Prior to 1981, if a patient was informed they had diabetes the patient would be given a diabetic exchange list of foods to eat, along with portion sizes. The exchange system is divided up into three main categories: carbohydrates, proteins and fats. A change to the system was that a 1/2 cup of pasta was considered a serving but now it is 1/3 cup of pasta per serving. The carbohydrate group consists of starch, fruit, milk, vegetables and all other carbohydrates. The meat section is divided into very lean, lean, medium and high fat meats. The fat group includes all fats. The exchange system was standardized throughout the country and taught in hospitals, private practices, and in schools.
In the early 1980′s, a professor named Dr. David Jenkins, PhD., was interested to know why some foods raise blood sugar levels higher than other foods. At that time he took a pre-measured amount of food and gave it to patients; after the food was consumed the blood sugar levels were monitored. All types of food were monitored such as white bread, ice cream, corn, carrots and watermelon to name a few.
When other scientists heard about the initial results, many other researchers tried the same format. Currently there are thousands of foods listed on the glycemic index (G.I.). For example, low G.I. foods are spaghetti and peas, whereas high G.I. foods are mashed potatoes and sticky rice. However, they are all complex carbohydrates. When discussing the glycemic index it is measured by the sugar release into the blood stream.
Glycemic index levels are generally categorized as: low, medium or high, depending on how high the blood sugar level was raised after consumption of a single food item. Below is an example of a list of foods of different levels. There are books that have complete lists of foods with glycemic index levels as well as lists that can be found on-line.
Foods that have a low G.I. are dried beans and legumes. Examples of these are: kidney and lentils.
Low G.I. foods are rated: 0 to 55
- Peanut butter 14
- Pasta 44
- Baked beans (canned) 48
Intermediate or medium G.I. foods are: 56 to 69
- Raisins 56
- Instant oatmeal 66
- Pancakes 67
High G.I. foods are: 70 or more
- Bagel 72
- Cheerios 74
- Pretzels 83
- Cornflakes 92
Meats and fats do not have a glycemic index because they do not contain carbohydrate. Fiber tends to lower the glycemic index of foods.
There are other factors that can change a glycemic level such as the ripeness of a piece of fruit. The riper the fruit the higher the glycemic number, a cup of juice will have a higher glycemic level than a piece of fruit. A mashed potato will have a higher G.I. than a baked potato. When preparing pasta, if it is soft and mushy the index higher than if it prepared al dente.
Remember the glycemic index is a measurement of a food eaten alone. Therefore carrots eaten alone have a higher index then eaten with meat and a baked potato.
When working with clients that have diabetes, not all of them will be familiar in working with glycemic index foods, some continue to use the exchange system; some clients will have changed to a point system and those who have type II diabetes may just stay away from sugary foods such as cookies, cakes, pies and candy. Other clients may work with a carbohydrate counting system. Many professionals use this system when working with children (it is easy to work with school district nurses and cafeterias) and newly diagnosed adults.
Dr. Jim Bell