A Diabetic's Guide to Glycemic Index

The glycemic index is a powerful tool for diabetics, but in order to use it effectively, it must be understood. Most diabetics know that carbohydrates are in some way responsible for weight gain, and directly affects their blood sugar levels. The glycemic index, and glycemic load can make understanding how they impact health easy.

When food is consumed, the body breaks it down so that it can be absorbed. All of the carbohydrates and approximately 40% of the proteins are converted into glucose. Glucose is picked up, along with nutrients, from the digestive tract and transported to the liver. The liver filters the blood that is transporting the nutrients to remove toxins and bacteria before it is distributed throughout the body. Glucose is converted to glycogen, a compact form of energy, and is stored in muscle tissue, the brain and major organs. Glycogen provides energy for the cells, enabling them to function. Some of the glucose is converted into triglycerides and stored in the liver, the balance is stored in the adipose tissue as belly fat.

Different foods break down at different rates. Some enter the bloodstream over a period of time and have a lesser probability of causing blood sugar spikes. Others breakdown and enter the bloodstream quickly, and will cause blood sugar spikes. Those that breakdown slowly and enter the bloodstream gradually over time are low glycemic index foods. Those that enter the bloodstream quickly are high glycemic index foods. The blood sugar spikes they cause are commonly followed by a crash.

Lower glycemic index foods are less likely to raise the blood sugar levels that result in the over production of insulin in type II diabetics. Or, it could result in the taking larger amounts of insulin for type I diabetics and insulin-dependent type II diabetics. It can also impact the amount of glucose that is stored as fat. When glucose accumulates in the bloodstream, the body uses insulin to attempt to remove it. If the muscle tissues, brain and organs do not use it up, the insulin will place it in storage. Lower glycemic index foods increase insulin sensitivity within the body. Overall, lower glycemic index foods have clear benefits for diabetics for numerous reasons.

The glycemic effect of foods is determined by a number of factors. For example, they type of starch (amylose vs. amylopectin), the physical entrapment of the starch molecules within the food, the fat and proten content of the food and the organic acids or salt that are present in the food. Some substances, such as vinegar, can lower the glycemic index of food. Fats or soluble dietary fiber can slow the gastric emptying rate which results in a lower glycemic index. Unrefined grains, which contain higher amounts of fiber, will lower the glycemic index of food. Refined (processed) flour has all of its fiber removed, which generates a very high glycemic index. Some bakers add additives (enzymes) to their unrefined grain breads to make the crust soft, which makes the starches in the bread more accessible, resulting in a very high glycemic index. Vigorous activity, or exercise, can cause a rapid drop in blood sugar levels, because the muscle tissues burn more glucose for energy. Selecting low glycemic index foods can extend the time that it takes for the glucose to be released into the bloodstream, which may prevent the sudden drops in blood sugar.

It is primarily carbohydrates and starches (another word for carbohydrates) that is converted into glucose. However, it should be noted that proteins, which contain no carbohydrates, are partially (up to 60%) converted into carbohydrates in the body.

Another index (insulin index) measures the typical insulin response to various foods. The insulin index is similar to the glycemic index, but rather that relying on the blood glucose level changes, the insulin index is based upon changes in blood insulin levels. For normal bodies (non-diabetic) this can be more useful than glycemic index. However, diabetics do not have normal blood insulin responses. Either the blood insulin level is determined by the amount of insulin injected (type I diabetic, or insulin-dependent diabetics). For these reasons it is best for diabetics to rely on the glycemic index, since it is based on values that remain consistent. They are independent of variables that occur during the process of managing diabetes.

Lean meats and proteins can cause an insulin response in a normal body, despite the fact that it has a glycemic index of zero, because a portion of them are converted into carbohydrates. They have a low glycemic index and a high insulin index in normal bodies. Dairy products, meat, fish, and eggs contain no carbohydrates (all are proteins) but will stimulate significant rises in blood insulin. This is the basis for low carbohydrate diets. The small amount of glucose generated by the converted carbohydrates, will cause the body to convert body fat back into glucose to supply muscle tissue.

