Geoff O’Sullivan – Applications ManagerSeptember 2003
FIT – Reading University
Glycaemic Index A Practical MeasureFor Maintaining A Healthy Diet?
Contributors: Helen Mitchell Geoff Livesey Stuart Craig Julian Stowell
Geoff O’Sullivan
AGENDA
• GI Concept and definitions
• Targeting disease risk reduction
• The evidence
• Communicating GI
Glycaemic Index A Practical Measure
Concept first developed in 1981 - University ofToronto - to help determine which foods werebest for people with diabetes
There is no indication that the glycaemicindices of polyols or speciality carbohydratesrank with their molecular size or number ofcarbon atoms per molecule
Molecular size is a poor indicator ofphysiological attributes
However, slow and incomplete digestion,absorption and metabolism play a key role inrelative GI measurement
Glycaemic Index
Glycaemic Response
The GI of foods is simply a ranking of foods based on their immediate effect on blood sugar levels To make a fair comparison, all foods are compared with a reference food such as pure glucose Today we know the GI factors of thousands of different food items that have been listed in International tables, following a standard method
Foods with a GI below 55 are classed as low GI
0 1 2 3 4 5
Time (h)
Pla
sma
glc.
con
c. (
mg%
)
GLC PDX
Glycaemic Index
Glycaemic index ( or GI factor) is a ranking offoods from 0 – 100that tells us whether a food will raise bloodsugar levels just a little, moderately ordramatically
Low GI <55Intermediate GI foods 55 - 70High GI foods > 70
Evolution of GI Methodology
The following can be determined:
• Glycaemic Index• Glycaemic Effect• Glycaemic Load• Insulin Index
For individual components, individual foods orwhole diets
Comparisons are usually made versus glucoseor white bread using
• 50 grams of carbohydrate• same serving size, or• same calorie value
Standardization of methodology is the subjectof intense debate
Definition
The incremental area under the blood glucoseresponse curve(AUC) of a 50g carbohydrateportion of a test food expressed as a percent ofThe response to the same amount ofcarbohydrate from a standard food(normally glucose) taken by the same subject.
Glycaemic Index
1 hour 2 hour 1 hour 2 hour
Blo
od s
ugar
leve
ls
Glucose ( reference) 50g Fructose 50g
100%23%
GI Factor 100 GI Factor 23
Glycaemic Index
Glycaemic & Insulin Index
Insulin demand exerted by foods is important forlong-term health, but it doesn't necessarily followthat we need an insulin index of foods instead ofa glycemic index
When both have been tested together, theglycaemic index is extremely good at predictingthe food's insulin index. In other words,a low-GI food has a low insulin index value anda high-GI food has a high insulinindex value
An insulin index of foods: the insulin demandIs generated by 1000-kJ portions of foods
Glycaemic & Insulin Index
There are some instances, however, where afood has a low glycaemic value but a high insulinindex value
This applies to dairy foods and to some highlypalatable energy-dense "indulgence foods“ Some foods (such as meat, fish, and eggs) thatcontain no carbohydrate, just protein and fat(and essentially have a GI value of zero), stillstimulate significant rises in blood insulin
There is however good correlation for mostfoods – are the beneficial effects just do toInsulin secretion?
PROTEIN-RICH FOODS GI IS
Eggs 42 31
Cheese 55 45
Beef 21 51
Lentils 62 58
Fish 28 59
Baked beans 114 120
Glycaemic & Insulin Index
American Journal of Clinical Nutrition 1997, Vol. 66: pages 1264-1276 by Susanne HA Holt, Janette C. Brand Miller, and Peter Petocz.
