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HOW IS THE GI FACTOR OF FOODS DETERMINED?
Pure glucose is known to produce the greatest increase in blood-sugar levels
when compared to all other foods when fed in equal amounts of carbohydrate.
The GI Factor of pure glucose is therefore set at 100 and every other food is
ranked on a scale from 0 - 100 based on the effect it has on blood-glucose levels.
Note that the GI factor of a food cannot be predicted from its composition based
on the known GI Factor of other foods, to test the GI factor of a food you need
to test real food on real people.
Dr. Jenkins' team gave an amount of food containing 50g of carbohydrate to
a volunteer to eat. Over the following two hours a sample of blood is taken
from the volunteer every 15 minutes during the first hour and thereafter every
30 minutes. The blood-sugar level of each blood sample is measured and recorded
before being plotted on a graph. The area under the curve on the graph is then
calculated using a computer program. The volunteer's blood-sugar response to
the food being tested is compared with her/his response to 50g of pure glucose
(the reference food).
Foods which produce high blood-sugar levels after consumption will have a high
GI factor which means they will produce a high peak and will maintain a higher
blood-sugar level for longer.
Why is it Important to Know the GI Factor of the Food we Eat?
Food with a low GI factor will promote slow digestion and a gradual and steady
rise and fall in blood-sugar levels for people with diabetes. This is also beneficial
to people who do not have diabetes as a stable blood-sugar level reduces the
secretion of the hormone insulin over the course of a day. Slower digestion
also helps to delay hunger pangs and promote weight loss.
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