, smaller studies.
What does this study mean for the general population, who have already been warned of the dangers of diets high in saturated fats and instructed to switch from high total and saturated fat diets to diets high in carbohydrates?3 One of the lessons to be learned is that there are carbohydrates… and then there are carbohydrates. It is no longer enough to simply classify carbohydrates as either "simple" or "complex." Because dietary carbohydrates with different structures can give rise to different blood glucose and insulin responses, the authors believe that introducing the concepts of glycemic index (based on rapidity of carbohydrate absorption as noted earlier) and glycemic load (the product of glycemic index and carbohydrate content) provides a better measure of the nature of the carbohydrates in one's diet. The higher the glycemic load—but not necessarily the glycemic index—the higher the risk for subsequent cardiovascular disease. A practical solution for an individual patient is provided by the authors in their case study, which illustrates how their patient might replace high-glycemic-index foods with lower index foods. Hopefully this will translate into reduced risks for future cardiovascular events.