The take home message from health authorities for the past three decades has been 'eat less fat, especially saturated fat'. Now a new paradigm is arising: that the processed carbohydrates which replaced the energy from fat, may increase the risk of obesity, diabetes and heart disease more so than fat - a finding that has enormous implications for the Australian food and agricultural industry. Both quantity and quality of carbohydrate are relevant to the debate. The rate of digestion and absorption of carbohydrates is assessed as their ‘glycemic index' (GI). This lecture will focus on well-designed studies demonstrating that carbohydrates that are slowly digested and absorbed (i.e. low GI carbs) are good for health and reduce risk factors associated with lifestyle-related diseases such as diabetes. Improving carbohydrate quality is therefore a better approach to health and sustainability issues than ‘ditching the carbs'. Professor Jennie Brand-Miller is recognised for her work on carbohydrates and diabetes. Her books under the series title The New Glucose Revolution have sold over 3.5 million copies worldwide and appeared in 12 languages.

1. Are „refined‟ carbohydrates worse
than saturated fat?
Jennie Brand-Miller
School of Molecular Bioscience
& Boden Institute of Obesity, Nutrition and Exercise
The University of Sydney

2. The Australian Context 2010
 One in 2 adult males is
overweight or obese
 One in 3 adult females
 One in 4 has the metabolic
syndrome
 One in 4 has high blood
sugars
 One in 5 children is
overweight or obese
 Kids Eat, Kids Play Survey 2008
Dunstan et al. Diabetes Care 2002

3. The current diet-heart paradigm
 High intake of saturated fat and cholesterol
increases the risk of cardiovascular disease
 Eat a diet that is low in fat, particularly saturated
fat and high in complex carbohydrate
 “Eat plenty of cereals, including breads, rice, pasta &
noodles, preferably wholegrain”
 Has this strategy been successful?

4. Carbohydrate and obesity
Increasing obesity and higher CHO intake have gone hand in hand
Liu et al. Am J Clin Nutr 2004

5. Do refined sugars play a role?
But are we eating more?

6. In Australia, refined sugar intake has
declined 25% in 25 y
Source: FAO-WHO Stats, 2010

7. Refined grains and weight gain
Change in weight over 12 years in 74,000 women
p < 0.0001
Adjusted for age, exercise, smoking, alcohol, caffeine, HRT, total
energy, fat type, protein and BMI at baseline
Liu et al. AJCN 2003

8. Obesity and type 2 diabetes go hand in hand

9. Diabetes prevalence has doubled
Australian adults over 25 y, n = 11,245,
%
Dunstan et al. Diabetes Care, 2002

10. Almost 1 in 4 Australians
over 25 y has either
diabetes or pre-diabetes
ie impairments in carbohydrate metabolism that lead
to dangerously high blood glucose concentrations
Dunstan et al. Diabetes Care, 2002

11. Why high glucose is harmful
Insulin demand
Glycaemia Insulinemia
resistance
Oxidative stress
Inflammation
Endothelial dysfunction
Coagulation and fibrinolysis
-cell and mitochondrial dysfunction
Advanced glycated endproducts (AGEs)

12. Why high glucose is harmful
Insulin demand
Glycaemia Insulinemia
resistance
Oxidative stress
Inflammation
Complications
Endothelial dysfunction
Cardiovascular disease
Coagulation and fibrinolysis
Blindness
-cell and mitochondrial dysfunction
Kidney failure
Advanced glycated endproducts (AGEs)
Nerve damage & amputations

13. The gold standard of
scientific evidence
=
the meta-analysis

14. Replacing saturated fat with CHO
Increased risk of CVD in a pooled analysis of 11 cohort studies
CHO for SAFA (per 5% E increments)
On average,
7% higher risk
of CVD
CVD = cardiovascular disease Jakobsen et al. Am J Clin Nutr, 2009

15. Replacing saturated fat with PUFA
Decreased risk of CVD in a pooled analysis of 11 cohort studies
PUFA for SAFA (per 5% E increments
CVD = cardiovascular disease Jakobsen et al. Am J Clin Nutr, 2009

16. The biggest intervention trial
n ~ 50,000 subjects
Howard et al. JAMA 2006

17. No difference between groups
Kaplan-Meier estimates of cumulative hazards for CVD (MI,
CHD death or revascularization) and stroke
Howard et al. JAMA 2006

