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Starchy Foods andGlycemic Index
David J.A. Jenkins, MD, PhDThomas M.S. Wolever, MD,
PhDAlexandra L. Jenkins, RD
Different starchy foods produce different glycemicresponses when fed individually, and there is someevidence that this also applies in the context of themixed meal. A major reason appears to relate to therate at which the foods are digested and the factorsinfluencing this. A similar ranking in terms of glycemicresponse to specific foods is seen independent of thecarbohydrate tolerance status of the groups tested.Potentially clinically useful starchy foods producingrelatively flat glycemic responses have been identified.Many of these are considered ethnic or traditional andinclude legumes; pasta; grains such as barley, parboiledrice, and bulgur (cracked wheat); and whole-grainbreads such as pumpernickel. Specific incorporationof these foods into diets has been associated withreductions in low-density lipoprotein cholesterol andtriglyceride levels in hyperlipidemia and with improvedblood glucose control in insulin-dependent diabeticpatients. To facilitate identification of such foods, it hasbeen suggested that the glycemic response should beindexed to a standard (e.g., white bread) to allowcomparisons to be made between the glycemic index offoods tested in different groups of subjects. The scopeof application of this principle is subject to furtherinvestigation. It may be used to expand the range ofpossibly useful starchy foods for trial in the diets ofdiabetic patients. Diabetes Care 11:149-59, 1988
Different carbohydrate foods produce differentglycemic responses despite an apparent lackof difference in macronutrient composition(1,2). The classification of carbohydrate foods
was first put on a systematic basis by Otto and col-leagues (3,4), who, after testing foods, allowed carbo-hydrate incorporation into the diabetic diet in propor-tion to the glycemic response they produced. In this way
the glycemic impact of the diet could be kept constantregardless of the variety of carbohydrate foods used (3,4).
Later studies by Crapo and colleagues (5-8) focusedon the differences between starchy foods of similar mac-ronutrient composition. Differences in both glucose andinsulin responses were observed, and it was postulatedthat possible differences in rates of digestion of the foodswere responsible. These differences in rates of digestionof starchy foods were subsequently confirmed (Fig. 1)and related to the glycemic responses observed in bothnormal and diabetic individuals (9,10).
From the beginning of the 1980s, many tests of singlefoods (11-28) and mixed meals (24,29-35) have beenundertaken in both normal and diabetic subjects. How-ever, because of a lack of standardization of methodsof data presentation, the results of different studies werenot always directly comparable. In 1981, the conceptof the glycemic index (Gl) was proposed as a methodof assessing and classifying the glycemic response tocarbohydrate foods (11). It was hoped that this wouldallow foods to be compared more readily. It would alsoallow the experience of different investigators to bepooled by indexing the foods tested to a common stan-dard. Initially, glucose was used, but this proved to beless acceptable for routine use than white bread of knowncomposition. The Gl was therefore defined as
incremental blood glucose area after food
corresponding area after equicarbohydrate portion of white breadx 100
From the Department of Nutritional Sciences, Faculty of Medicine, and theDivision of Endocrinology and Metabolism, St. Michael's Hospital, Universityof Toronto, Toronto, Ontario, Canada.
Address correspondence and reprint requests to David J. A. Jenkins, Depart-ment of Nutritional Sciences, Faculty of Medicine, University of Toronto, To-ronto, Ontario M5S 1A8, Canada.
DIABETES CARE, VOL. 11, NO. 2, FEBRUARY 1988 149
GLYCEMIC INDEX
.E 0
^ 7—
•̂ EE E 5
W n 4
O ^ui32-5 2
bo
hyd
lysa
te
o.2 0
^ ^ * Wholemeal Bread
/ Miolcn-
y ^ ^^^ l -T l t e
y' / ^^^^Nuic t
/ ^ ^ S ^ , Wliolen
^^ y^^/yr ^ ^ ^ ^ ^ ^ Porrid
SpaghettiRice
Potato
eal Spaghetti
p.c Oats
fat Peas
1 2 3 4Time (hours)
FIG. 1. Increase in concentration over 5h of products of starch digestion, mea-sured as glucose after acid hydrolysis,subsequent to incubation of 2 g availablecarbohydrate portions of foods withpooled human saliva and pancreaticjuice.
By applying this approach to data from different groupsof subjects and different centers (12), it has been pos-sible to begin to classify a substantial number of foodsin terms of their glycemic responses (Table 1).