So, how do they determine what the glycemic index of a food is? Typically, they have 50 volunteers, (healthy- non-diabetic) that have fasted for at least 12 hours, eat 50 grams of a single food item, for example: Brussels sprouts. Their blood sugars are taken before the test and periodically during the test. The changes in blood sugar levels will indicate how quickly the food item is broken down into glucose and absorbed. It will also indicate how quickly the blood sugar levels drop over a period of time. The values are plotted on a mathematical curve and compared to a standard, which happens to be sugar (glucose or white bread), which has an assigned value of 100. The area under the curve is calculated. The the resulting area is divided by the area for the control substance. That value is then multiplied by 100. The average value for all of the volunteers is the published value of the food items glycemic index.

Unfortunately, 50 grams is not necessarily the average serving size. So, a second value, which is intended to be more closely related to serving size was developed. Glycemic load will use the glycemic index to represent what a normal person would actually eat. The glycemic load is intended to give a more realistic value of the glucose reaction that can be expected from a serving of food. For example: if a food item has a glycemic index of 75 (as compared to pure glucose), and the serving size is 6 grams, the resulting value for the glycemic load (the glycemic index is expressed as a decimal = 0.75 x 6 = 4.5). That indicates that the food item is likely to spike the blood sugar levels about 3/4 of that found in pure sugar glucose.

Glycemic index and load values for many foods can be found on various internet sites. Some tables list food items for as many as 700 items. If a food item is not found on one of these tables, it is probably due to the fact that they have not been able to get volunteers to starve themselves, then eat 50 grams of an unpleasant food item (like chili powder). Different tables will give different values for the same food items. It is likely due to the fact that the averages for different test groups varied. The important thing is, that the values give a reasonable comparison (representation) of how foods will react in the body. It should also be noted that the volunteers in these tests were "normal". Diabetics typically will react to certain foods differently than a normal body would react. Consequently, each individual should experiment with the various low glycemic index foods to determine which ones their body reacts to. Then develop a list of foods that work best for their body.

It should also be noted that glycemic index and load are based on consuming one food item at a time. Meals rarely are comprised of only one food item. The recommended intake, in terms of glycemic load, is a total of 10 per day or less. When different foods are mixed, the conversion rate for the entire meal can be altered, which can result in an overall glycemic load for the meal that is lower than the total of the individual items. High fiber items, especially soluble-fiber, will significantly reduce the glycemic load of a meal. Fat and protein will also lower the overall glycemic load of a meal.

Fiber is the indigestible portions of food. It occurs most abundantly in legumes, vegetables, oat bran, nuts, seeds, phylum seed husks, fruits and grains. Soluble fiber comes from the storage materials of plants, which are used to store water in the plant. Soluble fiber dissolves and thickens in water, which forms a gel. It slows down the passage and absorption of food in the directional tract, resulting in an overall lower glycemic load. This is the basis of many carb-blocker products such as PGX, which is primarily glucomannan. Glucomannan is a very highly efficient water-soluble polysaccharide, which also forms a dense gel when combined with water.

The glycemic index, or load, of a meal can be determined by multiplying the percent of total carbohydrates of each of the foods by its glycemic index, then add up the results. The result is the glycemic index of the meal. The results may be skewed if the meal contains protein or fat. Despite the fact that up to 60% of proteins are converted into carbohydrates, less than 4% of the grams of meat and saturated fat results in glucose formation that is absorbed into the bloodstream. And, that takes up to four hours to occur. For that reason, most proteins are considered to have a glycemic index of zero. However, proteins added to carbohydrates do not slow the absorption of glucose despite the fact that they slow absorption. Proteins are therefore ignored in calculating the total glycemic index of a meal. Finally, determine the net carbohydrates from the meal. Since fiber is not digested, it does not become glucose and enter the bloodstream.

