glycemic index and Glycemic load

The presentation in detail covers the Glycemic index and glycemic load of various kinds of food. The standard calculation of Glycemic index and GLycemic load.
Moreover, it covers the food processing effects that can alter the glycemic load and glycemic index like gelatinization, retrogradation, cooking, annealing, etc.

1. Glycemic Index & Glycemic Load

2. GLYCEMIC INDEX GLYCEMIC LOAD FACTORS INFLUENCING GLYCEMIC INDEX HEALTH EFFECTS OF GLYCEMIC INDEX CONTENTS

3. GLYCEMIC INDEX GLYCEMIC LOAD FACTORS INFLUENCING GLYCEMIC INDEX HEALTH EFFECTS OF GLYCEMIC INDEX Introduction Std. Method Calc Glycemic Rank Second Meal Effect

4. INTRODUCTION The glycaemic index (GI) concept was introduced by Jenkins et al. in 1981 Carbohydrates should constitute 50-60 percent of the energy intake Glycemic Index is a measurement used to classify foods according to their potential for raising blood glucose levels. Only foods and beverages that contain carbohydrates are ranked, since they have the biggest effect on blood sugar. GI is defined as the incremental blood glucose area (0-2 h) following ingestion of 50 g of available carbohydrates in the test product as a percentage of the corresponding area following an equivalent amount of carbohydrate from a reference product.

5. GLYCEMIC INDEX The GI concept should be applied only to foods providing at least 15 g and preferably 20 g of available carbohydrates per normal serving Comparisons should be kept within the same food group Between those digested and absorbed in the small intestine, providing carbohydrate to body cells (available carbohydrates, ‘‘glycaemic carbohydrates’’), Alpha linkages which can be broken and those passing to the large intestine, providing substrate for the colonic microflora, i.e. dietary fibre Beta linkages which cannot be broken

6. The glycaemic response to a food, which in turn affects the insulin response, depends on the rate of gastric emptying , as well as on the rate of digestion and absorption of carbohydrates from the small intestine ‘‘Slow carbohydrates’’ have often also been considered advantageous for healthy people to avoid an excessive insulin response and hypoglycaemia between meals ‘‘Complex carbohydrates’’, i.e. starch, were ‘‘slow carbohydrates’’, whereas sugars (mono- and disaccharides) were considered ‘‘rapid’’

7. Classification of Starch for GI In vitro studies are designed to simulate digestion in the small intestine and measure the rate of starch digestion as an alternative to in vivo testing of the glycemic response to carbohydrate foods Classifications of Starch Rapidly digestible starch (RDS): RDS consists mainly of amorphous and dispersed starch, found in high amounts in starchy foods cooked by moist heat Slowly digestible starch (SDS): SDS is expected to be completely digested in the small intestine, but for one reason or another, it is digested more slowly Resistant starch (RS): RS is indigestible by body enzymes. In an in vitro method, the physico -chemical properties of a carbohydrate food are described by measuring the rate and extent of glucose release by enzymatic digestion under controlled conditions

8. Choosing Subjects Test time and prerequisite Determination of Glycemic carbohydrate Test Dosage Blood Sampling Reference Sample : White Bread or Glucose Typically 2 hr incremental area is calculated, but 3 hr may be also be calculated in case of extreme late characteristics Standard Method for GI Calculation 1 2 3 4

9. Standard curve of Glucose or white bread New curve read as % of standard curve Different research groups have used somewhat different blood sampling techniques ( venous or capillary ), times for calculating the glucose response area ( 1.5 - 3 h ) and reference product (glucose or white bread). The definition and methodology described in a recent FAO/WHO expert report , however, is now referred to as an international standard . Calculation of incremental area under the postprandial glucose IAUC sample IAUC standard *100

