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Glycemic Index FAQ

What is blood glucose?
Glucose (also known as dextrose) is the main sugar in the blood, and is commonly referred to as blood sugar. It is the main source of energy in the body and is obtained from food or made by the liver. Glucose is made from all three elements of food, protein, fat and carbohydrates, but in largest part from carbohydrates. It is carried to each cell through the bloodstream although the cells cannot use the glucose without the help of insulin.

What is glycogen?
Glycogen consists of branched chains of glucose and it is how glucose is stored in the body.

Where is glycogen stored?
Glycogen is mainly stored in the liver and skeletal muscle.

What is glycogenolysis?
Glycogenolysis is the process whereby glycogen is broken down into glucose, a process that occurs when the body requires energy.

What is insulin?
Insulin is a natural hormone made by the pancreas that controls the level of the sugar glucose in the blood. Insulin permits cells to use glucose for energy without it glucose cannot be utilised. Insulin stimulates skeletal muscle fibers to take uo glucose and convert it to glycogen. It also stimulates liver cells in the uptake of glucose from the blood and convert it to glycogen and inhibits production of the enzymes involved in the break down of glycogen.

What is the Glycemic Response?
Glycemic response is the effect of food, after consumption, on the blood glucose levels over a period of time.

What is the Glycemic Index?
The Glycemic Index is a system that ranks foods based on the rate at which ingested food will increase blood sugar levels. This scale is relative to Glucose. A high glycemic index gives a rapid rise in blood sugar levels and a low glycemic index gives a slow increase in blood sugar levels.

What food has the highest Glycemic Index?
Pure glucose has the highest Glycemic Index ranking of 100 and all other foods are ranked in relation to glucose.

Are simple and complex carbohydrates an alternative description to glycemic index?
Generally no, the process is more complex than this. Carbohydrates can be classified as simple or complex based on the number of simple sugar units in the molecule. Carbohydrates composed of one or two simple sugars like fructose, sucrose and glucose are generally referred to as simple, while starchy foods were labeled complex because starch is composed of longer chains of sugars. However fructose has a low glycemic index of around 20, sucrose has a medium glycemic index of around 70 and glucose has a high glycemic index of 100. This means that the blood glucose levels are effected very differently for simple carbohydrates, the same is true for complex carbohydrates.

Do simple carbohydrates have a high Glycemic Index?
Not necessarily, fructose is a simple cabohydrate with a low glycemic index. Sucrose is a simple carbohydrate with a medium glycemic index.

How do you measure the Glycemic Index?
Volunteers are typically given a test food that provides 50 grams of carbohydrate and a control food of pure glucose (sometimes white bread is used) that provides the same amount of carbohydrate on different days. Blood samples are taken prior to eating and at regular intervals after eating over several hours. From the blood samples, the amount of blood glucose is measured and plotted over time. The glycemic index is calculated as the area under the glucose curve after the test food is eaten, divided by the corresponding area after the control food is eaten. The value is multiplied by 100 to represent a percentage of the control food.

What factors effect the Glycemic Index?
Processing (puffed cereals have a much higher GI than the grain they came from), ripeness of fruit (unripe bananas can have a GI of 43, where overripe ones have been clocked at 74), protein content (soy beans have a lower GI than other beans), fat content (peanuts have a very low GI), fiber (orange juice has a higher GI than oranges), and how small the particles are (whole grains have a relatively low GI, but grinding them into flour shoots up the GI). In addition to this, other factors such as the ratio of carbohydrates to fat and protein as well as how the food was cooked (eg. Boiled compared to fried or baked) and metabolism will determine the way your body’s sugar level responds after eating.

What is the Glycemic Load?
The glycemic index compares the potential of foods containing the same amount of carbohydrate to raise blood glucose. However, the amount of carbohydrate consumed also affects blood glucose levels and insulin responses. The glycemic load of a food is calculated by multiplying the glycemic index by the amount of carbohydrate in grams provided by a food and dividing the total by 100. In essence, each unit of the glycemic load represents the equivalent blood glucose-raising effect of 1 gram of pure glucose (or white bread).

What is the Dietary Glycemic Load?
Dietary glycemic load is the sum of the glycemic loads for all foods consumed in the diet. The concept of glycemic load was developed by scientists to simultaneously describe the quality (glycemic index) and quantity of carbohydrate in a meal or diet.

Can you give me general rules to follow?
Increase the consumption of whole grains, nuts, legumes, fruits and nonstarchy vegetables. Decrease the consumption of starchy high-glycemic index foods like potatoes, white rice and white bread. Decrease the consumption of sugary foods like cookies, cakes, candy and soft-drinks.

Is the Glycemic Index the same for different people?
The body's response to food will relate to several factors including; age, activity level, insulin levels, time of day, amount of fibre and fat in the food, how refined (processed) the food is, and what was eaten with the food.


 
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