18. Classifications of carbohydrate
 Simple vs complex
 eg sugars vs starches
 Dietary fibre content
 Extent of processing
 whole grains vs refined grains
 Glycemic index
 Postprandial glycaemia

19. Carbohydrates are the only food
constituents that directly raise
blood glucose
Photo: Suat Eman

20. Gram-for-gram, carbs vary in
their glycemic „potency‟
Pounding waves Gentle trickle
“Gushers” “Tricklers”

21. The glycemic index
Photo: Renjith Krishnan
 A tool to rate the glycemic potential of the
carbohydrates in different foods (as eaten)

22. Glycemic index methodology
 Compares foods gram-for-gram of carbohydrate
 Compares their „area under curve‟ over 2 hours
 Relative to a reference food
 Usually 50 g glucose load
 GI = 100
 Published GI = 10 subjects
 640 datapoints in total

23. Examples of high and low GI carbs
Searchable database at www.glycemicindex.com
High GI (>70) Low GI (<55)
 Potatoes  Pasta and noodles
 White bread  Legumes
 Wholemeal bread  Dairy foods
 Most rices (eg Jasmine)  Most fruit & vegetables
 Most breakfast cereals  Somes rices (eg Basmati)
 Some breads
 Most low-fat snacks
 Some breakfast cereals
Sugary foods fall in the low to moderate GI range

24. Glycemic potency is a property
of the food, not the person
 Stomach emptying
 Speed of digestion
 Speed of absorption

25. Starch gelatinisation increases GI
1 2
raw
starch
granule
3 4
“ghosts”
Fully gelatinised starch

26. Glycemic load (GL)
 GI = ranking of glycemic potential per unit of CHO
 GL = glycemic potential per serving of food
 GL = GI (%) x grams of CHO per serving
 Sample calculation
 GI of apple = 40
 GL of one apple = 6 g (40% x 15 g)
 GL of one slice of bread = 11 g (70% x 15 g)
 GL of whole diet has a 3-fold range (60 to 180 g)

27. How well does GL reflect
metabolic responses?

28. GL is better predictor of glucose
AUC than amount of CHO
1000 kJ portions of 120 single foods
Glycemic load Available carbohydrate (g)
Brand-Miller et al, under review

29. Protein and fibre are poor
predictors of glucose AUC
1000 kJ portions of 120 single foods
Protein (g) Fiber (g)
Brand-Miller et al, unpublished data

30. GL is a good predictor of insulinemia
1000 kJ portions of 120 single foods
Brand-Miller et al, unpublished data

31. Diet glycemic load and risk of CVD
Nurses‟ Health Study 20 y follow-up, 82,000 women
P = 0.003 for trend in fully adjusted model
p < 0.003 for trend after multivariate
adjustment
RR
Lowest Glycaemic load Highest
Halton et al. New Engl J Med, 2006

32. High GL diets increase CVD risk
EPICOR Study, n = 32,578 women, 8 y of followup
p < 0.005 in fully adjusted model
Cumulative
incidence of
CVD
Glycaemic load
Sieri et al. Arch Intern Med 2010

33. GL and risk of gestational diabetes
Gestational diabetes (GDM) over 8 y of follow up in 13,110 women
p < 0.03 after multivariate adjustment
P = 0.03
Zhang et al. Diabetes Care 2006

34. Low GI diets improve the
management of type 2 diabetes
RCT in type 2 diabetes over 24 wks (n = 210)
P < 0.001
HbA1c
High fibre diet
Low GI diet
Jenkins et al. JAMA 2008

35. Low GI diets reduce need for insulin in GDM
RCT of low GI vs high fibre diet, n = 63
P = 0.023
Moses et al. Diabetes Care, 2009

36. Low GI diet improves insulin sensitivity
In 12 type 2 subjects, 12 wk-crossover, weight maintenance
p < 0.001
M
Value
mg/k/min
Rizkalla et al. Diabetes Care 2004

37. Low GI diet improves insulin sensitivity
n = 49 women with polycystic ovary syndrome, 12 mths
P = 0.03
Change in
insulin
sensitivity
ISIGTT
Low GI High fibre
Marsh, Brand-Miller et al. Am J Clin Nutr, 2010