10. Key Low Medium High Glycemic Index 55 or less 56 -69 70 or higher Examples 100% stone- ground whole wheat or pumpernickel bread Most fruits, Whole wheat Quick oats Brown wild or basmati rice, White bread or bagel Corn flakes, Puffed rice, br an flakes, S hort-g r a i n white rice GLYCEMIC RANK Given the definition of GI, the concept is useful only for foods that provide substantial amounts of available carbohydrates. GI values for low carbohydrate foods, e.g. vegetables or foods mainly containing fat and protein, are difficult to determine and may be misleading when used in practice . It is suggested, therefore, that the GI concept is applied only to foods providing at least 15 g and preferably 20 g glycaemic carbohydrates per portion, i.e. products such as bread, cereals, pasta, rice and potatoes Fructose < lactose (glucose/ galactose) < sucrose (glucose/fructose) < glucose

11. THE SECOND MEAL EFFECT Breakfast to lunch / Low-GI breakfast attenuates the glycaemic response at lunch in both healthy and diabetic subjects Some low-GI foods give a prolonged insulinaemic response, providing sustained, slightly elevated insulin levels at the time of the next meal (lunch) This may improve peripheral glucose uptake, i.e. glucose tolerance, as well as removal of circulating lipoproteins The glycaemic response to the same food or meal may be influenced by the time, composition and GI of a previous meal . A prolonged glucose response after a breakfast meal has been demonstrated to improve glucose tolerance at lunch, denoted as the ‘‘second meal effect’’

12. Overnight effects / A late evening meal with slowly digested starch improves glucose tolerance at breakfast in type 2 diabetic patients In healthy individuals a similar effect was seen after an evening meal with low GI and rich in dietary fibre Colonic fermentation of dietary fibre, resulting in elevated serum levels of short-chain fatty acids, may reduce serum-free fatty acids and hepatic glucose output GI AND EXERCISE PERFORMANCE Pre-exercise meal / Low-GI foods ingested prior to exercise may contribute to enhanced performance High-GI foods ingested 30-60 min prior to exercise may cause hyperinsulinaemia and hypoglycaemia and have therefore been suggested to contribute to impaired performance The GI of a pre-exercise meal has been found to be of less importance if CHO are ingested during exercise

13. GLYCEMIC INDEX GLYCEMIC LOAD FACTORS INFLUENCING GLYCEMIC INDEX HEALTH EFFECTS OF GLYCEMIC INDEX Introduction Std. Method Calc GI Vs. GL Classification

14. GLYCEMIC LOAD: INTRODUCTION In practice, the actual carbohydrate load from a normal portion size varies considerably between food products The glycemic load (GL) is an equation that takes into account the planned portion size of a food as well as the glycemic index of that food. GL allows comparisons of the likely glycaemic effect of realistic portions of different foods, calculated as the amount of carbohydrate in one serving times the GI of the food (i.e. GL/g carbohydrate/GI/100) For example, spaghetti has a lower GI than boiled potatoes , but normal portion sizes of spaghetti are commonly larger than portions of potatoes . In theory, a large amount of a low GI food may increase your blood sugar as much as a small amount of a high GI food

15. Glycemic Load : GI * net grams of planned carbohydrate 100 (net carbohydrate is the total grams of carbohydrate minus the dietary fiber) GL may or may not differ between these two carbohydrate sources , depending on the applicable GI values and portion sizes The concept of glycaemic load (GL) was introduced, representing both the quality and the quantity of the carbohydrates in a food or a meal

16. Medium GL, Medium GI Low GL, High GI High GL, High GI

17. GLYCEMIC INDEX Vs. GLYCEMIC LOAD 100 mL 11g sugar GL= (58*11)/100 GL= 6.4 330 mL 37g sugar GL= (58*37)/100 GL= 21.5 600 mL 67g sugar GL= (58*67)/100 GL= 38.9 The product may be the same but not its GL but ALWAYS GI will be GI = 58

18. WHY IS GLYCEMIC LOAD IMP… !!

19. GLYCEMIC INDEX GLYCEMIC LOAD FACTORS INFLUENCING GLYCEMIC INDEX Various effects food processing operations HEALTH EFFECTS OF GLYCEMIC INDEX

20. FACTORS INFLUENCING GI RANKING

21. FACTORS INFLUENCING GI RANKING Molecules form tight clumps Slower rate of digestion Molecules are more open Faster rate of digestion Amylose Absorbs less water A m ylopect i n Absorbs more water 1. Type of Starch

