DISCLAIMER: THIS PAGE CONTAINS A GENERAL EDUCATIONAL DISCUSSION ON THE ABOVE TOPIC. IT IS NOT HEALTH ADVICE AND SHOULD NOT BE CONSTRUED AS SUCH. YOU SHOULD NEVER RELY UPON THE INFORMATION GIVEN HERE. YOUR PARTICULAR CIRCUMSTANCES MAY WELL REQUIRE AN ENTIRELY DIFFERENT APPROACH. YOU SHOULD NOT MAKE ANY CHANGES IN YOUR MEDICATIONS, DIET, ACTIVITY, LIFESTYLE, ETC. WITHOUT FIRST CONSULTING A LICENSED PHYSICIAN IN YOUR AREA.
Carbohydrates are sugars and starches. Sugars are also called simple carbohydrates while starches are also known as complex carbohydrates. Starches are simply many sugar molecules joined together into one very large molecule. Starches are broken down into their constituent sugars molecules in our mouths and intestines. The sugar molecules are then absorbed by the intestine into the blood stream.
In response to the absorbed sugar in the blood, our pancreas secretes insulin into the blood and other hormone levels change as well.
Certain carbohydrates raise the blood sugar level more than others, even in non-diabetics. The glycemic load is a measure of how much a given carbohydrate source can elevate the blood sugar level.
Foods with a high glycemic index release their sugar into the bloodstream faster than foods with a lower glycemic index. The glycemic load is the glycemic index of the food multiplied by the total amount of carbohydrate it contains. The glycemic load is therefore a measure of the increase in blood sugar levels following a meal.
As a broad generalization, simple carbohydrates (sugars) have a higher glycemic index than complex carbohydrates (starches). However, exceptions to this rule exist. Some complex carbohydrates (starches) have a higher glycemic index than some of the simple carbohydrates.
When starchy foods with a high glycemic index are eaten, they are digested into sugar molecules rapidly and the sugar molecules are absorbed rapidly into the blood, resulting in high sugar and insulin levels. Conversely; low glycemic index starchy foods are digested and absorbed slowly, resulting in lower sugar and insulin levels.
So, a higher glycemic index means that food raises the blood sugar more than a food with a lower glycemic index. Eating foods with a high glycemic index may have a number of deleterious effects. These may include lower levels of the good (HDL) cholesterol, higher triglyceride (fat) levels, resistance to the effects of insulin, increased appetite, less fat burning, weight gain and more coronary artery disease.
A complete list of the glycemic index of various foods can be found at the bottom of this page. A helpful web site is Glycemic Index On-Line.
Many people divide up foods into low glycemic index foods and high glycemic index foods. It is more helpful to divide them up into four levels of glycemic index. In general, foods with pure sugar have a very high glycemic index. Potatoes, carrots and refined grain products such as pasta, white rice, and white bread are the next highest. Unrefined grain products such as brown rice and whole grain breads and cereals have a lower glycemic index. Fruits and vegetable other than carrots and potatoes gave the lowest glycemic index.
Adding fiber to any meal slows the absorbtion of sugar and hence lowers the glycemic index of the meal.
Eating an ultra low fat diet (less than 10% of calories from fat) means that the remainder of the calories must come from carbohydrates. Possibly due to the high glycemic index of some of the carbohydrates eaten in these diets, these ultra low fat diets are paradoxically associated with high triglyceride and low HDL cholesterol levels as well as other metabolic abnormalities. These facts have led to many experts recommending that fat intake not be cut so drastically. They prefer that fat account for 25% to 30% of the total calories. Such a diet is also much easier for the average person to stick with in the long term than the ultra low fat diet is. Furthermore, scientific studies have not shown any benefit in terms of protecting against heart disease by lowering fat intake below 25% of the total calories eaten.
Advocates of the ultra low fat diet counter that, despite the above facts, their patients have a very low incidence of heart disease. Furthermore, patients with established atherosclerosis seem to have regression of the atherosclerosis and improved blood flow to their heart as a result of the ultra low fat diet.
One scientific study compared a low fat diet (18% of calories from fat) with no restrictions on the types of carbohydrates eaten to a diet with 30% fat but restricting carbohydrates to those with a low glycemic load. Several interesting discoveries were made. People eating the low fat diet demonstarted a slowing of their metabolism. This is a common problem with many diets. It impedes the ability to continue to lose weight. Remarkably, this slowing of the metabolism was not seen in people eating the low glycemic load diet. People in the low glycemic load group reported less hunger too. The low glycemic index diet also led to less insulin resistance (which should help ameliorate or prevent diabetes), lower triglyceride levels, lower blood pressure and lower levels of inflammatory proteins in the bloodstream. However there was no significant difference in weight loss or total body fat between the two groups.
As of the date of this writing, this dispute among varying diets has not been resolved. Further scientific studies are needed.
Many authorities do not feel that the glycemic index is of value. The reason is that the glycemic index of a food can be quite variable. It can vary based on many factors including how quickly the food is eaten, chewed and swallowed, how the food is prepared, other non-carbohydrate components of the food (for example, fiber in food lowers its glycemic index), other foods ingested with the meal and person to person variations in how their gastrointestinal tract digests and absorbs food.
