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Int. J. Pharm. Med. & Bio. Sc. 2012 S Thilakavathy and N Karthiga Pandeeswari, 2012
Int. J. Pharm. Med. & Bio. Sc. 2012
ISSN 2278 – 5221 www.ijpmbs.com
Vol. 1, No. 2, October 2012
© 2012 IJPMBS. All Rights Reserved
Review Article
THE GLYCEMIC INDEX - A SCIENCE BASED DIET
1* 1
S Thilakavathy and N Karthiga Pandeeswari
*Corresponding Author: S Thilakavathy,thilaka.ravichandran@gmail.com
Lifestyle diseases, like coronary disorders, high blood pressure, diabetes or obesity cause the
predominant part of all the mortality worldwide as countries become more industrialized.. More
importantly, they are potentially preventable and can be lowered by modifications in diet with low
glycemic index foods,and changes in lifestyle and environment. Foods containing carbohydrates
that are quickly digested have the highest glycemic index, since the blood sugar response is
fast and high. Slowly digested carbohydrates have a low glycemic index, since they release
glucose gradually into the bloodstream. A healthy low GI diet is easily able to achieve these
goals, perhaps better than other dietary interventions. Low GI diet can achieve greater reduction
in blood pressure, increase the body’s sensitivity to insulin, improve diabetes control, reduce
the risk of heart disease, and reduce blood cholesterol level, reduction in weight. Low GI foods,
, delay hunger and help the body burn more fat and less muscle by increasing satiety or fullness
after eating, low GI foods help reduce the calories consumed later in the day and reduce
postprandial blood glucose levels, the beneficial role for low GI diets by reducing oxidative damage,
thereby lowering heart disease risk.
Keywords: Low Glycemic Index, Reduce blood glucose, Cholesterol, Heart disease, Dietary
interventions
INTRODUCTION routinely adopt and the way we tend to
Health is the level of functional or metabolic (involuntarily) live our daily life, unless coerced to
change by some external stimulus. Lifestyle is
efficiency of a living being. In humans, it is the thus mainly dependent on psycho-social and
general condition of a person’s mind, body and environmental factors and, to a smaller extent,
spirit, usually meaning to be free from illness, on genetic influences. Lifestyle is developed in
injury or pain (as in ‘good health’ or ‘healthy’) the form of a set pattern of behaviour, very
(World Health Organization, 2006). According to gradually, over many years, in the way we eat,
the World Health Organization, the main drink, exercise, use intoxicants, and are
determinants of health include the social and predisposed to own health care and personal
economic environment, the physical environment, protection, sexual practices and so on. Since
and the person’s individual characteristics and these behavioral patterns are acquired very
behaviors (World Health Organization, 2011). gradually, changing them becomes a difficult
‘Lifestyle’, in the context of preventive health proposition and needs a lot of persuasiveness
care, indicates the behavioural patterns which we as well as persistent approach on the part of the
1 Department of Food Science and Nutrition, Avinashilingam Institute for Home Science and Higher Education for Women, Coimbatore.
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Int. J. Pharm. Med. & Bio. Sc. 2012 S Thilakavathy and N Karthiga Pandeeswari, 2012
health care providers including health educators. associated with obesity in adult, but epi-
(Leeder et al., 2004). demiological studies in humans so far have been
Lifestyle diseases are that they appear to inconsistent.
become ever more widespread as countries The glycemic index ranks carbohydrate-
become more industrialized. containing foods on how quickly they elevate blood
They are the result of an inappropriate sugar levels. It is measured by comparing the
relationship of people with their environment. The increase in blood sugar after eating 50 grams of
lifestyle diseases, like coronary disorders, heart carbohydrate from a single food with the increase
diseases, high blood pressure, diabetes or in blood sugar after eating the same quantity of
carbohydrate from a reference food, which is
obesity cause the predominant part of all the either pure glucose or white bread. The average
mortality worldwide. These are such diseases change in blood sugar levels over the next two
which occur resulting from the way people live hours, compared to the change in blood sugar
their lives. In developed countries and societies, levels after consuming the reference food, is the
these diseases become more frequent as glycemic index value of that particular food. The
economic growth starts. More importantly, they blood sugar response of the reference food is
are potentially preventable and can be lowered given a value of 100 and all other foods are
by changes in diet, lifestyle and environment compared to this value (Brand-Miller et al., 2003).