38. High GI diets increase diabetes risk
Meta-analysis mean RR = 1.4
Meta-analysis of low GI studies - Type 2 diabetes
M ode l Study na m e Sta tis tic s for e a c h s tudy Ra te ra tio a nd 9 5 % CI
Ra te Lowe r Uppe r
ra tio lim it lim it Z-Va lue
p-Va lue
Ho d g e e t a l . (8 ) 2 0 1 .3 6
04 0 .9 5 1 .9 5 1 .6 8 0 .0 9 4
Sa l m e ro n e t a l . (6 )11 9 7 7
.3 9 1 .0 9 1 .7 2 2 .7 4 0 .0 0 6
Sa l m e ro n e t a l . (7 )11 9 7 7
.3 9 1 .0 2 1 .8 4 2 .1 1 0 .0 3 5
Zh a n g e t a l . (1 0 ) 2 1 .36
00 0 1 .0 0 1 .6 8 1 .9 8 0 .0 4 7
Sc h u l z e e t a l . (9 ) 2 0 0 9
1 .5 4 1 .2 1 2 .0 9 3 .3 0 0 .0 0 1
Fi x e d 1 .3 9 1 .2 3 1 .5 7 5 .3 3 0 .0 0 0
Ra n d o m 1 .3 9 1 .2 3 1 .5 7 5 .3 3 0 .0 0 0
0 .1 0 .2 0 .5 1 2 5 10
Favours hi gh G I Favours l ow G I
Aj u
d sted GI - val i dated stu i es o y
d nl
Favours high GI Favours low GI
Barclay et al. Am J Clin Nutr 2008

39. GI/GL and weight control
Rate of weight loss and prevention of weight re-gain

40. Low GL diets and weight control
Changes in weight over 18 months in overweight subjects (n = 73)
All subjects Subjects with high
30 min insulin
Low fat diet
P = 0.02 Low GL diet
Ebbeling et al. JAMA 2007

41. The DIOGENES Study
Prevention of weight re-gain, 5 diets, n ~ 800, 26 weeks
High CHO +
low GI
High protein
+ low GI
Larsen et al. NEJM, in press

42. Postprandial glycemia is relevant
Prevention and And also to ...
management of…
 Type 1 diabetes
 Type 2 diabetes
 PCOS
 Gestational
diabetes  Pregnancy outcomes
 CV disease  Sport
 Obesity  Cognition

43. The challenge for the food industry
 The GI of modern diet rests in their hands
 Cooking and processing increase the degree of
starch gelatinisation (and hence GI)
 Convenience is ….food that cooks in 2 mins
 Humans are lazy…..they like soft, easy-to-chew food
 High GI foods may be addictive (Thornley et al, 2009)
 High GI foods are the norm

44. How to lower GI?
 Slow down carbohydrate digestion and/or absorption
 Reduce starch gelatinisation
 Increase the amylose: amylopectin ratio (genes)
 Reduce water, heating time, pressure,
 Use pasta technology
 Increase protein content
 Increase viscous fibre content (-glucans, psyllium, PGX ) ®
 Increase isoflavinols (some are amylase and a-glucosidase inhibitors)

45. Almera potatoes

46. Doongara rice

47. Burgen breads
Low GI

48. LoGIcane®

49. BarleyMax ®
Low GI

50. BarleyMax ®
Low GI

51. Informing food choices
 The Glycemic Index Foundation
 A not-for-profit organisation
www.gisymbol.com
 Founded in 2001 by consumer demand
 Endorses healthy, low GI foods
 Must meet strict nutrient criteria (category specific)

52. Are refined carbohydrates worse
than saturated fats?

54. “Diets high in either saturated fat or refined carbohydrates are
not suitable for heart disease prevention……refined
carbohydrates are likely to cause even greater metabolic
damage than saturated fat in a predominantly sedentary and
overweight population.

55. Take home messages
 Low fat diets have not been a success
 High glucose levels are undesirable
 Modern starchy foods tend to have a high GI
 Efforts should be made to reduce their GI
 Food innovations that lower GI are feasible
 Health should be a critical driver of
agricultural change