The net carbohydrates of a food item are determined by subtracting the net grams of fiber from the net grams of carbohydrates. For example: suppose that a serving of fruit has 16 grams of carbohydrates, and has 8 grams of fiber (16 - 8 = 8grams net). The serving of fruit has 8 grams of net carbohydrates.

It is also important to bear in mind that the accuracy of glycemic index and load are altered by a number of factors. The amount of cooking (heat levels and method of cooking) can substantially alter the glycemic rating of a food. Ripeness, particularly of fruit, can drastically alter the glycemic rating of food. Some foods will have a variation in glycemic index of as much as 30%. Bananas are particularly dependent upon ripeness in terms of glycemic index. The natural sugar levels, and in some cases, the levels of certain nutrients increase with ripeness. Rice is available in short grain, medium grain and long grain. The glycemic rating decreases significantly from short grain to long grain. For this reason, long grain rice is recommended over the other grains. The glycemic index of rice can vary from 38 to 94, depending upon whether it is short grain or long grain, and if it is white rice or brown rice. The difference is in whether the rice contains amylose or not, and how much it contains. The magnesium/calcium ratios of the different rice types will also vary significantly.

The point of all of this is, limiting the diet to low glycemic index foods can substantially improve the management of diabetes. However, the patient should consume a balanced diet that supplies and maintains as close to the 100% daily requirement of nutrients, vitamins and minerals as possible. Many research projects have shown that diets containing primarily low glycemic index foods have an overall lower a1c reading at the end of a 90 period. But, each individual must experiment with different low glycemic index foods to determine which foods their system is likely to respond to. The chemistry of individuals varies. Some individuals are unable to compensate for high sugar content in foods, because of chemical or nutritional shortcomings. Insulin/glucose metabolism is affected by a large number of factors including manganese, sodium, chromium, vanadium, biotin, potassium, vitamin C, vitamin B6, niacin/niacinamide, hormonal interactions, physical activity and the patient's weight. Magnesium, calcium, germanium, zinc, vitamin E, folate, PABA, and essential fatty acids also play important roles. An individual's propensity towards hypoglycemia and/or hyperglycemia will play a role as well.

Higher glycemic index foods (simple carbohydrates) require more resources of vitamins and minerals such as biotin, vitamin C, manganese and chromium. Manganese is typically unaffected by complex carbohydrate foods. Simple carbohydrates lower the manganese levels in hypoglycemic prone individuals, and increase the manganese levels in hyperglycemic prone individuals. Simple carbohydrates (including fruit sources of fructose) promote the formation of VLDL triglycerides, while complex carbohydrates do not. Therefore, the simple carbohydrates contribute to the risk of cardiovascular disease. Simple carbohydrates also decrease the omega-3 essential fatty acids and germanium levels, while complex carbohydrates support and enhance both. Complex carbohydrates are fiber- rich, while simple carbohydrates do not. Simple carbohydrates promote the formation of free radicals, which are responsible for oxidation (inflammation) and ultimately insulin resistance. Simple carbohydrates are linked to blood pressure level control within the body, both high and low levels.

The glycemic load should be maintained between 10 and 20 per day-the lower the better. There are a number of foods that are considered to have a zero glycemic index and load, besides proteins (also referred to as free foods). Broccoli, asparagus, Brussels sprouts, cauliflower, Kale, mustard greens, and others have a glycemic load of zero, because they typically do not cause glucose spikes. Legumes (beans) are very good sources of water-soluble fiber that also lowers the total glycemic index.

Glycemic load is a very powerful tool, that should become a standard in the planning of meals for every diabetic. Other very powerful diabetic tools can be found at the site listed below, including a free nutrition worksheet that allows the diabetic to track the daily consumption of over 30 vitamins minerals and nutrients. It lists the glycemic index and load for a large number of food items.