22. 2. Physical Entrapment Endosperm Bran Germ Bran acts as a physical barrier that slows down enzymatic activity on the internal starch layer. Lower GI Pumpernickel bread (50) Higher GI Bagel (72) E.g. Mashed potatoes containing 1, 2 or 3% levels of high-viscosity hydroxypropylmethylcellulose , a modified cellulose dietary fiber and observed significant reduction in glycemic responses in all samples than the standard mashed potato

23. Digestible starch can be embedded between Resistant starch, hence taking more time to digest Alpha Bond Beta Bond

24. 3. Viscosity of Fiber Lower GI Apple (40) Higher GI Cheerios (74) Viscous, soluble fibers transform intestinal contents into gel-like matter that slows down enzymatic activity on starch. A portion of dietary fiber is fermented to volatile fatty acids in the gastrointestinal tract. The addition of viscous dietary fiber to a carbohydrate meal may reduce the glycemic response By forming viscous solutions, soluble fiber delays the rate of gastric emptying, reduces the mixing and diffusion in the small intestinal lumen, and thus reduces the rate of digestion and glucose absorption by the intestine

25. 4. Fat & Protein Content Lipids in potato may also affect the digestibility of starch by the formation of a complex of lipid with amylose. Amylose–lipid can be formed in the presence of both endogenous and added lipids during food processing. Contradictory conclusions were reached by researchers on the effect of complex formation on the digestibility of starch There are two types of amylose–lipid complexes : complex I and complex II. Complex I melts just below 100 °C in the DSC and exhibits little crystalline structure, whereas complex II exhibits a melting temperature well above 100 °C and consists of more crystallites The more complete crystal structure of complex II possibly renders it less susceptible to enzymatic degradation.

26. ICE CREAM ALWAYS ASK WHY ? Low GL, Low GI Fat and protein may influence gastric emptying and insulin secretion, but effects on GI Although addition of fat and protein to a meal containing carbohydrates may result in a lower glucose response, the relative difference between starch-rich foods with different GI values remains

27. DEGREE OF COOKING GLYCEMIC INDEX MASHED, PUREED, GI:87 to 101 , 78 and 70% of digestible starch BOILED, GI:59 to 70 BOILED + EATEN WITH SKIN BOILED AND LEFT AT ROOM TEMP. FOR SEVERAL HOURS RAW, least digestible starch (10%) 5. EFFECT of COOKING Low Medium High

28. 6. ANNEALING Heating starches above their gelatinization temperature results in the simultaneous loss of granular, lamellar, crystalline and double helical order. Heating at sub-gelatinization temperatures preserves granular structures, while other levels of organization are affected ANN is performed on starch granules in excess (60% w/w) or at intermediate water content (40% w/w) and held at a temperature above the glass transition temperature ( Tg ) but below the onset (To) temperature of gelatinization for a set period of time ANN can modify starches by narrowing of the gelatinization temperature range , increasing gelatinization temperatures, increasing granule stability, crystalline perfection , decreasing granular swelling, starch chain interactions within the amorphous and crystalline domains of the granule, formation of double helices.

29. ANNEALING

30. HMT is also a physical modification technique that involves the treatment of starch granules at low moisture levels (35% moisture w/w) for a certain time period (15 min–16 h) and at temperatures (84–120 °C) above Tg but below the gelatinization temperature HMT also increases gelatinization temperatures, widens the gelatinization temperature range , decrease granular swelling and amylose leaching, and increase in thermal stability in all starches HMT reduced the gelatinization endotherms and lowered total crystallinity of potato starch showed that the hydrothermal treatment (50% moisture at 55 °C for 12 h) of sweet potato starch increased the SDS level from 15.6% to 31.0%. HMT was done at 30% moisture at 100 and 120 °C for 2 h. The same investigated and observed that amylopectin structure and interactions formed during ANN and HMT had a significant impact on RDS, SDS, RS and expected GI levels of starches 7. HYDROTHERMAL

