You
will find lots of information on the official Low Gycemic Index
website here.
The
glycemic index, glycaemic index, or GI is a measure of the effects
of carbohydrates on blood sugar levels. Carbohydrates that break
down quickly during digestion and release glucose rapidly into
the bloodstream have a high GI; carbohydrates that break down
more slowly, releasing glucose more gradually into the bloodstream,
have a low GI. The concept was developed by Dr. David J. Jenkins
and colleagues in 1980–1981 at the University of Toronto
in their research to find out which foods were best for people
with diabetes. A lower glycemic index suggests slower rates
of digestion and absorption of the foods' carbohydrates and
may also indicate greater extraction from the liver and periphery
of the products of carbohydrate digestion. A lower glycemic
response usually equates to a lower insulin demand but not always,
and may improve long-term blood glucose control and blood lipids.
The insulin index is also useful for providing a direct measure
of the insulin response to a food.
The
glycemic index of a food is defined as the area under the two
hour blood glucose response curve (AUC) following the ingestion
of a fixed portion of carbohydrate (usually 50 g). The AUC of
the test food is divided by the AUC of the standard (either
glucose or white bread, giving two different definitions) and
multiplied by 100. The average GI value is calculated from data
collected in 10 human subjects. Both the standard and test food
must contain an equal amount of available carbohydrate. The
result gives a relative ranking for each tested food.
The
current validated methods use glucose as the reference food,
giving it a glycemic index value of 100 by definition. This
has the advantages of being universal and producing maximum
GI values of approximately 100. White bread can also be used
as a reference food, giving a different set of GI values (if
white bread = 100, then glucose ˜ 140). For people whose
staple carbohydrate source is white bread, this has the advantage
of conveying directly whether replacement of the dietary staple
with a different food would result in faster or slower blood
glucose response. The disadvantages with this system are that
the reference food is not well-defined and the GI scale is culture
dependent. (source Wikipedia )
