The glycemic index is a table of measurements which tells how quickly food will be converted by the body into blood sugar (blood glucose). If a food is low on the glycemic index, it will take a long time to convert to blood sugar. A food high on the glycemic index quickly becomes glucose.

The glycemic index uses pure glucose as the food against which all others are measured. Glucose is given a score of 100 on the glycemic index, so keep that in mind when you hear the value of other foods. Surprisingly, some foods, such as dried dates, score higher than pure glucose. (Dried dates rank 103.)

The glycemic index is important because foods which are slowly digested help you stay fuller longer and keep your blood sugar stable. If you eat something high on the glycemic index, such as instant mashed potatoes (86), you will experience a rapid spike in blood sugar followed by an equally rapid sharp decline. This blood sugar roller coaster can lead to chronic exhaustion and overeating. Erratic blood sugar levels can also stress the body and make it more susceptible to developing diabetes and other diseases.

For people with diabetes, the glycemic index is probably the single most important food measurement to take into consideration. Eating foods low on the glycemic index and stabilizing blood sugar naturally can help diabetics decrease or even eliminate the need for insulin shots. If you are worried about developing diabetes, learning the glycemic index can be one of the best preventive measures you can take. (Read the article, How Learning the Glycemic Index Saved My Life.)

For weight watchers, the glycemic index is also critical. This is because foods low on the glycemic index help you eat less overall. The slow digestion process keeps you from feeling hungry. Keeping your blood sugar stable will also help your body digest the food properly instead of immediately converting it into fat.

A lot has been written over the years about food and its effects on blood sugar. Unfortunately, much of the information has been inaccurately presented. As important as the glycemic index is for your health, it has been misconstrued, misrepresented and misunderstood, often by popular diet books. The glycemic index is not difficult to understand but nonetheless, misinformation about it is everywhere.

Many people have the mistaken idea that table sugar and blood sugar are equivalent and that foods with lots of table sugar are automatically high on the glycemic index. This is not true. Table sugar and blood sugar are entirely different on a molecular level. Table sugar is sucrose and blood sugar is glucose. On the glycemic index, glucose is rated at 100 and sucrose is rated at 65.

Ice cream is incredibly high in table sugar but only has a rating of about 50 (depending on the exact kind) on the glycemic index. Why is this? It's because ice cream is also high in cream, milk and eggs. All of those ingredients are so low on the glycemic index that the addition of sugar is not enough to raise the overall glycemic index.

The fact that foods are rarely eaten alone is one of the things that makes the glycemic index confusing. If you eat a food high on the glycemic index along with foods that are low, (such as the sugar along with the cream and eggs in the ice cream) it is the average of all the foods eaten together that counts. So if you really want that piece of cake, have a glass of milk too and the glycemic index is greatly reduced.

Another fact you might find shocking is that many foods sold as "sugarless" actually contain sweeteners that are higher on the glycemic index than pure glucose! This makes these foods worse than worthless; it makes them dangerous. For example, a low fat, sugarless frozen tofu desert, promoted as a healthy alternative to ice cream, has a glycemic index rating of 115.

To really get an accurate idea of where a food ranks on the glycemic index, please check out the Glycemic Index List. This list was compiled by researchers who carefully monitored the blood sugar reactions of people given foods in isolation on an empty stomach. Their individual reactions (which will vary a bit) were then averaged together. This is the most accurate way to measure the glycemic index.