Glycaemic & Insulin Index
Glycaemic & Insulin Index
Glycaemic Index
0
2
4
6
8
10
12
14
0 20 40 60 80 100 120
Glycaemic index (Glucose=100)
Freq
uenc
y (%
all
obse
rvati
ons)
Glycaemic Index of Selected Foods
• Apple 38• Banana 55• Biscuits 55 to 80• Bread
- French 95- Pitta 57- White 79- Wholemeal 69
• Breakfast cereals- All-bran 42- Cornflakes 84- Porridge 42
• Rice- Basmati 58- Glutinous, white 98
• Coca cola 63• Soya beans (boiled) 18• Spaghetti (wholemeal) 37• Potatoes
- French fries 75- Baked 85
• Sucrose 65• Watermelon 72
Low Glycaemic Index Diets
• Control established diabetes• Help people lose weight• May help lower blood lipids• Improve body’s sensitivity to
insulin• May help reduce the risk of heart
disease in some people• Less likely to develop diabetes in
middle age• May improve sports performance
• To make the change use more:– Low GI breakfast cereals
based on wheatbran and oats
– Wholegrain breads especially barley and rye
– Pasta or less potatoes– Low GI fruits: pears, plums,
apples– Use Low GI ingredients in
formulating processed foods - Fructose, Litesse, Lactitol, Xylitol
Why ? - Health Implications
Health problems related to overweight arebecoming the major health concernWorldwide
Overweight and obesity greatly increase risk of among others:
- Diabetes 2
- Cardiovascular diseases
- High blood pressure
- High levels of cholesterol
- Certain types of cancer
The World Health Organization (WHO): Globally, Overweight is a bigger problem than undernourishment
Why ? - Health Implications
World Health Organisation and Food and Agriculture Organisation Recommendations(1)
• People in industrialised countries should base their diets on low-GI foods to prevent the most common diseases of affluence
• Terms such as complex carbohydrate are now recognised as having little nutritional or physiological significance
• Total carbohydrate and GI value of food is more relevant
(1) Food and Agriculture Organisation /World Health Organisation. Carbohydrates in human nutrition. Report of a joint FAO/WHO report. Rome 14-18 April 1997. Paper 66 1998. FAO Food and Nutrition
Why ? - Health Implications
To meet the body's daily energy and nutritional needs while minimizing risk for chronic disease, adults should get 45 percent to 65 percent of their calories fromcarbohydrates, 20 percent to 35 percent from fat, and 10 percent to 35 percent from protein, says the newest report on recommendations for healthy eating from the National Academies' Institute of Medicine. To maintain cardiovascular health at a maximal level, regardless of weight, adults and children also should spend a total of at least one hour each day in moderately intense physical activity, which is double the daily minimum goal set by the 1996 Surgeon General's report
Revised Guide-lines – In US
Overview
Recent large studies have provided evidencethat a diet high in glycaemic carbohydratesmay be detrimental to health
The Evidence – large Studies
Health Benefits of Low GlycaemicCarbohydrates
Glycemic Index vs Glycemic Load
Glycemic Index (GI) measures thepostprandial blood glucose response to afood that contains 50 g of carbohydrate
Glycemic Load (GL) uses the GI of eachfood, the carbohydrate content in eachserving (from USDA) and the averagenumber of food servings per day (from thedietary questionnaire) to calculate the totalglucose response and insulin demand
The Evidence
Prospective Epidemiological Studies
Salmeron et al from the Harvard School ofPublic Health published two cohort studies in1997 in women1 and men2 that examined therelationship between
Glycemic diets,
Low fiber intake, and
risk of non-insulin-dependent diabete
mellitus (NIDDM).
The Evidence
Prospective Epidemiological Studies
The study populations were from the Nurses’Health Study of 65,173 women1 and the HealthProfessionals Follow-up Study of 51,529 men2.
They concluded that diets with a high GLand/or a low cereal fiber content increase riskof NIDDM in both women and men.
The Evidence
Salmeron et al Study in Women
2,502,30
2,05
2,17
1,801,62
1,511,28
1,00
0
0,5
1
1,5
2
2,5
Relative Risk of NIDDM
High (>165) Medium(165-143)
Low (<143)
High (>5.8)
Medium (2.5-5.8)
Low (<2.5)
Glycemic Load
Cereal Fiber Intake (g/d)
The Evidence
Salmeron et al Study in Men
2,17
1,04 0,97
1,03 1,10 1,06
0,810,60
1,00
0
0,5
1
1,5
2
2,5
Relative Risk of NIDDM
High (>165) Medium(165-143)
Low (<143)
High (>5.8)
Medium (2.5-5.8)
Low (<2.5)
Glycemic Load
Cereal Fiber Intake (g/d)
The Evidence
Relative Risk of NIDDM by Glycemic Index Quintiles
1
1,1
1,2
1,3
1,4
1,5
60 65 70 75 80
Glycemic Index
Rel
ativ
e R
isk
of
NID
DM
Women
Men
The Evidence
Relative Risk of NIDDM by Glycemic Load Quintiles
1
1,1
1,2
1,3
1,4
1,5
100 120 140 160 180 200 220
Glycemic Load
Rel
ativ
e R
isk
of
NID
DM
Women
Men
The Evidence
Prospective Epidemiological Studies
Another study by Liu et al3 in 2000 looked at theeffects of dietary GL, carbohydrate intake, andrisk of coronary heart disease (CHD) in womenusing the Nurses’ Health Study (75,521women).
