Glycemic index, glycemic load, and chronic disease risk
American Journal of Clinical Nutrition
March 2008, Vol. 87, No. 3, 627-637
Alan W Barclay, Peter Petocz, Joanna McMillan-Price, Victoria M Flood, Tania Prvan,
Paul Mitchell and Jennie C Brand-Miller
Nutrition, Human Nutrition Unit, University of Sydney, Sydney, Australia (VMF)
FROM ABSTRACT
Background:Inconsistent findings from observational studies have prolonged the controversy
over the effects of dietary glycemic index (GI) and glycemic load (GL) on the risk of
certain chronic diseases.
Objective:The objective was to evaluate the association between GI, GL, and chronic disease
risk with the use of meta-analysis techniques.
Design:A systematic review of published reports identified a total of 37 prospective cohort
studies of GI and GL and chronic disease risk.
Results:From 4 to 20 years of follow-up studies, a total of 40,129 incident cases were
identified. For the comparison between the highest and lowest quantiles of GI and
GL, significant positive associations were found in fully adjusted models of validated
studies for:Glycemic Index (GI) Glycemic Load (GL)
Type 2 diabetes 40% 27%
Coronary heart disease 25% NA
Breast cancer 8% NA
Gallbladder disease 26% 42%
All diseases combined 14% 9%
Conclusions:Low-GI and/or low-GL diets are independently associated with a reduced risk of
certain chronic diseases.The findings support the hypothesis that higher postprandial glycemia is a universal
mechanism for disease progression.
THESE AUTHORS ALSO NOTE:
“Worldwide, chronic diseases such as diabetes, cardiovascular disease, stroke,
and cancer contribute to 60% of all deaths, and the proportion is predicted to
increase to 75% by the year 2020.”“Increases in refined sugar intake have been accompanied by more subtle
changes in starchy foods, eg, processed cereal products have replaced more
traditionally processed grains.”“Because carbohydrate is the main dietary component affecting insulin
secretion and postprandial glycemia, it is implicated in the etiology of many chronic
diseases.”In 1981, the concept of the glycemic index (GI) was introduced to quantify
the glycemic response to carbohydrates in different foods.
“Glycemic load (GL), the mathematical product of the GI of a food and its
carbohydrate content, has been proposed as a global indicator of the glucose
response and insulin demand induced by a serving of food.”
RESULTS
The association between GI and GL and the increased risk of developing specific
diseases
Glycemic Index (GI) Glycemic Load (GL)
Type 2 diabetes 40% 27%
Heart disease 25% 57%
Stroke 2% 28%
All cardiovascular diseases
NA 41%
Breast cancer 9% NA
Colorectal cancer 11% 11%
Endometrial cancer 13% 72%
All cancers 8% NA
Gallbladder disease 26% 42%
Eye disease 10% NA
All diseases combined 14% 9%
“When all of the studies were analyzed, there were significant positive
associations between GI or GL and relative risks for type 2 diabetes, heart disease,
colorectal cancer, endometrial cancer, gallbladder disease, and all diseases
combined.”“In an analysis stratified by the 2 major chronic disease groups, cancer and
cardiovascular disease, there were significant positive associations between GI and
risk of all cancers and between GL and risk of all cardiovascular diseases.”
DISCUSSION
In a meta-analysis of 37 prospective observational studies, we found that
diets with a high GI or GL independently increased the risk of these diseases:
Type 2 diabetes GI 40% GL 27%
Heart disease GI 25% GL 57%
Gallbladder disease GI 26% GL 41%
Breast cancer GI 8% GL NA
All diseases combined GI 14% GL 9%
“There were more positive associations of greater magnitude between GI and
chronic disease than between GL and chronic disease.”
“Our findings support the hypothesis that postprandial hyperglycemia, in
individuals without diabetes, contributes to chronic disease.”
“Higher glucose concentrations are thought to play a direct pathogenic role in
the disease process.”Other studies have linked increased glucose levels to a variety of diseases,
including:1) All-cause mortality
2) Cardiovascular disease
3) Cancer risk
4) Colorectal cancer
5) Pancreatic cancer
There are plausible mechanisms linking the development of certain chronic
diseases with high-GI diets, specifically:
1) The same amount of carbohydrates from high-GI foods produces higher blood
glucose concentrations and a greater demand for insulin. The chronically increased
insulin demand may eventually result in pancreatic beta cell failure, and, as a
consequence, impaired glucose tolerance.
2) High glucose and insulin concentrations are associated with increased risk
profiles for cardiovascular disease.
3) The mitogenic action of insulin-like growth factors suggests a role in the
etiology of various cancers. Insulin stimulates a rise in insulin-like growth factors.
“Diets with a high GI, high GL, or both, independently of known confounders,
including fiber intake, increase the risk of chronic lifestyle-related diseases.”
“Irrespective of the level of carbohydrate intake, the GI of contributing
carbohydrate foods is important.”
“The findings indicate that the judicious choice of low-GI foods offers a similar
or higher level of protection as whole-grain foods or high fiber intake in the
prevention of chronic lifestyle-related disease.”
KEY POINTS FROM DAN MURPHY
GI = glycemic index
GL = glycemic load
1) “Low-GI and/or low-GL diets are independently associated with a reduced risk
of certain chronic diseases.”
2) “Higher postprandial glycemia is a universal mechanism for disease
progression.”
3) “Worldwide, chronic diseases such as diabetes, cardiovascular disease, stroke,
and cancer contribute to 60% of all deaths, and the proportion is predicted to
increase to 75% by the year 2020.”
4) “Increases in refined sugar intake have been accompanied by more subtle
changes in starchy foods, eg, processed cereal products have replaced more
traditionally processed grains.”
5) “Because carbohydrate is the main dietary component affecting insulin
secretion and postprandial glycemia, it is implicated in the etiology of many chronic
diseases.”
6) In 1981, the concept of the glycemic index (GI) was introduced to quantify
the glycemic response to carbohydrates in different foods.
7) “Glycemic load (GL), the mathematical product of the GI of a food and its
carbohydrate content, has been proposed as a global indicator of the glucose
response and insulin demand induced by a serving of food.”
8) “When all of the studies were analyzed, there were significant positive
associations between GI or GL and relative risks for type 2 diabetes, heart disease,
colorectal cancer, endometrial cancer, gallbladder disease, and all diseases
combined.”
9) “In an analysis stratified by the 2 major chronic disease groups, cancer and
cardiovascular disease, there were significant positive associations between GI and
risk of all cancers and between GL and risk of all cardiovascular diseases.”
10) “Our findings support the hypothesis that postprandial hyperglycemia, in
individuals without diabetes, contributes to chronic disease.”
11) “Higher glucose concentrations are thought to play a direct pathogenic role in
the disease process.”
12) Studies have linked increased glucose levels to a variety of diseases:
A)) All-cause mortality
B)) Cardiovascular disease
C)) Cancer risk
D)) Colorectal cancer
D)) Pancreatic cancer
13) “Diets with a high GI, high GL, or both, independently of known confounders,
including fiber intake, increase the risk of chronic lifestyle-related diseases.”
14) “Irrespective of the level of carbohydrate intake, the GI of contributing
carbohydrate foods is important.”
15) “The findings indicate that the judicious choice of low-GI foods offers a similar
or higher level of protection as whole-grain foods or high fiber intake in the
prevention of chronic lifestyle-related disease.”