1. The Glycemic Index & Load Fasih Hameed, MD IM Fellow 2008

2. Glycemic Index: Overview chemical classification of carbohydrate (simple or complex, sugars or starches, available or unavailable) Provides insight into physiologic effects of carbohydrate intake & health. Delineates measured, functional response of body to foods we eat.

3. Glycemic Index: Definition Measure of relative glycemic response to dietary carbohydrates Rate and degree of blood sugar elevation following consumption. Reference food: –White bread or Glucose = 100 –Higher index  faster and greater rise of postprandial glucose and/or insulin

4. Glycemic Index: Testing Methods 5-20 Fasting subjects 50g carbohydrate load of food administered Serum glucose measured and plotted 2-3 hour postprandial Repeated daily Measured as percent difference in area under curve vs. reference food (100)

5. Bjorck I, et al: Food properties affecting the digestion and absorption of carbohydrates. Am J Clin Nutr 59: 1994

6. Glycemic Load Accounts for average load of carbohydrate in food serving (GI x Carbs per serving [gr])/100 more accurate measure of effect on pancreatic insulin release and serum glucose levels Low GI generally = Low GL …But High GI can sometimes ≠ high GL (ie. Watermelon GI = 72, GL = 4)

7. Influences on rate of gastric emptying, digestion, absorption Soluble Fiber, reduces GI Glucose vs. Fructose (more slowly absorbed) Antinutrients (lectins, phytates, enzyme inhibitors) debatable impact Starch type: Amylose vs. Amylopectin (white vs. basmati rice) Boiled vs. Par Boiled vs. Raw Particle size, processing method: Whole grain vs. cracked vs. powderized vs. puffed Al dente vs. well done

8. Influences on rate of gastric emptying, digestion, absorption Genetic variation of plants Ripeness –Under-ripe bananas GI : 43 –Over-ripe bananas GI: 74 Protein & Fat –second meal effect –delayed emptying Acid (sourdough, lemon, vinegar)

9. Goals GL ~ 60-80 QD GI average ~50-55

10. Health Impacts Prospective studies show High GL diet linked with DM2, CAD, Cancers. Low GL diet  sustained improvements in abdominal obesity, cholesterol, and glycemic control High GL diet  fatigue (rebound hypoglycemia) Low GI/L meal  lower glycemic response at next meal. High GI diet  Insulin resitance & DM2. Low GL foods  consume smaller meals, mid meal cravings diminished.

11. Low GI vs High GI x 2 weeks 37% lower 12hr blood glucose 16% lower avg daily BG 9% lower A1C 7% lower fructosamine

12. Health impacts Low GI meal  less consumption at next meal ( overweight adolescent boys) Low GI foods  increased serum CCK “satiety peptide” Increased exercise performance Reduced LDL & Triglycerides –Release of Free Fatty Acids after rapid drop in BG

13. Clinical Utility DM2 –2004 metanalysis supporting role Cardiovascular disease –Reductions in cholesterol, but need larger studies to determine mortality impacts Anti-inflammatory diet –DM: hyperglycemia  reactive oxygen species  lipid peroxidation  atherosclerosis. –Non-DM: Hyperglycemia  production of reactive oxygen species  resultant oxidative cellular damage  inflammatory responses. Cancers –High GI associated with increased Gastric, colorectal, & upper GI cancers. –Slightly higher risks of endometrial & pancreatic. –No apparent impact on Breast CA.

14. Factors to Consider No “Good” or “Bad” Foods Remember Glycemic Load Nutrient Content vs. GI Fructose (lower GI) shown to increase insulin resistance Shape of Curve (ie. Orange Juice, rapid absorption) Add 30 to GI calculations which use white bread to compare to glucose scale.

15. Websites http://www.mendosa.com/gi.htm www.glycemicindex.com