Foods that have been shown to have low glycemicresponses include whole-grain (as opposed to wholemeal) cereals (15), pasta (17,36), and legumes (13,21,37).It was suggested that inclusion of such foods in the dietsof patients with diabetes might aid dietary managementby improving diabetes control.
OBJECTIONS TO GLYCEMIC INDEX
Objections to the Gl concept were raised early (38) andhave not been resolved (34,39). These objections haveresulted in a statement from the recent NIH consensusconference on diet and exercise in non-insulin-depen-dent diabetes (NIDDM) that recommended against theuse of Gl in the dietary management of diabetes (40).The concern revolves around 3 major issues: 7) largeindividual variation in responses, 2) lack of agreementamong different centers, and 3) lack of difference be-tween mixed meals. In addition, it has been pointed outthat there are no studies showing long-term benefits oflow-GI foods (38,40). For these reasons it has beenmaintained that the Gl has no clinical utility (34,38-40).Individual variation in glycemic responses. There arelarge differences among individuals with respect to theabsolute level of blood glucose achieved after meals.Factors that have been suggested to influence this in-clude the presence and type of diabetes (38,41,42), age,sex, body weight, and race (40). It has therefore beenstated that glycemic responses to foods should be testedin the specific group for which recommendations are
made (38). However, when considering the relative gly-cemic effects of different foods, i.e., the glycemic index,there is in fact some evidence for agreement amongdifferent groups (Table 1).
Early studies with four starchy foods (bread, potato,rice, and corn) demonstrated the same order of rankingof the glycemic and insulin responses when these foodswere tested in nondiabetic compared with diabetic vol-unteers (6,8). Since then, several studies have shownsimilarities in the ranking of responses to a wide rangeof foods tested in nondiabetic, NIDDM (13), and insu-lin-dependent diabetic (IDDM; 15-1 7) subjects. On theother hand, many studies do not agree (Table 1).
More recently, it has been maintained that consider-ation of average glycemic responses is inadequate be-cause they may conceal large differences in response indifferent individuals (39). This objection would be ofmajor clinical importance if the variability in responsebetween patients was such that certain individuals con-sistently failed to show the expected differences in gly-cemic responses between foods. The prescription of adiet containing foods of lower Gl would certainly notresult in lower postprandial blood glucose responsesthroughout the day. Unless these individuals could bereadily identified, the clinical application of Gl datawould indeed be limited and inappropriate if the num-ber of patients who failed to show a consistent responsewas large. In view of the substantial coefficient of vari-ation often seen in the GI to single foods, this negativeoutcome is a real possibility.
We have therefore examined the individual data thatformed the basis for recently published papers. In thesestudies several low-GI foods were taken by different di-abetic patients (Table 2; 15,16). Such a range of foodsmight be exchanged for foods of higher Gl in the dietsof diabetic patients. We therefore considered it clinicallyrelevant to determine whether the overall response to
150 DIABETES CARE, VOL. 11, NO. 2, FEBRUARY 1988
D.J.A. JENKINS, T.M.S. WOLEVER, AND A.L JENKINS
TABLE 1Mean glycemic index (Gl) values of foods adjusted proportionately so that Gl of white bread = 100
Food Gl values* Subjectst Mean Gi
BreadsRye
Crispbread 90", 100 C,A 95Whole meal 89 G 89Whole grain, i.e., pumpernickel 58", 78a C,G 68
WheatWhite 100 (defined) A-K,M 100Whole meal 93", 96, 100, 104, 106 C,G,B,A,J 100 ± 2
PastaMacaroni
White, boiled 5 min 64" I 64Spaghetti
Brown, boiled 15 minWhite, boiled 15 minWhite, boiled 5 minProtein enriched
Star pastaWhite, boiled 5 min
Cereal grainsBarley (pearled)BuckwheatBulgurMillet
RiceBrown
Instant, boiled 1 minInstant, boiled 6 minPolished, boiled 5 minPolished, boiled 15 minParboiled, boiled 5 minParboiled, boiled 25 min
Rye kernelsSweet cornWheat kernels
Breakfast cerealsAll BranCornflakesMuesliPorridge oatsPuffed riceShredded wheatWeetabix
CookiesDigestiveOatmealRich teaPlain crackers (water biscuits)
Root vegetablesPotato
InstantMashedNew, boiledRussett, bakedSweet
YamLegumes
Baked beans (canned)Bengal gram dalButter beans
DIABETES CARE, VOL. 11, NO. 2, FEBRUARY 1988 151
61"46", 59", 68", 72C
45"38b
54"
31C
7465C
103