They concluded that a high dietary GL fromrefined carbohydrates increases the risk ofCHD, independent of known coronary disease
risk factors.
The Evidence
Liu et al Study in Women
1,11
2,03 1,97
0,94
1,20
1,74
1,00 1,05
1,42
0
0,5
1
1,5
2
2,5
Relative Risk of CHD
<23 23-29 >29
Tertile 1
Tertile 2
Tertile 3
BMI (kg/m2)
Glycemic Load
The Evidence
Relative Risk of CHD by Glycemic Load Quintiles
1
1,2
1,4
1,6
1,8
2
100 120 140 160 180 200 220
Glycemic Load
Rel
ativ
e R
isk
of
CH
D
Women
The Evidence
Post-meal glucose is an important determinantof HbA1c glycosylated haemoglobin
concentrations
Glycosylated haemoglobin (HbA1C)
correlates with cardiovascular disease risk
(macrovascular)
diabetes complications (microvascular)
Normal HbA1C is approximately 4.5%
Typical 'at risk' levels - 8 - 10%
Reduction of 1% correlates with 20%
disease risk reduction
-Khaw et al (2001) BMJ 322 1-6
Glycaemic & Insulin Index
History of heart attack and stroke - Khaw et al (2001) BMJ 322, 1-6 (Norfolk, UK)
02
468
10
121416
1820
4 5 6 7 8 9
Glycosylated haemoglobin (%)
Perc
enta
ge w
ith h
isto
ry
‘Healthy’ men 45-79 yrs (n>4500)
17% 48%
5%
30%
A 1% fall in glycosylated haemoglobin corresponds to a 20% fall in heart attack and stroke
The Evidence
0
1
2
3
4
4 5 6 7 8 9
Glycosylated haemoglobin (%)
Re
lati
ve
ris
k
All cause mortality in
men, 1995-99
Khaw et al (2001) BMJ 322, 1-6 (EPIC-Norfolk,
UK)
The Evidence
0
2
4
6
8
10
4 5 6 7 8 9
Glycosylated haemoglobin (%)
Re
lati
ve
ris
k Cardiovascular disease in men,
1995-99 Khaw et al (2001)
BMJ 322, 1-6 (Norfolk EPIC Study,
UK)
The Evidence
024681012
4 5 6 7 8 9
Glycosylated haemoglobin (%)
Re
lati
ve
ris
k Ischaemic heart disease in men,
1995-99 Khaw et al (2001)
BMJ 322, 1-6 (Norfolk, UK)
The Evidence
0
1
2
3
4
4 5 6 7 8 9
Glycosylated haemoglobin (%)
Rel
ativ
e ri
sk Non-cardiovascular
mortality in men,1995-99 Khaw et al (2001) BMJ 322, 1-6
(Norfolk, EPIC Study, UK)
The Evidence
-0.5
0
0.5
1
1.5
2
2.5
3
-1500 -500 500 1500 2500
Change in AUC post-prandial
glucose (mmol.L-1.240min)
Ch
ang
e in
Hb
A1
c (
%)
3 months a-glucosidase
inhibitor
Post-meal glucose, Type-2 DM
Brooks et al (1998) Diab Res Clin Prac 42, 175-
180
Lowering postprandial glucose concentrations lowers HbA1c in Type 2DM
Reduction Of - (HbA1C)
5.5
6
6.5
7
7.5
8
-10 10 30 50
Potato carbohydrates (g.day-1)
Hb
A1c
(%
)
EURODIAB IDDM Complication Study
Group Type-1 DM, HbA1c and Potatoes Buyken AE, Toeller M et al (2000) Diabetic Medicine 17, 351-359.
Leads to advice over intake of potatoes: Willetts Mediterranean diet pyramid has been altered to account fort this type of information
Reduction Of - (HbA1C)
Line of identity
0
2
4
6
8
10
12
14
5 7 9 11 13
HbA1c on high GI diet
Hb
A1
c o
n lo
w G
I die
t
Brand et al (1991) Diabetes Care 14, 95-101.
