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SA JOURNAL OF DIABETES & VASCULAR DISEASE
DIETICIAN REVIEW
VOLUME 8 NUMBER 2 • JUNE 2011
83
The role of the glycaemic index in diabetes
RUWAIDA JOGIAT
Abstract
T
here is much controversy about the use of the glycaemic
index (GI) for people with diabetes. What is well
established however is that good glycaemic control is
essential in this patient population. The GI is considered to
be one of the tools used to achieve optimal glycaemic control
in patients with diabetes.
Introduction
Diabetes can be associated with serious micro- and macrovascular
complications, including diabetic retinopathy, nephropathy and
neuropathy. These complications may be a result of poor glycaemic
control. A clear link has been established between glycaemic
control and the effect of macrovascular complications such as
coronary heart disease and stroke. These are the leading cause of
death in persons with diabetes.
1
Managing the diet of both type 1 and type 2 diabetics is one of
the cornerstones of the treatment of diabetes. The concept of the
GI was introduced by Jenkins
et al
. in 1981 and was developed to
help diabetics make good food choices, thereby achieving better
glycaemic control.
2
Improved glycaemic control reduces the risk of
the development of acute and chronic diabetic complications and
improves the quality of life of the patient.
3,4
The macronutrient that has the greatest impact on blood glucose
is carbohydrate.
1
The GI is based on the concept of the physiological
effect of foods that contain carbohydrates.
5
The physiological
effect of a carbohydrate refers to the ‘rate and magnitude in which
dietary glucose enters the blood stream’.
6
The GI score is low when the carbohydrate-containing food is
digested slowly and then absorbed in the small intestine. Foods
that break down quickly and result in higher levels of blood glucose
have a high GI.
2
What is the glyceamic index?
The GI of a particular food is defined as the glucose response
during the two-hour period after a test food is consumed.
1
This
is then compared to the GI of glucose which is the test standard.
6
White bread can also be utilised as a reference food but using white
bread as the test standard gives different GI values (if white bread is
100 then glucose is 140). The test and the standards contain a fixed
portion of available carbohydrate, usually 50 g.
7,8
The effect of the low-GI diet on glycaemic control
High-glycaemic index foods are digested and absorbed rapidly into
the blood stream, thereby increasing blood glucose levels. Chiu
et
al
. found that within two hours of eating a high-GI meal, blood
glucose levels doubled, compared to when a low-GI meal was
ingested.
3,4
The sharp rise in blood glucose stimulates the secretion
of insulin and inhibits glucagon release. This results in a high insulin-
to-glucagon ratio. Two to four hours post ingestion of the high-GI
meal, insulin levels remain high and glucagon levels remain low.
This results in low blood glucose levels or hypoglycaemia.
The consumption of a low-GI meal does not produce the same
series of hormonal reactions and subsequent hypoglycaemia. The
absorption of low-GI nutrients is slower and blood glucose levels
peak and fall more slowly.
2,9
The benefits of using a low-GI diet
There is a large volume of evidence demonstrating that the use of
a low-GI diet has an impact on metabolic disorders.
10
Yungsheng
et
al
. found that a lower GI diet was associated with a decreased risk
for the development of type 2 diabetes in women.
1
Forty individuals with poorly controlled diabetes were randomised
to a low-GI or an American Diabetes Association (ADA) diet. The
intervention consisted of eight educational sessions focusing on
either the low-GI or ADA diet. The low-GI diet group achieved
equivalent control of HBA
1c
levels using less diabetic medication.
Furthermore, the low-GI group was able to achieve dietary changes
from the materials and tools provided in the study, despite the
inability of the participants to attend as many group sessions as
those attended by the ADA diet group. The low-GI group also
achieved better glycaemic control.
1
Limitations of the low-GI diet
In some studies conducted, patients had difficulty understanding
the concept of the GI and its application. A further limitation of a
low-GI diet is that the fat content, type of fat and portion size need
Correspondence to: Ruwaida Jogiat
Dietitian, Pietermaritzburg
Tel: +27 (0)33 330-6077
Fax: +27 (0)33 394-1785
e-mail: ruwaida.jogiat@gmail.com
S Afr J Diabetes Vasc Dis
2011;
8
: 83–84.
Ruwaida Jogiat