31. 8. EXTRUSION PROCESSING During extrusion the grain can be fragmented due to shear or can also be embedded in the protein fat matrix Upon heating and shearing during the extrusion process, the starch granules are fragmented, the granular crystallinity is decreased and partial depolymerisation occurs , which result in a uniform viscous starch fluid which can be described as a concentrated suspension of fractured granules embedded in a continuous and deformable matrix Extrusion processing conditions of temperatures, moisture addition (starch to water ratio) and screw speed, among others, will affect the changes in starch physical and chemical structure, and subsequently the GIs of the final extruded products. 1 2

32. 9. GELATINIZATION & RETROGRADATION Due to the high temperatures and pressures applied during the process, extrusion cooking makes starch granules in potato more damaged and gelatinized , thus more digestible than conventional-cooking methods such as boiling or baking Investigated on invitro digestibility and glycemic response of isolated potato starch in relation to granular size and degree of gelatinization and observed that the degree of gelatinization of starch strongly affects its digestibility in vitro and influences postprandial glycemic response. Extrusion conditions that increase barrel temperature, shear and pressure tends to enhance the degree of gelatinization An increase in resistant starch content in extruded products can also be promoted by retrogradation

33. Cold storage of potatoes has been demonstrated to affect the starch bioavailability in observed that the consumption of hot red potatoes (GI = 89) released more blood (40%) glucose than that of cold red potatoes (GI = 56) and pre-cooked, frozen and reheated before consumption, French fries gave less GI value than when consumed immediately after cooking So precooking and reheating potatoes before consumption will produce a smaller glycemic response compared with potatoes consumed immediately after cooking also suggested that recurrent heating and cooling result in more resistant starch that directly impacts the glycemic response by slowing digestion and absorption. With cooling or storing of potatoes for 24 h, the quantity of initial resistant starch (1.18%) in boiled potatoes increased to 4.63%. Cooling the outer portion of French fries also affected the overall resistant starch. Resistant starch observed in the whole sample of French fries (5.16%) was more than the resistant starch (1.17%) in the internal part only For example, 7% resistance starch in cooked potato increases to about 13% upon cooling . Therefore, cooling boiled potatoes forms resistance starch that is not digested in the small intestine and does not contribute to blood glucose response. 10. EFFECT of COLD STORAGE ON GI

34. WHAT ARE THE LIMITATIONS OF G I ? GI values were determined in studies where volunteers ate portions containing 50 grams of carbohydrate of each test food. 50 grams of carbohydrate from popcorn is ten cups popped , while from white rice is about one cup cooked. There is a wide variation in values assigned to the same food depending on reference source . GI values can vary depending on many factors GI values measured the effect of a test food when that food was eaten alone. The effect of food on blood sugar can vary from person to person . A lower GI value does not necessarily mean the food is a better choice . E.g a chocolate candy bar vs. 1 cup of brown rice have equal GI

35. GLYCEMIC INDEX GLYCEMIC LOAD FACTORS INFLUENCING GLYCEMIC INDEX HEALTH EFFECTS OF GLYCEMIC INDEX

36. A – ve relation between glycemic index and HDL cholesterol, was surveyed by the third National Health and Nutrition Examination Survey database and a British study. A sedentary lifestyle with a high glycemic - index diet increased risk relative to a sedentary lifestyle with a low dietary glycemic index or relative to an active lifestyle with a high dietary glycemic index. The Iowa Women’s Health Study, showed no significant association between glycemic index or load and diabetes An Italian case control study reported that the dietary glycemic index was related to colorectal cancer risk , ie , the higher the glycemic index, the greater the risk of colorectal cancer. Low GI reduces cholesterol levels, reduces weight, decreases type 2 diabetes risk, lowers blood glucose levels GI on HEALTH CONDITIONS

37. Pictures of Low/High GI Meals & Snacks GI = 60 GL = 48 GI = 42 GL = 31

38. Pictures of Low/High GI Meals & Snacks GI = 85 GL = 48 GI = 39 GL = 22

39. Meats and fats do have a GI ?  Yes  No