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A joint consultation report of the World Health Organization and the Food and Agricultural Organization of the United Nations suggests to use the glycemic index (see below) in diabetes meal planning. The study recommends that in choosing carbohydrate foods in your diet and to estimate how these foods will affect your blood sugar, you may use the glycemic index as a useful indicator, especially in management of diabetes. Research is also showing that eating a low glycemic diet helps reduce the risk for heart disease.

WHAT THE  GLYCEMIC INDEX IS?
Glycemic index (GI) is a measure that ranks carbohydrate foods how quickly and intensely they will affect your blood sugar when you eat these foods. The underlying concept of the glycemic index is that different foods take different times to break up in the digestive process and release sugar into the bloodstream; some foods are quick- absorbing and break up quickly, while others are slow-absorbing and take a longer time to be digested.

The foods that break up quickly as sugar into the bloodstream have a high glycemic index. In contrast, foods that absorb slowly have a lower glycemic index. Generally, high glycemic foods raise blood sugar more quickly and more intensely than the low glycemic foods. Because carbohydrate is the only group of foods that causes maximum rise of blood sugar (protein and fat do not directly affect blood sugar), glycemic index has been developed for carbohydrate foods only. Even different foods under the carbohydrate group have different ratings on the glycemic index because they vary in the speed in which they release sugar into the bloodstream. Carbohydrate foods that are coarse, unrefined, and contain fiber have a lower GI than their refined varieties. A whole wheat bread, for example, has a lower GI than a white bread made of refined flour. Because fat slows down the absorption of food into the bloodstream, carbohydrate foods, containing high content of fat, take longer time to be absorbed in the blood and are stated to have a low GI. (But foods with high fat content may be harmful.) Glycemic index tables have been prepared for a large number of foods. A glycemic index adapted from the Food and Agricultural Organization/ World Health Organization  Expert Consultation Report on Carbohydrates in Human Nutrition (1997) is shown in the tables below.

GLYCEMIC INDEX IN MANAGEMENT OF DIABETES
The glycemic index has significant application in management of diabetes:

Blood Sugar Control
Carbohydrates are mainly responsible for raising blood sugar.  Glycemic index is based on the principle that all carbohydrates are not equal, and the foods having high glycemic index values release sugar more quickly in the bloodstream than foods with low values on the glycemic index. When you eat foods with high glycemic index values such as white bread, white rice, most potatoes, or other foods made with refined grains, they digest rapidly and you tend to have a rapid and intense rise of blood sugar. These spikes in blood sugar overstimulate your pancreas to give a burst of insulin to level off the raised blood sugar levels. Such sudden and rapid swings in blood sugar and insulin levels have been shown to contribute to the development of type 2 diabetes and heart disease. In contrast, low glycemic index foods such as whole grain foods, including coarse bread, whole grain pasta, whole grain cereals, brown rice, and beans that are high in fiber, are slowly absorbed in the digestive process. As a result, you are likely to have a slow and smooth rise of blood sugar.

Gradual increase of sugar in the blood is of crucial significance, especially for people with type 2 diabetes whose bodies do not produce enough insulin or the insulin they produce does not work effectively. The available insulin in these people can handle a gradual rise (in contrast with rapid rise) of blood sugar in a better way, helping keep steady control of blood sugar.

Controlling Triglycerides
High blood sugar is a major cause of raised triglycerides in diabetes, which in turn heightens your risk for developing heart disease. Because a low glycemic diet helps control your blood sugar, blood triglycerides also improve in parallel, resulting in reduced risk for heart and blood vessel diseases. In addition, evidence shows that a low glycemic index diet rich in fiber has a triglyceride lowering effect, a factor that reduces the risk for related chronic diseases.

Weight Control
Excess body weight heightens the risk for developing type 2 diabetes. In people with preexisting diabetes, excess weight increases the chances of developing long-term complications. Low GI foods, however, help control your weight and reduce the risks for diabetes complications. How the low GI foods are helpful in weight reduction? The explanation is:

When you eat fast-absorbing foods (foods made of refined grains or potatoes, for example), your blood sugar rises rapidly and intensely, and your pancreas releases a burst of insulin to bring down raised blood sugar levels. Although insulin by itself does not make you fat, it does store excess sugar (produced from your overeating) as fat in your body. Such a fat storage leads to unhealthy weight gain. When, on the other hand, you eat low GI foods, they slowly break up into sugar in your digestive process and do not raise your blood sugar as rapidly as the foods with high GI. When blood sugar does not rise abruptly, the body does not release excess insulin, and you are protected from its side effect of piling up of fat and the resulting unhealthy weight gain.

Meal Planning
Glycemic index can be an important tool in meal planning. As noted just now, people with type 2 diabetes can be in a better position to control blood sugar and prevent it from rising abruptly when they include slow-absorbing or low glycemic foods in their meals. Glycemic index is also relevant in meal planning for people with type 1 diabetes and those who take insulin injections to control their blood sugar. When these people include fibrous or slow-absorbing carbohydrates in their meals, they inject less insulin because of the increased fiber content of these foods.

Note, however, that all low glycemic foods may not necessarily be the best choices, nor all high glycemic foods are necessarily bad in all situations. Some low glycemic foods (such as whole milk) may have high fat content, which you may need to avoid. On the other hand, some high glycemic foods may be low in calories and rich in other nutrients and may be good food choices.

Although low glycemic foods may be generally preferable, they are not suitable when you are in need of immediate uptake of energy such as after a strenuous activity or in an emergency condition when you are experiencing low blood sugar. In such situations, high glycemic foods (such as glucose) are the right choice because such foods will raise your blood sugar quickly and correct low blood sugar events in a faster way.