65", 9665"121"58C
68-, 70", 73", 78a, 83", 10454C
58", 66", 72C, 78"47C
66C, 67" 85", 86, 87, 9063C
71", 74a, 76"107", 116, 121"
9671a, 88", 93, 96
132"97109
77, 86788091
116, 119"100
67", 75, 78", 101112, 134~, 137a
70a
74
60c
7C, 16C
39C, 52C
AI,B,C,A
II
I
FAGA
N,AHLH
M,L,C,B,H,AH
D,H,E,RG
E,L,R,A,J,DG
B,A,NL,A,B
AA,C,K,B
LAA
B,AAAA
A,LJ
C,B,L,AE,R,DAA
AJ,MJ,A
6161 ± 6"
4538
54
317465103
816512158
79 ± 5"54
65 ± 4J
4780 ± 4"
63
74 ± 1b
115 ± 496
87 ± 613297109
82788091
118100
80 ± 7128 ± 8
7074
601246
GLYCEMIC INDEX
TABLE 1(Continued)
Food Gl Values* Subjectst Mean G
Legumes (Continued)Chick peas 46% 52C B,A 49Green peas
DriedFrozen
Haricot (white) beansKidney beansRed lentilsPeanutsSoy beans
DriedCanned
FruitAppleBananaOrangeOrange juice
SugarsFructoseGlucose
HoneyMaltoseSucrose
Snack foodsCorn chipsPotato chips
Dairy productsIce creamSkim milkWhole milkYogurt
individual mean values from different groups of subjects. For significant difference from white bread (Gl = 100): aP < .05; bP < .01; CP <.001; "significance not given and unable to be calculated.tSubjects (refs.): A, normal English (11); B, predominantly NIDDM Canadian (13); C, diabetic German (4); D, normal American (6); E, NIDDMAmerican (8); F, NIDDM Canadian (14); G, NIDDM and IDDM Canadian (20); H, NIDDM and IDDM Canadian (15); I, NIDDM and IDDMCanadian (16); J, normal rural African (18); K, NIDDM Canadian (19); L, normal Australian (20); M, normal Indian (21); N, normal American(22); O, normal Canadian (23); P, NIDDM Canadian (24); Q, IDDM Canadian (24); R, impaired GTT (7); S, normal Canadian (25).^Significant difference from 100 given where >3 mean values are available.
these foods was consistent for each individual (i.e., for those foods, we believe the Gl concept can be ap-whether for each patient the mean value for the low-GI plied to individual diets composed of many foods,foods was significantly below that of bread, a higher Gl Lack of agreement between different centers. Dis-food). For each subject, the mean Gl of the foods was similarities have been observed between the glycemicsignificantly below that of bread despite the wide vari- responses to certain foods tested in different centers,ation in individual responses to a given food. It cannot notably potato and rice (5-8,11,13). However, closerbe inferred from these data whether certain individuals examination of the foods reveals that the center withconsistently show lesser changes in Gl than others. It is the consistently higher glycemic response to potatoalso not apparent to what extent the differences from fed a 317-g baked russet potato (6,8), whereas the cen-the expected values are due to intraindividual variabil- ter with the consistently lower response fed a 273-g boiledity; i.e., had each individual repeated each test on sev- new potato (11,13). The difference in weight fed, dueeral occasions, the mean would probably more closely to the use of different food tables, accounts for part ofapproximate the expected Gl value (23; unpublished the difference in glycemic response. There may also beobservations). Nevertheless, because each diabetic vol- true but unidentified differences between the more pow-unteer demonstrated a mean Gl value for the foods tested dery russet potato and the glutinous new potato. Ex-that was similar to or below the predicted mean Gl value amination of the types of rice fed indicate that the center
152 DIABETES CARE, VOL. 11, NO. 2, FEBRUARY 1988
32", 68C
55", 74a
44% 45% 56% 8427% 42% 65b
25% 42% 43C
10% 19C
20c
22C
48", 57C
66", 81, 90, 9946% 58% 73"
67a
29% 30", 35b
122% 131, 132", 137%137", 141% 145% 158a
126152b
85", 86, 91, 92
99"74% 79"
52b
46C
4 9 c
52C
C,AC,A
O,A,P,QM,A,BS,A,BJ,A
AA
C,AC,B,A,JJ,A,CA
A,C,KE,K,R,C,D,J,A,M
AA
C,A,K,J
LA,L
AAAA
5065
57 ± 1045 ± 1137 ± 6b
15
2022
5384 ± 759 ± 8a
67
31 ± 2b
138 ± 4C
126152
89 ± 2b
9977
52464952
D.J.A. JENKINS, T.M.S. WOLEVER, AND A.L. JENKINS
with the lower response (5-8) fed parboiled rice, whereasthe higher result was obtained in a center that fed regularrice (11,13). Subsequent testing has demonstrated thatparboiled cereals, whether rice (16) or wheat (15), arenotable in resulting in relatively flat blood glucoseprofiles. Such differences are not simply due to lackof reproducibility but represent true differences inphysiologic effects between foods that previously wereconsidered the same. Other differences have also beenreported with respect to rice. Varieties of long-grain ricemay be higher in amylose starch and consequently givea flatter blood glucose response than the more amylo-pectin-rich short-grain varieties (44).
