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