A good choice in diabetes meal planning might be to fill the major part of your carbohydrate allowance from carbohydrate foods with low glycemic index values. This approach, however, has a problem: choices from slowabsorbing carbohydrate foods are limited, and building a meal plan on this approach will deprive you of the variety of foods (Variety of foods is an essential part of healthy eating.) The right choice, therefore, is to include slow-absorbing carbohydrate foods in your meals sensibly. The Eat-Right Model will help you make the sensible food choices.

GLYCEMIC INDEX HELPS REDUCE THE RISK OF HEART DISEASE
Diets rich in whole grains, which have low GI, have clearly been shown to achieve healthier levels of blood sugar, cholesterol, homocysteine, and reduction in inflammatory cells in the body. All these outcomes are associated with a healthier heart and a reduced risk for heart disease. Such diets include bran, whole wheat, fruits and vegetables, which are rich in fiber, vitamins, minerals, and antioxidants.

A research study reported in the Harvard Medical School Guide to Healthy Living estimates that eating a bowel of cold breakfast cereal every day (that provides about 5 grams of fiber) reduces the risk for heart disease by nearly one-third. A list of select foods with their content of dietary fiber is shown in the Table. A study published in the American Journal of Clinical Nutrition has reported that women whose diets were an average 10 point less GI (60 instead of 70) lowered their risk for heart disease. This benefit could be achieved because this diet raised HDL (good) cholesterol, reduced total cholesterol, LDL (bad) cholesterol, apolipoprotein B, and lowered insulin resistance. The heart health benefits of whole grain diets have further been confirmed by another study recently published in the American Journal of Clinical Nutrition. The study, after examining the diet records and blood samples of about 1,000 healthy middle-aged adults, found that people who consume diets rich in whole grains such as whole wheat and bran, fruits, and vegetables have healthier levels of blood sugar and cholesterol. The researchers discovered that people whose intake of whole grain foods is high, gain less weight and their total cholesterol and LDL (bad) cholesterol are less than the persons who consume a smaller amount of whole grains. Thus, eating whole grain foods has been found to be associated with reduced risk for heart disease.

HOW THE GLYCEMIC INDEX IS DEVELOPED
You might be interested to know how the glycemic index is developed. Glycemic index, as noted before, is built for carbohydrate foods. Researchers develop the glycemic index in four parts, and then follow a specific procedure to determine the index values of foods:

• First, a reference food containing 50 grams of carbohydrate is selected, against which glycemic index of other foods (test foods) will be determined. Reference food can be either a white bread or glucose dissolved in water. Researchers often prefer white bread because it is generally easier to eat the bread than to drink large amounts of glucose.

• Second, the researchers measure how much blood sugar rises in a volunteer by eating the white bread or drinking glucose, containing 50 grams of carbohydrate. The blood sugar response from either the white bread or glucose (reference food) is taken as a reference value.

• Third, blood sugar increase from eating a test food, containing 50 grams of carbohydrate, is measured.
• Fourth, blood sugar response to the test food is divided by blood sugar response to the white bread or glucose. The result is the glycemic index of the test food.

PROCEDURE FOR DEVELOPINGTHE GLYCEMIC INDEX
To develop the glycemic index, a typical procedure is followed. Assume the researchers aim to determine the glycemic index of cornflakes (test food) with reference to white bread (reference food). They will adopt the following procedure:

• A volunteer, after overnight fasting, eats about 100 grams of white bread that contains 50 grams of carbohydrate.

• Fingerstick blood samples are taken at the intervals of 15, 30, 45, 60, 90, and 120 minutes after eating the white bread.

• Blood sugar in each sample is measured and the test results are recorded.

• The next step is to get the mean value of all the test results. The mean value is derived through mathematical calculations. This value indicates, how much on the average, the 50- gram carbohydrate in the white bread has raised blood sugar in the volunteer.

• Blood sugar responses in a person vary from day to day. To account for these variations and to derive a representative value, blood sugar responses to the white bread are checked in the same volunteer on 2 to 3 different occasions or different days. The average value of all the test results is calculated. This value represents the mean glucose response of the reference food in the volunteer.

• To derive blood sugar response to the reference food (white bread) on a wide basis, the above testing process will be repeated in six or more volunteers and the test results in all the volunteers will be averaged. The final average reading of all these blood sugar values will be the glycemic index of the white bread against which the glycemic index of all other test foods will be expressed as percentages.

• Now, to determine the glycemic index of cornflakes, 2 cups of cornflakes (test food) that contain about 50 grams of carbohydrate, will be given to the volunteer for eating. Blood samples will be drawn and blood sugar will be measured adopting the same procedure as followed above in testing the reference food (white bread). Blood sugar responses of the volunteer from eating the cornflakes will be averaged.

• To calculate the glycemic index of cornflakes, blood sugar response to the cornflakes is divided by blood sugar response to the white bread.

• To develop a broad-based glycemic index, this process of testing will be repeated in more volunteers, and test results in each volunteer will be averaged and recorded. All these averages will be added together and then the overall average will be derived. This final average value will represent the glycemic index of a test food, cornflakes in the present example.

GRADING THE  GLYCEMIC INDEX
Glycemic index (GI) with reference to white bread may be graded as:

• Low GI: Less than 75

• Intermediate GI: 75 to 96

• High GI: Greater than 96

When consulting the glycemic index tables, always make sure what is the reference food of the index: white bread or glucose. GI expressed with reference to white bread is 1.38 times greater than GI based on glucose.

Glycemic index, as a part of meal planning, is a useful tool in planning healthy meals, managing blood sugar, and reducing the risk for heart disease. Follow the Eat-Right Model that incorporates low glycemic foods such as whole grain foods, beans, vegetables, and other high fibrous foods as the important ingredients in meal planning.