In addition, the ripeness of fruits will determine theirsugar content, a factor shown to be especially importantin the case of bananas (45). Cooking will enhance thedegree of gelatinization of starch (46) and hence thedegree to which it raises the blood glucose (47). Theseand many other food-related factors determining post-prandial glycemia and insulin response are emerging(48).
Substances such as phytates (49,50) and lectins (51)and indeed the dietary fiber content (52) are all knownto influence glycemic response and are altered by dif-ferent growing conditions (53). Finally, the absoluteamounts fed by different investigators may depend onthe food tables used or whether a direct analysis wasperformed. If so, the method used to determine dietaryfiber content will influence the available carbohydratecontent. To some, the field might appear to be too vari-able to allow meaningful interpretation. An alternativeview would be that much knowledge is being acquiredthat will change our perception of food systems but willallow predictions to be made based on knowledge ofphysiologic responses to foods. A surprising fact is that,despite all these unknowns, there is a broad measure ofagreement on the relative glycemic effect of many car-bohydrate foods tested in different centers (Table 1).Lack of difference between mixed meals. The mosttopical criticism of the Gl concept is that, when indi-vidual carbohydrate foods are taken as part of a mixed
mg/100 ml
300
250
200
150
100
50
0
=3
60 120
Time (min)
180
FIG. 2. Mean plasma glucose levels of 8 NIDDM subjectsfed standard test meals containing baked potato ( •—•) ,rice ( •—•) , spaghetti (O—O), or lentil (O—O) as majorsource of carbohydrate (34).
meal, differences in glycemic responses between thefoods are abolished. Several studies fail to show anydifference in glycemic response to mixed meals(33,34,54,55). With the first study to apply Gl in thissituation (Fig. 2), a major problem in interpretation wasthe use of total rather than incremental areas for com-parison of postprandial responses (56).
The suggestion that clinically there may be no greatadvantage from using the Gl to achieve a modest re-duction in postprandial glycemia when the fasting bloodglucose value is grossly elevated is uncontested. Theprimary concern must be the reduction of the fastingblood glucose level. However, if Gl is to be used torank the postprandial glucose responses to differentmeals, then the method of assessment would seem im-portant. The fasting blood glucose is not influenced bythe subsequent meal. However, if the total blood glu-cose area is chosen, a large variation in starting valuecould obscure differences between meal responses whenexpressed as absolute postprandial levels. The Gl clas-sification has therefore been based on incrementalresponses. Similar treatment should be given if Gl is tobe used to predict the mixed-meal response.