Diet GI Reduction 15% for 12 weeks in Type-2 DM
Reduction Of - (HbA1C)
Role of GI in Reducing HbA1C
A reduction in the GI of the diet by 15% for12 weeks led to about 2 percentage pointsreduction in HbA1C in Type 2 diabetics
Benefit is most observable in people withraised HbA1C
Many people have raised HbA1C withoutknowing it (and without having diabetes) andare at risk of CHD, stroke etc
Brand et al (1991) Diabetes Care 14, 95101
Mechanisms
Metabolic experiments suggest that a highdietary GL leads to adverse metabolicresponses, including hyperinsulinemia,hypertriglyceridemia, and low HDL-cholesterolconcentrations4.
These are strongly related to an individual’s underlying degree of insulinresistance5
The Evidence
Really an opportunity
What is often confused or forgotten in thediabetes debate is:
What is a healthy diet regime for a person withdiabetes is also healthy for the rest of us
This includes the use of low glycaemicprocessed foods
Using the glycaemic control concept, and anindication of glycaemic values on pack, thereis no further need to differentiate betweendiabetics and the healthy population
It may be hard to believe that healthy eatingand everyday foods can actually go together– but it’s true!
• Glycaemic Index Label and Symbol programme• Which foods can have GI and symbol on them
– In line with ANZFA’s recommendation for– Nutrition Function Claims– Only foods that meet their criteria for total and saturated fat,
sodium, and nutrient density will be able to have the glycaemic index symbol printed on their label.
– In addition food products must contain a least 10g of carbohydrate per serving and be a source of dietary fibre
– Foods meeting this criteria will be eligible - regardless of GI– Healthy high GI foods will not be “demonised” by the
programme– By placing GI directly on the label - consumers can follow the
national (ANZFA) and International ( WHO/FA0) dietary recommendations
Communicating GI
Communicating GI
Evening Standard, Friday 1 March 2002
• “How the Glycaemic Index can help you”BBC Good Food Magazine March 2002
• “Good and Bad Carbohydrates” Country Living November 1999• “X marks the spot for a new style of weight loss” Sunday Times 2002• “Beware! Carbs are the New Fat” Marie Claire March 2002• “Never mind calories – think GI” Independent 14 March 2002• “Get into good sugar management” Alternative Health 6 June 2000• “The fuel that really makes you perform” The Times 3 October 2000• “Eat well with diabetes” The Times 26 September 2000• “The good heart diet” The Times 19 September 2000• “The diet revolution” The Times 12 September 2000• “How to eat fat and stay slim” The Times 29 June 2000• “Why bread may help you slim” Daily Mail May 2001• Womans Hour – X Factor Diet. BBC Radio 4 , 22 January 2002
Communicating GI
Communicating GI
GI Pocket guides in this series:People with diabetes
Sports Nutrition
Top 100 Low GI Foods
Your Child
Sugar and energy
Losing Weight
Your heart
Juvenille Diabetes
Other Books include:
Eat yourself slim – Michel Montignac
Dine Out and Lose Weight – Michel Montignac
The 30-day Fat Burner Diet – Patrick Holford
Sugar Busters – Sam Andrew et al.
The X factor diet – Leslie Kenton
Communicating GI
References
1. Salmeron, J., Manson, J.E., Stampfer, M.J., Colditz, G.A., Wing, A.L. & Willett, W.C. (1997) JAMA 277, 472-7
2. Salmeron, J., Ascherio, A.O., Rimm, E.B., Colditz, G.A., Spiegelman, D., Jenkins, D.J., Stampfer, M.J., Wing, A.L. & Willett, W.C. (1997) Diabetes Care 20, 545-50
3. Liu, S., Willett, W.C., Stampfer, M.J., Hu, F.B., Franz, M., Sampson, L., Hennekens, C.H. & Manson, J.E. (2000) Am J Clin Nutr 71, 1455-61
4. Liu, S., Manson, J.E., Hu, F.B. & Willett, W.C. (2001) Am J Clin Nutr 73, 130-1
5. Jeppesen, J., Schaaf, P., Jones, C., Zhou, M.Y., Chen, Y.D. & Reaven, G.M. (1997) Am J Clin Nutr 65, 1027-33
The Evidence