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What is the Glycemic Index?

The glycemic index (GI) is a system of measuring how fast a food or drink can trigger a rise in your blood sugar level. The higher the number, the greater the blood sugar response. The GI measures carbohydrate containing foods only. This is because fat and protein cause very little change in blood sugar levels.

A low GI food will cause a small rise in blood sugars levels, whilst a high GI food will trigger a more dramatic spike. The index is a numerical value, and compares each food type to glucose or white bread, which is rated at 100.

A GI of 70 or more is classified as high

A GI of 56 to 69 is medium

A GI of 55 or less is low.

Eating foods that are high on the Glycemic Index can lead to elevated blood sugar and insulin levels, which in turn can lead to a cascade of other problems such as obesity, hypertension and undesirable LDL and triglyceride levels.

What about simple and complex carbohydrates?

The GI varies greatly to the old theory regarding simple and complex carbohydrates. Simple carbohydrate are things like table sugar, white bread and lollies. Complex carbohydrates are things such as fruits, potatoes and wholegrains.

Complex carbohydrates were once believed to lessen the impact on blood sugar levels by being digested slower. New research is indicating that this is simply not the case, and complex carbohydrates behave in much the same way as simple carbohydrates.

The glycemic index and a low carbohydrate diet.

The glycemic index is useful in helping choose a carbohydrate food that will have a relatively low impact on your blood sugar. But remember, when following a low carbohydrate or ketogenic diet your total carbohydrate intake is of ultimate importance. If you want to stay in ketosis, it is the total grams of carbohydrate that are going to affect your ketosis levels, not its GI.

What factors affect the glycemic index of a food?

There are many factors that affect the GI of a food such as:

* Combining protein and fat with carbohydrates – this lowers the overall GI of the meal. Protein and fats delay stomach emptying and the digestion of starches.

* Ripeness – the riper the food the higher the GI (e.g. yellow/black bananas have a higher GI than green ones)

* Fibre – soluble fibre such as psyllium husks, oat bran, fruit pectins and legume fibres slows down the digestion of starches and the absorption of glucose into the bloodstream.

* Acidic foods – tend to slow digestion and decrease the overall GI of a meal, e.g. lemon juice sprinkled over vegetables, vinegar-based dressings, pickled foods.

* Processing – the more processed and refined the food, the higher it’s GI. Foods which have more “substance” as far as texture and fibre is concerned tend to take a lot longer to digest and thus have a slower impact on blood sugar levels.

* Salty foods – tend to speed the rate of digestion of starches.

Low GI foods are generally more filling, they help to control hunger and as well as blood sugar levels.

How is the glycemic index of a food determined, and why don’t the Empower Foods products have a GI rating?

To determine the GI of a food, a test person is required to eat a sample of food that contains 50g of carbohydrate. Their blood sugar levels are then analysed over a certain period of time.

50g of carbohydrate is found in the following:

2 slices of bread

500ml of soft drink

4 Tim Tams

25 cups shredded cabbage

1 kilo of carrots

3.5 kilos fresh mushrooms

24 Empower Foods Chocolate Rush Muffins

24 serves of Empower Foods FibreX Cereal

62 tablespoons Empower Foods LC Satay Sauce

From the above examples it is obviously easier to test the GI of higher carbohydrate foods, but nearly impossible to test low carbohydrate foods.

Anyone who has tried the Empower products would understand just how satisfying one serve is. No-one would physically be able to consume 24 serves in able to get a test result. I think the researchers would have a near impossible task ahead of them in getting their test subjects to eat 1 kilo of carrots, or 24 Empower muffins in one sitting!

Having said that, because of the extremely low carbohydrate levels in the Empower products, they would all be treated as “low glycemic”.

Serving size is still important.

It is important to consider the amount of a food you are eating. If a food has a medium to high GI, but is not ordinarily consumed in large quantities then the value of the GI is not an issue. In contrast, if it is normally consumed in large quantities then the GI and total carbohydrate consumed is of concern.

“The total amount of carbohydrate is more important than the source or type; the GI may reduce post-meal blood glucose, but studies do not show sufficient evidence of long-term benefit for it to be recommended." American Diabetes Association, January 2002.

To use pasta as an example: even though pasta has a low GI it is not advisable for people with diabetes or impaired glucose tolerance to have a large serve because the total amount of carbohydrate they will eat will be far too high.

The glycemic load – a much better way!

The glycemic load (GL) is a relatively new way to assess the impact of carbohydrate consumption on our blood sugar levels. It takes the GI of a food into account, but gives a much fuller picture than just looking simply at the GI alone. The GL is the best way to choose foods that are both low in carbohydrate and low on the glycemic index.

A GI value only tells you how rapidly a particular carbohydrate turns into sugar. It doesn't tell you how much of that carbohydrate is in a serving of a particular food. You need to know both things to understand a food's effect on blood sugar. That is where GL comes in.

A GL of 20 or more is high

A GL of 11 to 19 is medium

A GL of 10 or less is low.

Foods that have a low GI will have a low GL. Foods with a high GI range will from a very low to very high GL. Therefore, you can reduce the GL of your diet by limiting foods that have both a high GI and a high carbohydrate content.

How to calculate the glycemic load of a food.

The GL is the GI in decimal (eg. A GI of 72 becomes .72) form multiplied by its available carbohydrate content in grams.

For example: Watermelon.

Its GI is 72. In a serving size of 120 grams it has 6 grams of available carbohydrate per serving, so its GL is pretty low, around 4. (.72 x 6 = 4.32 )

Remember to consider the glycemic load of all foods and drinks

Thus, the GI should not be your only criterion when selecting what to eat. The GI is most useful when deciding which high-carbohydrate foods to eat. But don't let it lull you into eating more carbohydrates than your body can handle.

The number of grams of carbohydrate we consume is awfully important. Make sure you know the carbohydrate content of the foods you eat - study the nutritional information on the package.

For a comprehensive listing of many common foods and their GL and GI go to http://diabetes.about.com/library/mendosagi/ngilists.htm