In addition, if absolute values are used to calculate
TABLE 2Variability of individual glycemic indexes (Gl) for 6 low-GI cereal foods compared with white bread testedin 8 diabetic patients
Food
BreadBulgurPumpernickelParboiled riceBarleyWheat kernelsRye kernelsMean ± SESignificance
vs. bread (P)
Gl
100657867316347
58.5 ± 6.8
<.01
1
100496952283631
44.2 ± 6.3
<.001
NIDDM patients
2
100557077314841
53.7 ± 7.1
<.OO5
3
100387957294727
46.2 ± 8.0
<.005
4
100709873165743
59.5 ±11.4
<.02
5
100825557489351
64.3 ± 7.6
<.01
IDDM patients
6
100637059305759
56.3 ± 5.6
<.001
7
100317664
74633
42.8 ± 10.1
<.005
8
100629049318176
64.8 ± 9.0
<.01
Mean ±
100.0 i56.0 i75.9 i61.0 i27.5 i58.2 i45.1 i53.9 i
<.001
SE
05.94.73.54.26.85.85.8
DIABETES CARE, VOL. 11, NO. 2, FEBRUARY 1988 153
GLYCEMIC INDEX
Gl, then the higher the fasting blood glucose value, thesmaller the contribution of the postprandial response tototal glycemia. This can be demonstrated by analyzingdata from a different study. Figure 3 illustrates both theabsolute (top) and incremental {bottom) glycemic re-sponses of 15 NIDDM subjects who ate meals of bread,rice, spaghetti, and barley to which the same amountof fat and protein as cheddar cheese had been added(57). The incremental areas for rice, spaghetti, and bar-ley were 23, 44, and 59% less, respectively, than thatfor bread, whereas the total areas for these meals wereonly 2, 19, and 25% less than that of bread. Thesereduced figures further diminished the chance of a re-lationship between the Gl for single foods and mixedmeals (39). Furthermore, we consider it important thatthe foods tested in a mixed meal should also have beentested singly before conclusions are drawn relating to
300
200
0)
o
Oo
100
0
200
100
0 1 2 3Time (hours)
FIG. 3. Mean blood glucose concentrations {top) and bloodglucose increments {bottom) of 15 NIDDM subjects fedtest meals containing 50 g carbohydrate from white bread(A), polished rice (O), spaghetti (•), or pearled barley (O).To each food, 32 g cheddar cheese and 100 g cooked to-mato were added (57).
the validity of applying the Gl in this situation. Wherethis has been done, a degree of predictability has beenfound (Fig. 4; 58).
There are at least five other published studies thathave examined the effects of mixed meals (32,33,35,59,60). Only two of these are generally quoted (39).In one, it was concluded that the glycemic responses tothe meals "were similar except for one meal" (33). Thedifferent meal (meal B) had a significantly greater gly-cemic response than two of the other meals (meals Aand C), as predicted by the Gl of meal B, and was 21and 27 Gl units greater than meals A and C (23). Inaddition, although Bantleetal. (32) concluded that fruc-tose-containing meals were not always lower than thosecontaining other carbohydrates, they were able to dem-onstrate a significant difference in NIDDM subjects (whoare less variable than IDDM subjects) (23). In a laterstudy by this group, small but significant differences be-tween meals of differing predicted glycemic effect werefound in normal subjects, but they were not seen inNIDDM subjects (54).
Three less-known studies show good predictive abilitywith Gl. Parillo et al. (59) found the expected differencebetween bread and spaghetti when incorporated into amixed meal (Fig. 5). Slama et al. (60,61) also found thatblood glucose and insulin responses for different foodsin a mixed meal ranked as expected. Finally, Collier etal. (35) fed five different mixed meals to NIDDM sub-jects (Fig. 6). These resulted in a range of differences ofalmost 100 mg/dl in postprandial blood glucose levels.The close correlation between the expected Gl of themeals and the observed glycemic responses was prob-ably a reflection of the fact that the foods fed had beentested previously and were known to have glycemic re-sponses equivalent to their published Gl values (Fig. 7).Therefore, before concluding that differences in gly-cemic response to individual foods are lost when theyare combined in a mixed meal, it appears important topretest the individual carbohydrate components of themixed meal.
EFFECTS OF DIETARY CHANGE
Only two studies have been published of the effect ofincorporating carbohydrate foods that cause relativelylow rises in blood glucose into the diet. In one, diabeticchildren reduced the glycemic impact of their diets for6 wk by eating carbohydrate foods known to raise bloodglucose minimally instead of more conventional car-bohydrate foods (67). This change resulted in improvedglucose tolerance and a fall in serum cholesterol after astandard meal. Although no significant fall was seen inHbA1c levels, there was a significant fall in glycosylatedalbumin, probably due to the much shorter half-life ofthis protein, which makes it a more suitable marker forrelatively short dietary studies (63). In the second studythe same dietary maneuver was undertaken by a groupof hypertriglyceridemic, predominately glucose-intol-
154 DIABETES CARE, VOL. 11, NO. 2, FEBRUARY 1988
D.J.A. JENKINS, T.M.S. WOLEVER, AND A.L. JENKINS
FIG. 4. Mean plasma glucose and insu-lin levels of NIDDM subjects fed test mealscontaining white beans processed in 2different ways: O, A, damaged cell walls;• , undamaged cell walls. Left panel, re-sponses to bean products fed alone. Rightpanel, responses when bean productswere consumed as part of mixed meal(58). *P < .05, **P < .01.