(Bhikha, 2007). Foods containing carbohydrates that are
Type 2 Diabetes Mellitus (T2DM) is a disease quickly digested have the highest glycemic index,
resulting mainly from the dysfunction in the since the blood sugar response is fast and high.
carbohydrate metabolism, characterized by Slowly digested carbohydrates have a low
hyperglycemia. Its prevalence in recent decades glycemic index, since they release glucose
has been increasing, reaching nearly 6% of the gradually into the bloodstream (Brand-Miller et al.,
population, (Sociedade Brasileira, 2006) data 2003). In general, most refined carbohydrate-rich
shows that in the world there are about 246 million foods have a high glycemic index, while non
people with diabetes (IDA, 2006) and this number starchy vegetables, fruits and legumes tend to
is expected to grow to 366 million in 2030 (Wild have a low glycemic index (Ludwig, 2002).
et al., 2004) . Glycemic index values are grouped into three
categories:
WHAT IS GLYCEMIC INDEX? High GI 70 or higher
Glycemic index (GI) is a measure of the glucose Intermediate GI 56-69
response to ingestion of a fixed amount of
available carbohydrates; glycemic load (GL) Low GI 0-55
combines the qualitative and quantitative Determining Glycemic index of food
measures of carbohydrates and is the product of Foods with carbohydrates that break down
the GI and the amount of carbohydrates quickly during digestion and release glucose
consumed. High-GI diet has been positively rapidly into the bloodstream tend to have a high
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Int. J. Pharm. Med. & Bio. Sc. 2012 S Thilakavathy and N Karthiga Pandeeswari, 2012
GI; foods with carbohydrates that break down whose staple carbohydrate source is white
more slowly, releasing glucose more gradually bread, this has the advantage of conveying
into the bloodstream, tend to have a low GI. The directly whether replacement of the dietary staple
concept was developed by Dr. David J. with a different food would result in faster or
Jenkins and colleagues in 1980-1981 at slower blood glucose response. The dis-
the University of Toronto in their research to find advantages with this system are that the
out which foods were best for people reference food is not well-defined and the GI scale
with diabetes. A lower glycemic index suggests is race-dependent.
slower rates of digestion and absorption of the The GI of a food is influenced by many different
carbohydrate foods’ and may also indicate greater factors including the type of sugar (e.g., fructose
extraction from the liver and periphery of the vs glucose), the type of starch (e.g., amylose vs
products of carbohydrate digestion. A lower amylopectin), the gelatinization of the starch, the
glycemic response usually equates to a lower type of fiber (e.g., soluble vs insoluble), the
insulin demand but not always, and may improve processing of a food, and the presence of fat or
long-term blood glucose control (David and protein in a mixed meal. It cannot be easily
Jenkins, 2008) and blood lipids. The insulin predicted nor measured in vitro, which is a
index is also useful for providing a direct measure measure of carbohydrate digestibility rather than
of the insulin response to a food. the true in vivo response of a food on blood glucose
The glycemic index of a food is defined as the levels. There is now a significant body of evidence
incremental area under the two-hour blood demonstrating the benefits of healthy low GI diets.
glucose response curve (AUC) following a 12- Although a high carbohydrate diet has been shown
hour fast and ingestion of a food with a certain to worsen many of the features of insulin
quantity of available carbohydrate (usually 50 g). resistance, including postprandial glycemia and
The AUC of the test food is divided by the AUC of insulinemia, fasting hypertriglyceridemia, low
the standard (either glucose or white bread, giving high-density lipoprotein (HDL) levels and
two different definitions) and multiplied by 100. fibrinolysis, this is not seen when the carbohydrate
Both the standard and test food must contain an comes from low GI sources. Many studies show
equal amount of available carbohydrate. The that low and high GI foods have significantly
result gives a relative ranking for each tested food different effects on metabolism (Jenkins et al.,
(Brouns et al., 2005). 2002).