Below are excerpts from an excellent study listing the glycemic indices (GI) and Glycemic loads (GL) of many food, followed by a table of their actual data. A GI is 70 or more is high, a GI of 56 to 69 inclusive is medium, and a GI of 55 or less is low. A GL of 20 or more is high, a GL of 11 to 19 inclusive is medium, and a GL of 10 or less is low.
International table of glycemic index and glycemic load values: 2002
Kaye Foster-Powell
From the Human Nutrition Unit, School of Molecular and Microbial Biosciences, University of Sydney, Australia
American Journal of Clinical Nutrition, Vol. 76, No. 1, 5-56, July 2002
© 2002 American Society for Clinical
Nutrition
The purpose of this revised table is to bring together all the
relevant data published between 1981 and 2001. For many foods there are 
2 published values; therefore, the mean
(±SEM) GIs were calculated and are listed underneath the data for the
individual foods. Thus, the user can appreciate the variation for any one food
and, if possible, use the GI value for the food found in their country.
Many people have raised concerns about the variation in published GI values for apparently similar foods. This variation may reflect both methodologic factors and true differences in the physical and chemical characteristics of the foods. One possibility is that 2 similar foods may have different ingredients or may have been processed with a different method, resulting in significant differences in the rate of carbohydrate digestion and hence the GI value. Two different brands of the same type of food, such as a plain cookie, may look and taste almost the same, but differences in the type of flour used, in the moisture content, and in the cooking time can result in differences in the degree of starch gelatinization and consequently the GI values. In addition, it must be remembered that the GI values listed in the table for commercially available processed foods may change over time if food manufacturers make changes in the ingredients or processing methods used.
Another reason GI values for apparently similar foods vary is that different testing methods are used in different parts of the world.
Although it is clear that GI values are generally reproducible from place to place, there are some instances of wide variation for the same food. Rice, for example, shows a large range of GI values, but this variation is due to inherent botanical differences in rice from country to country rather than to methodologic differences.
The GI values listed in the revised table represent high-quality data published in refereed journals or unpublished values generated by Sydney University's Glycemic Index Research Service, often as a result of contract research by industry. The foods have been described as unambiguously as possible by using descriptive data about the food given in the original publication. In some cases, descriptive details were extensive, including the species or variety of plant food, the brand name of the processed food, and the preparation and cooking methods. In other cases, the only description was a single word (eg, potatoes or apple). If the cooking method and cooking time were stated in the original reference, the details are given. The user should bear in mind that countries often have different names for the same food product or, alternatively, the same name for different items. For example, Kellogg's Special K breakfast cereal is a very different product in North America (Kellogg Canada Inc) than in Australia (Kellogg, Sydney, Australia), each of which has a different GI value. Similarly, food names may mean different things in different countries. For example, biscuits, muffins, and scones have different meanings in North America and in Europe. The terms used in the revised table have been selected to be as internationally relevant as possible.
Some research laboratories continue to use white bread as the reference food for measuring GI values, whereas others use glucose (dextrose); therefore, 2 GI values are given for each food. The first value is the GI with glucose as the reference food (GI value for glucose = 100; GI value for white bread = 70), and the second value is the GI for the same food with white bread as the reference food (GI value for white bread = 100; GI value for glucose = 143). When bread was the reference food used in the original study, the GI value for the food was multiplied by 0.7 to obtain the GI value with glucose as the reference food. The table lists the reference food that was originally used to measure the GI value of each food.
The foods in the table are separated into the following food groups: bakery products, beverages, breads, breakfast cereals and related products, breakfast cereal bars, cereal grains, cookies, crackers, dairy products and alternatives, fruit and fruit products, infant formula and weaning foods, legumes and nuts, meal-replacement products, mixed meals and convenience foods, nutritional-support products, pasta and noodles, snack foods and confectionery, sports bars, soups, sugars and sugar alcohols, vegetables (including roots and tubers), and indigenous or traditional foods of different ethnic groups. Within each section, foods are arranged in alphabetical order by common name. This classification of the foods was made on a practical rather than a scientific basis. There are no GI values given for meat, poultry, fish, avocados, salad vegetables, cheese, or eggs because these foods contain little or no carbohydrate and it would be exceedingly difficult for people to consume a portion of the foods containing 50 g or even 25 g of available carbohydrate. Even in large amounts, these foods when eaten alone are not likely to induce a significant rise in blood glucose.
Both the quantity and quality (ie, nature or source) of carbohydrate influence
the glycemic response. By definition, the GI compares equal quantities of
carbohydrate and provides a measure of carbohydrate quality but not quantity.
In 1997 the concept of GL was introduced by researchers at Harvard University
to quantify the overall glycemic effect of a portion of food (7–9). Thus, the GL of a typical serving of food is the product of
the amount of available carbohydrate in that serving and the GI of the food.
TABLE 1 International table of glycemic index (GI) and glycemic load (GL) values: 20021
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