350
300
250
200
0
60
50
40
30
20
II 200
PLASMA INSULIN
30 60 120
TIME Imin)
180
erant individuals over 1-mo periods (14). This dietaryexchange was accompanied by falls in serum triglyc-eride and total and low-density lipoprotein cholesterollevels. In these studies, there were small to modest in-creases in dietary fiber, which seemed unlikely to pro-vide the whole explanation.
A Blood glucose(mmol/l)
• ' L.
0 30 60 90 120 150 180 210 240 270 300
Time (min)
FIG. 5. Mean ± SE blood glucose increments of 7 diabeticsubjects fed mixed meals containing white bread (O), newpotato (•), or spaghetti (•) as major carbohydrate source(59). *P < .05, **P < .025, ***P < .01 vs. spaghetti.
The conclusion is supported by some of the most suc-cessful dietary studies to show improvement in glucosecontrol in diabetic patients (64-69) or reductions in bloodlipids in hyperlipidemic individuals (66,70). Althoughthe thrust of such studies was to increase fiber intake, itwas achieved with foods with a lesser impact on bloodglucose than many of the foods they displaced. Dietary-fiber studies where this has not been the case have re-
Q
CD300
GOCD 200
(JD
CDCD—JPQ
100
0 1 2 3
TIME (HOURS)
FIG. 6. Mean blood glucose responses of 6 NIDDM sub-jects fed mixed meals containing instant potato (•), whitebread (A), polished rice (Q), white spaghetti (D), or mix-ture of red lentils and barley (O) as major carbohydratesource. Values that differ by >37 mg/dl are significantlydifferent. P < .05 (35).
DIABETES CARE, VOL. 11 , NO. 2, FEBRUARY 1988 155
GLYCEMIC INDEX
1OOO
UJ
UJ 500CO©
C5
20 40 60 80 100MEAL G.I.
FIG. 7. Correlation between mean incremental blood glu-cose response areas for meals illustrated in Fig. 6 withexpected meal glycemic index. P < .01, r = .9875.
suited in much lesser benefits (71-75), and the benefitsseen in lipid and carbohydrate metabolism may havebeen largely attributable to the accompanying reductionin the proportion of fat in the diet.
UNANSWERED QUESTIONS
The major question that still remains is: what clinicalgains can be expected through tighter control of post-prandial glycemic excursions? This can be resolved bydietary trials where low-GI foods are fed. However, ifthese trials are to be undertaken with the necessary de-gree of compliance, then an expanded list of classifiedfoods is required.
Gl studies have drawn attention to the agreement anddisagreement between investigators in terms of the bloodglucose responses observed after both single foods andmixed meals. The similarities provide hope that a systemof classification, if comprehensive, may be feasible, usefulas an adjunct to food tables in designing therapeuticdiets, and a stimulus to studies of mechanism. The dis-agreements indicate there is much more to learn in termsof processing and the effect of food components andfood form on physiological processes (e.g., digestion,transit time, endocrine responses) before the most effec-tive use can be made of the knowledge.
The Gl approach to classification has also highlightedthe urgent need for uniform food tables giving true avail-able or absorbable carbohydrate (starch and sugars) anddietary fiber separately so that known amounts of car-bohydrate are fed. Different portion sizes are used bydifferent investigators, and differences in results maysimply be due to the amounts of food fed.
APPLICATION OF GLYCEMIC INDEX
Strict application of Gl exchange principles is only pos-sible in a research setting, where the Gl of diets may becalculated (23,56). After standard dietary advice, thecontrol or "normal" diet for most diabetic and hyper-lipidemic patients has a Gl of 85-90 (14,63,76) (whitebread = 100). This may be reduced by a mean 11-13(14,62). These changes are not large numerically butrequire a considerable change in the nature of the car-bohydrate foods eaten (Fig. 8). Thus, lower-GI foodssuch as pumpernickel bread will be increased from vir-tually nonexistent levels, and regular wheat breads willbe substantially reduced (Fig. 8). Nevertheless, for thosenot in a research setting, it may be possible to make use
20
0
40
20
20
RYEBREAD
OATBRAN BULGUR BEANS BARLEY SPAGHETTI
POTATO RICEBREAKFAST
CEREALS
FRUIT
BAKEDGOODS SUCROSE
FIG. 8. Intakes of different carbohydrate foods expressedas proportion of total dietary carbohydrate. Open bars,control; solid bars, periods of low glycemic index (Gl).Upper panel, foods that increased during low Gl; middlepanel, foods that decreased during low Gl; lower panel,foods that remained unchanged during low Gl.