The current validated methods use glucose High GI meals result in a rapid increase in blood
as the reference food, giving it a glycemic index glucose and insulin levels followed by reactive
value of 100 by definition. This has the hypoglycemia, counterregulatory hormone
advantages of being universal and producing secretion, and elevated free fatty acid
maximum GI values of approximately 100. White concentrations, which may then lead to â-cell
bread can also be used as a reference food, dysfunction, dyslipidemia, and endothelial
giving a different set of GI values (if white bread = dysfunction (Ludwig, 2002). Although the GI
100, then glucose H” 140). For people predicts the potential of a food’s carbohydrate to
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Int. J. Pharm. Med. & Bio. Sc. 2012 S Thilakavathy and N Karthiga Pandeeswari, 2012
raise blood glucose levels, the overall blood slows down the access of digestive enzymes to
glucose response to a food or meal is determined the starch inside. Finely milled flours generally
by both the quantity and quality (GI) of the have a high GI. Coarse, stone-ground flours have
carbohydrate consumed (Brand-Miller et al., larger-sized particles and lower GIs (Brand-Miller
2003) . et al., 2003).
Thus the concept of glycemic load—defined Type of Starch: The two types of starch in foods,
as the GI multiplied by the amount of carbohydrate amylose and amylopectin, have different effects
per serving of food in grams—was introduced as on GI. Amylose molecules are harder to digest
a measure of the overall effect of a food on blood than amylopectin molecules. Legumes and
glucose and insulin levels. Dietary GL can be basmati rice have a higher ratio of amylose to
reduced in two ways: either by lowering the GI of amylopectin, and therefore, have a lower GI than
the carbohydrate or by reducing the total foods with more amylopectin. For example, the
carbohydrate in the diet, but the metabolic effects GI of basmati rice is 58; instant rice is 87 (Brand-
of these changes are likely to be different. Defects Miller et al., 2003) .
in carbohydrate metabolism, which characterize Fiber: The extent that fiber affects GI is unclear.
diabetes, mean that the GI and GL of a food or Some researchers believe that viscous, soluble
meal are particularly relevant to the management fiber thickens the mixture of food in the digestive
of this condition (Wolever and Mehling, 2002). tract, which slows response, and a lower GI.
What Determines a Food’s Glycemic Legumes and oats contain soluble fiber and have
Index? low GIs (Willett, 2001).
Several factors affect the glycemic index of a Sugar: GI is affected by the type of sugar in a
food: food. Sucrose (table sugar), which is made up of
Cooking Method: Heat, amount of water and glucose and fructose, has a lower GI than glucose
cooking time affect a food’s GI. During cooking, because half of the sucrose molecule is made
water and heat expand the starch granules to up of fructose, a type of sugar that elicits a very
varying degrees. Foods containing starch that has small blood sugar response. For example, the GI
swollen (or gelatinized) to the bursting point, like of sucrose is 68; the GI of glucose is 100. It would
boiled or baked potatoes, are more easily seem that adding sugar to a meal should lower
digested, and therefore, have higher GIs, than the GI, but, surprisingly, a few studies have not
foods containing starch granules that are less found this to be so (Willett, 2001).
gelatinized, like oatmeal, brown rice, and al dente Fat: Fat increases the time it takes for food to
spaghetti. For example, the GI of a baked potato leave the stomach and enter the intestine. By
is 85; brown rice is 50 (Brand-Miller et al., 2003) . slowing the rate that carbohydrates are digested
Processing Method: Grinding, rolling or milling in the intestine, fat-containing foods may temper
starchy foods reduces particle size and makes it the rise in blood sugar and yield a lower GI than
easier for water to be absorbed and digestive similar foods without fat. For example, the GI of
enzymes to attack the food. Processing can also potato chips is 57, French fries are 75 and baked
remove the fibrous outer coat of the grain that potato is 85. However, that does not make potato
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