Glycemic Index (GI) is a system that ranks carbohydrate rich foods on a scale from 1 to 100 based on how the foods raise the total blood-glucose levels (blood-sugar levels) after being eaten, broken down into their simplest forms, absorbed in the small intestines and transferred to the bloodstream. Glucose is the simplest form of sugar found in the blood. It’s also referred to as blood sugar and should normally be maintained at a level of
Absorption of Glucose
Supposing you ate pure glucose, which is a simple sugar, it would be absorbed, within 15 minutes, into the bloodstream.. This would result in a rise of blood sugar level at a faster and higher rate than other foods, like beans or pasta. Glucose is given the highest Glycemic Index (GI) rating of 100.
Supposing you ate Chickpeas, which is made up of complex carbohydrates, which would have to be broken down into simple sugars first, before being absorbed in the small intestines and into the bloodstream. It would take more time to raise the blood glucose level. Chickpea is given a Glycemic Index (GI)rating of about 28.
In general, the presence of fibre, protein and fat in a particular food, also slows down the digestion process and absorption of glucose into the bloodstream.
- White bread has a GI ranking of 70;
- Table sugar (sucrose), GI of 68;
- Brown rice, GI of 55;
- carrots, 47;
- Apples 38 and
- Peanuts, 14, just to mention a few.
Glycemic Index (GI) Scale
Low Glycemic Index Foods:. These are foods with a GI of up to 55. Examples are foods like: steel cut oats, pasta, apple, milk and sweet potatoes.
Medium Glycemic Index Foods: These are foods with a GI of 56-69.. Examples are wholegrain breads, brown rice, basmati rice, quick oats, and cantaloupe.
High Glycemic Index: Foods: These are foods with a glycemic index of 70-100., These include: dried dates, potatoes, white breads, instant oats and mostly processed foods.
Effect of High Blood Glucose Levels
Any time the blood sugar rises above the required amount, the beta-cells in the pancreas will be triggered to release insulin, which will instruct your body to either burn the excess glucose or remove them from the bloodstream into the cells or convert them into glycogen and store them in the liver and muscles for future use. Excess insulin secretion can result in fatigue, weight gain and, eventually, type 2 diabetes.
How Fast is Glucose Absorbed?
Any pure glucose that is present in the food you eat, will be absorbed into your bloodstream within fifteen minutes.
Other carbohydrates will require digestion, before absorption. Those that digest quickly–the so-called “high glycemic carbs” like white bread or sugar–typically take between a half hour and an hour to enter your bloodstream.
Slower acting carbohydrates like whole grains or pasta may take an hour to two, and in the case of some hard-wheat pastas, three hours to release their glucose into your bloodstream.
Points to Note:
- After eating a meal, the concentration of glucose in your blood will begin to rise as the food is digested and the glucose is absorbed into your bloodstream. But in a healthy body, this rise is brief and not very high.
- Blood Glycemia means how much glucose there is in the blood.
- Your brain requires a small but steady supply of glucose at all times and will stop functioning if it doesn’t get it.
Digestion and Absorption
- Glycemic Index
- Glycemic Indexes Do Not Depend on Glucose Absorption Speed
- Glycemic index and glycemic load for 100+ foods
- Getting to know the Glycemic Index
- Glycemic Index database
- What is blood sugar? What is blood glucose?
- Blood sugar levels and fluctuations
- How the body control glucose