156 DIABETES CARE, VOL. 11 , NO. 2, FEBRUARY 1988
D.J.A. JENKINS, T.M.S. WOLEVER, AND A.L. JENKINS
of Gl data by selecting foods to incorporate into patients'diets that have the desired nutritional profile, complyingwith current guidelines, and yet have a lower glycemicimpact. Many of these are traditional or ethnic foods,e.g., pasta, lentils, beans, parboiled rice, barley, bulgur,and pumpernickel bread, which, rather than constrict-ing the patients' eating habits, may in effect introducethe patients to new foods.
Current recommendations by several agencies con-cerned with health (including heart foundations andcancer institutes in addition to diabetes associations)support the increased use of carbohydrate foods. Overthe last decade, the overall aim has been to reduce con-sumption of saturated fat, which is implicated in raisingserum cholesterol levels, and total dietary fat, which isassociated epidemiologically with colon and breast tu-mors. It has not been suggested that the increased car-bohydrate that replaces fat should come from sugars.Nevertheless sugar may not raise the blood glucosemore than many starchy foods (32), and fructose sub-stitution actually results in significantly flatter postpran-dial glucose responses (77). Therefore, modest amountsof sugars may be used as sweeteners. However, theiruse as a source of calories is still a matter of debate.There is concern that in susceptible individuals, fructosemay raise serum triglyceride levels (78,79). Further-more, when sucrose replaces starch in diets higher insaturated fats or very high in carbohydrate, it may in-crease the levels of both cholesterol and triglyceride(80,81). Thus, despite the fact that high fat or fructose-containing foods may cause relatively flat blood glucoseresponses, they cannot be recommended solely on thebasis of their lower acute glycemic response. The Glclassification may therefore be most appropriately usedto rank starchy foods. These starchy foods would alreadyhave been chosen for possible inclusion in the diet onthe basis of their nutritional attributes. In this setting theGl would allow selection of foods that have the addedadvantage of producing lower postprandial glycemic ex-cursions.
ACKNOWLEDGMENTS
These studies were supported by the National Sci-ences and Engineering Research Council, Canada.
REFERENCES
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2. Conn JW, Newburgh LH: The glycemic response to iso-glucogenic quantities of protein and carbohydrate. / ClinInvest 15:665-71, 1936
3. Otto H, Bleyer G, Pennartz M, Sabin G, Schauberger G,Spaethe K: Kohlenhydrataustausch nach biologischenaquivalenten. In Diatetik bei Diabetes Mellitus. Otto H,Spaethe R, Eds. Bern, Huber, 1973, p. 41-50
4. Otto H, Niklas L: Differences d'action sur la glycemied'aliments contenant des hydrates de carbone: conse-quences pour le traitment dietetique du diabete sucre.Med Hyg 38:3424-29, 1980
5. Crapo PA, Reaven G, Olefsky J: Plasma glucose and in-sulin responses to orally administered simple and com-plex carbohydrates. Diabetes 25:741-47, 1976
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14. Jenkins DJA, WoleverTMS, Kalmusky J, Giudici S, Gior-dano C, Wong GS, Bird JH, Patten R, Hall M, BuckleyGC, Little JA: Low glycemic index foods in the man-agement of hyperlipidemia. Am J Clin Nutr 42:604-17,1985
15. Jenkins DJA, Wolever TMS, Jenkins AL, Giordano C, Giu-dici S, Thompson LU, Kalmusky J, Josse RG, Wong GS:Low glycemic response to traditionally processed wheatand rye products: bulgur and pumpernickel bread. Am IClin Nutr 43:516-20, 1986
16. Wolever TMS, Jenkins DJA, Kalmusky J, Jenkins AL, Gior-dano C, Giudici S, Josse RG, Wong GS: Comparison ofregular and parboiled rices: explanation of discrepanciesbetween reported glycemic responses to rice. Nutr Res6:349-57, 1986
