Determination of the glycaemic index of three types of Albany Superior bread

Abstract

English: The glycaemic index (GI) concept was introduced as a means of classifying different sources of carbohydrates (CHO) and CHO-rich foods in the diet, according to their effect on postprandial glycaemia since different carbohydrate containing foods have different effects on blood glucose responses. The GI is defined as the incremental area under the blood glucose response curve of a 50 g glycaemic (available) carbohydrate portion of a test food expressed as a percentage of the response to the same amount of glycaemic CHO from a standard food taken by the same subject. Though not the only factor that will determine whether the food should be included in the diet or not, the GI can be used alongside current dietary guidelines like the Food Based Dietary Guidelines and exchange lists to guide consumers in choosing a particular food with a predicted known effect on blood glucose levels and homeostasis. Variation in the GI values for apparently similar foods may reflect both methodologic factors as well as true differences in the physical and chemical characteristics of the specific food. Differences in GI values of similar foods could also be due to inherent botanical differences from country to country. Two similar foods may also have different ingredients, different processing methods or different degree of gelatinisation resulting in significant variation in the rate of CHO digestion and consequently the GI value. Methodological variables which include food-portion size, the method of blood sampling, sample size and subject characteristics, standard food, available CHO, volume and type of drinks consumed with test meals can markedly affect the interpretation of the glycaemic responses and the GI value obtained. Tiger Brands commissioned an independent assessment of the GIs of three Albany Superior™ breads namely Best of Both™, Brown™ and Whole Wheat™ bread carried out under strictly standardised conditions using methods complying with the most recent internationally accepted methodology. Methods Twenty healthy, fasting male volunteers, aged 18-27 years, each randomly consumed six different test meals consisting of 50 g available carbohydrates from three different test foods (three types of Albany Superior breads) and one type of standard food (glucose) (repeated three times in each subject) according to a Latin square design. Finger-prick capillary blood was collected fasting and within 10-15 min after the first bite was taken for every 15 min time interval for the first hour and thereafter for every 30 min time interval for the second hour, using One Touch Ultra™ test strips and One Touch Ultra™ glucometers (Lifescan™). The AUC and GI for the three different breads, were calculated using the mean of the three glucose responses (standard meals) as standard. Statistically significant differences were also determined. Results The mean GIs were 78.44, 72.01 and 79.62 for Whole Wheat™, Brown™ and Best of Both™ bread respectively. No statistically significant differences were found between the GIs of the three different Albany Superior™ breads. Conclusions From the study it can be concluded that the three different Albany Superior™ breads fell between the intermediate and high categories. Recommendations It is recommended that the methodological guidelines determined by the GI Task Force should be followed. It is also important to inform patients and consumers that in using the GI to choose CHO foods it is a fact that physiological responses to a food may vary between individuals and that it is normal for a specific food to have a high GI in some individuals and a medium or even a low GI in others. For labeling purposes it is recommended that the GI is presented as a mean with 95% confidence intervals.

Afrikaans: Inleiding Die glukemiese indeks (GI) -beginsel is in gebruik geneem ten einde verskillende bronne van koolhidrate en koolhidraatryke voedsel te klassifiseer volgens hul effek op post-prandiale bloedglukose aangesien verskillende koolhidraat-bevattende voedsel verskillende effekte het op bloedglukose reaksies. Die GI word gedefinieer as die inkrementele area onder die bloedglukoseresponskurwe vir ‘n toetsvoedsel wat ‘n 50 g glukemiese (beskikbare) koolhidraatporsie bevat, in verhouding tot (uitgedruk as persentasie) die ooreenstemmende area onder die kurwe nadat dieselfde koolhidraatporsie van ‘n standaardvoedsel deur dieselfde persoon ingeneem is. Alhoewel die GI nie die enigste faktor is wat bepaal of ‘n voedselsoort in die dieet ingesluit moet word of nie, kan die GI met huidige dieetriglyne bv. die “Food Based Dietary Guidelines” en Ruillyssisteem geïntegreer word om sodoende verbruikers by te staan in hul keuse van voedsel met ‘n bekende geskatte effek op bloedglukosevlakke en homeostase. Variasie in die GI vir skynbaar soortgelyke voedsel kan beide metodologiese faktore asook werklike verskille in die fisiese en chemiese kenmerke van spesifieke voedsel reflekteer. Verskille in GIwaardes van soortgelyke voedsel kan moontlik toegeskryf word aan verskille in botaniese kenmerke eie aan ‘n spesifieke land. Twee soortgelyke voedsels kan moontlik ook verskil wat betref bestanddele, prosseseringsmetode en graad van gelatinisasie wat tot variasie in die tempo van CHOvertering en dus gevolglik die GI-waarde kan lei. Metodologiese veranderlikes wat insluit voedselporsiegrootte, die metode van bloedinsameling, steekproefgrootte en proefpersoonkenmerke, standaardvoedsel, beskikbare CHO, volume en tipe vloeistof wat tydens toetsmaal ingeneem word, kan die interpretasie van glukemiese response en die GI waarde wat verkry word noemenswaardig beïnvloed. ‘n Voedselmaatskappy het opdrag gegee dat ‘n onafhanklike bepaling van die GIs van drie Albany Superior™ brode naamlik “Best of Both™”, “Brown™” en “Whole Wheat™” gedoen word, onder streng gestandaardiseerde toestande deur gebruik van mees onlangse internasionaal aanvaarbare metodologie. Metodes ‘n Groep van 20 gesonde, vastende manlike vrywilligers, 18-27 jaar oud, het elk ewekansig 50 g beskikbare koolhidrate vanaf drie verskillende toetsvoedsels (drie tipes Albany Superior brode) en een tipe standaardvoedsel naamlik glukose wat drie keer herhaal is in elke proefpersoon, in ses verskillende toetsmaaltye ingeneem, volgens ‘n Latynse vierkantontwerp. Kapillêre bloed, d.m.v. vingerprik, deur gebruik te maak van One Touch Ultra™ toetsstrokies en One Touch Ultra™ glukosemeters (Lifescan™), is versamel vastend, binne 10-15 min nadat die toetsmaal ‘n aanvang geneem het vir elke 15 min tydsinterval van die eerste uur en daarna vir elke 30 min tydsinterval van die daaropvolgende uur. Die area onder die kurwe (AUC) en GI vir die drie verskillende brode, is bereken deur die gemiddeld van die drie glukose response (standaardvoedsel) as standaard te gebruik. Statisties betekenisvolle verskille is ook bepaal. Resultate Die gemiddelde GIs was respektiewelik 78.44, 72.01 and 79.62 vir “Whole Wheat™”, “Brown™” and “Best of Both™” brood. Geen statisties betekenisvolle verskille is tussen die GIs van die drie verskillende Albany Superior™ brode gevind nie. Gevolgtrekkings Die gevolgtrekking kan uit die studie gemaak word dat die GIs van drie verskillende Albany Superior™ brode tussen die intermediêre tot hoë GI kategorieë val. Aanbevelings Dit word aanbeveel dat die metodologiese riglyne soos opgestel deur die GI Werksgroep gevolg moet word. In die gebruik van die GI om koolhidraatvoedsel te kies, moet pasiënte en verbruikers bewus gemaak word van die feit dat fisiologiese response tot ‘n voedsel tussen individue mag varieer en dat dit normaal is vir ‘n spesifieke voedsel om tot ‘n hoë GI in sommige individue en tot ‘n medium of selfs lae GI in ander, aanleiding te gee. Die aanbeveling word gemaak dat die GI vir etiketteringsdoeleindes, as ‘n gemiddeld met ‘n 95% vertrouensinterval voorgestel word.