Glycemic index and glycemic load

The glycemic index (GI) ranks foods by how rapidly their digestible carbohydrates raise blood glucose relative to pure glucose (GI = 100). GI ≤ 55 is low, 56–69 moderate, ≥ 70 high. Because GI ignores serving size, glycemic load (GL) captures real-world impact: GL = GI × available carbohydrate (g) ÷ 100. High-GI and high-GL meals trigger rapid glucose spikes and reactive insulin surges, promoting hyperinsulinemia, oxidative stress, and low-grade inflammation — processes associated with insulin resistance, β-cell dysfunction, and accelerated biological aging. The PURE prospective cohort (Jenkins et al., NEJM 2021; 137,851 participants across five continents) found the highest versus lowest GL quintile carried a hazard ratio of 1.34 (95% CI 1.08–1.67) for major cardiovascular events in participants with pre-existing cardiovascular disease; no significant GL association was observed in the primary-prevention group. A Weizmann Institute study (Zeevi et al., Cell 2015; n = 800) demonstrated that postprandial glucose responses to identical foods vary substantially across individuals — driven by gut microbiome, genetics, and metabolic state — and that algorithm-based personalized advice outperformed GI-based recommendations in a randomized follow-up. The 2015 ICQC consensus affirms low-GI/GL diets as evidence-based strategies for preventing type 2 diabetes and coronary heart disease, noting that food processing, ripeness, and meal composition can shift a food's effective GI by 20–30 points.