17. Wolever TMS, Jenkins DJA, Kalmusky J, Giordano C, Giu-dici S, Jenkins AL, Thompson LU, Wong GS, Josse RG:Glycemic response to pasta: effect of food form, cookingand protein enrichment. Diabetes Care 9:401-404, 1986
18. Walker ARP, Walker BR: Glycemic index of South Africanfoods determined in rural blacks—a population at lowrisk to diabetes. Hum Nutr Clin Nutr 36:215-22, 1984
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22. Potter JG, Coffman KP, Reid RL, Drall JM, Albrink MJ:Effect of test meals of varying dietary fiber content onplasma insulin and glucose response. Am j Clin Nutr34:328-34, 1981
23. Wolever TMS, Nuttall FQ, Lee R, Wong GS, Josse RG,Csima A, Jenkins DJA: Prediction of the relative bloodglucose response of mixed meals using the white breadglycemic index. Diabetes Care 8:418-28, 1985
24. Jenkins DJA, Wolever TMS, Wong GS, Kenshole A, JosseRG, Thompson LU, Lam KY: Glycemic responses to foods:possible differences between insulin-dependent and non-insulin-dependent diabetics. Am ) Clin Nutr 40:971-81,1984
25. Wolever TMS, Cohen Z, Thompson LU, Thorne MJ, Jen-kins MJA, Prokipchuk EJ, Jenkins DJA: Heal loss of avail-able carbohydrate in man: comparison of a breath hydro-gen method with direct measurement using a humanileostomy model. Am / Gastroenterol 81:115-22, 1986
26. Vaaler S, Hanssen KF, Aagenaes O: Plasma glucose andinsulin responses to orally administered carbohydrate-richfoodstuffs. Nutr Metab 24:168-75, 1980
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28. Tappy L, Wursch P, Randin JP, Felber JP, Jequier E: Met-abolic effect of pre-cooked instant preparations of beanand potato in normal and in diabetic subjects. Am J ClinNutr 43:30-36, 1986
29. Jenkins DJA, Wolever TMS, Taylor RH, Barker HM, Fiel-den H, Jenkins AL: Effect of guar crispbread with cerealproducts and leguminous seeds on blood glucose con-centrations of diabetics. Br Med I 281:1248-50, 1980
30. Coulston AM, Greenfield MS, Enger F, Tokey T, ReavenGM: Effect of source of dietary carbohydrate on plasmaglucose and insulin responses to test meals in normal sub-jects. Am j Clin Nutr 33:1279-82, 1980
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33. Nuttall FQ, Mooradian AD, DeMarais R, Parker S: Theglycemic effect of different meals approximately isoca-loric and similar in protein, carbohydrate, and fat contentas calculated using the ADA exchange lists. Diabetes Care6:432-35, 1983
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35. Collier GR, Wolever TMS, WongGS, Josse RG: Predictionof glycemic response to mixed meals in non-insulin-de-pendent diabetic subjects. Am j Clin Nutr 44:349-52,1986
36. Jenkins DJA, Wolever TMS, Jenkins AL, Lee R, Wong GS,Josse R: Glycemic response to wheat products: reducedresponse to pasta but no effect of fiber. Diabetes Care6:155-59, 1983
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48. Thorne MJ, Thompson LU, Jenkins DJA: Factors affectingstarch digestibility and the glycemic response with specialreference to legumes. Am J Clin Nutr 38:481-88, 1983
49. Yoon JH, Thompson LU, Jenkins DJA: The effect of phyticacid on in vitro rate of starch digestibility and blood glu-cose response. Am ) Clin Nutr 38:835-42, 1983
50. Thompson LU, Yoon JH, Jenkins DJA, Wolever TMS,Jenkins AL: Relationship between polyphenol intake andblood glucose response of normal and diabetic individ-uals. Am ) Clin Nutr 39:745-51, 1984
51. Rea RL, Thompson LU, Jenkins DJA: Lectins in foods andtheir relation to starch digestibility. Nutr Res 5:919-29,1985
52. Jenkins DJA, Wolever TMS, Leeds AR, Gassull MA, Di-lawari JB, Goff DV, Metz GL, Alberti KGMM: Dietaryfibers, fiber analogues and glucose tolerance: importanceof viscosity. Br Med) 1:1392-94, 1978
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