What is the Glycemic Index?
The glycemic index (GI) is a ranking of carbohydrates on a scale from 0 to 100 according to the rate at which they raise blood sugar levels after eating.
High Glycemic Index Foods
Foods with a high GI (70+) are those which are rapidly digested and absorbed and result in marked fluctuations in blood sugar levels. [Medium GI foods rank 56-69 on the glycemic index.] Foods with high glycemic index values are useful for dietary variety and for replenishing muscle fuel stores after strenuous exercise. For people with diabetes who have low blood glucose levels - hypoglycemia - high glycemic index foods can quickly bring blood glucose levels back to normal.
Low Glycemic Index Foods
Low-GI foods (55 or less), by virtue of their slow digestion and absorption, produce gradual rises in blood sugar and insulin levels, and have proven benefits for health. Low GI diets have been shown to improve both glucose and lipid levels in people with diabetes (type 1 and type 2). They have benefits for weight control because they help control appetite and delay hunger. Low GI diets also reduce insulin levels and insulin resistance. Foods with low glycemic index values are useful to include in each meal to lower the overall GI-effect of the diet. Having an eating pattern that is lower in glycemic index is associated with better long term health.
Studies into Diet and Glycemic Index
Recent studies from Harvard School of Public Health indicate that the risks of diseases such as type 2 diabetes and coronary heart disease are strongly related to the GI of the overall diet. In 1999, the World Health Organization (WHO) and Food and Agriculture Organization (FAO) recommended that people in industrialized countries base their diets on low-GI foods in order to prevent the most common diseases of affluence, such as coronary heart disease, diabetes and obesity.
Low Glycemic Index Diet Plan
To have a low glycemic index diet, there is no need to eat only low glycemic index carbohydrate foods - simply substitute one high GI food that you would normally eat (eg. potatoes, white bread) with a low GI food (eg. pasta, whole grain bread) at each meal.
Effects of High GI Foods
Foods with a high GI score contain rapidly digested carbohydrate, which produces a large rapid rise and fall in the level of blood glucose. In contrast, foods with a low GI score contain slowly digested carbohydrate, which produces a gradual, relatively low rise in the level of blood glucose.
Glycemic Index Advice
Choose Low Glycemic Index Diets for Better Health and Weight Control
High glycemic index foods or high glycemic load meals typically provoke strong insulin responses, exposing the body to all the harmful effects of insulin, whereas low glycemic index foods or low glycemic load meals provide slower more sustained energy release, which helps maintain stable blood sugar and insulin levels. Low glycemic diets mitigate hunger, provoke reduced calorie intake and promote more efficient weight control.
Glycemic Index is not Perfect
Slavishly following a low glycemic index diet will not necessarily lead to optimum nutrition. Several low-GI foods are neither nutritious nor good for health. But a good understanding of glycemic index and glycemic load will help you make better food choices and assist in healthier meal-planning, as well as weight control.
How to Switch to a Lower Glycemic Index Diet
• Use breakfast cereals based on oats, barley and bran.
• Use dense, chewy breads made with whole seeds, not white bread.
• Eat less potatoes, but more al dente pasta.
• Choose basmati rather than white rice.
• Enjoy all types of vegetables.
• Eat plenty of salad vegetables with vinaigrette dressing.
• Balance a meal containing high glycemic index foods with extra low-GI foods.
• Adding food acids (like citrus fruits) helps slow stomach emptying and reduce glycemic response.
• Eat fewer sugary foods like cookies, cakes, candy, and soft-drinks
Blood Sugar Levels Help Control Hunger
One mechanism which controls hunger is the level of sugar/glucose in our blood. When our blood glucose level falls below normal, we feel hungry. Then, as we eat and as our food is digested, carbohydrate in the food is converted into glucose and enters our bloodstream. As our blood glucose levels rise, signals are sent to the pancreas which responds by secreting insulin. This insulin mops up the excess blood glucose and when once more our blood glucose levels fall below normal, the process is repeated.
Glycemic Index: List of GI Values of Common Foods- Not as comprehensive as Sleezys index
GI of Breakfast Cereals
Kellogg's All Bran 51
Kellogg's Bran Buds 45
Kellogg's Cornflakes 84
Kellogg's Rice Krispies 82
Kellogg's Special K 54
Shredded Wheat 67
Quaker Puffed Wheat 67
GI of Grains
Basmati Rice 58
Brown Rice 55
Long grain White Rice 56
Short grain White Rice 72
Uncle Ben's Converted 44
Noodles (instant) 46
Taco Shells 68
GI of Fruit
GI of Vegetables
Green Peas 48
Potato (baked) 93
Potato (mashed, instant) 86
Potato (new) 62
Potato (french fries) 75
Red Peppers 10
Sweet Potato 54
GI of Legumes/Beans
Baked Beans 48
Broad Beans 79
Cannelloni Beans 31
Garbanzo Beans (Chickpeas) 33
Lima Beans 32
Navy Beans 38
Pinto Beans 39
Red Kidney Beans 27
Soy Beans 18
White Beans 31
GI of Breads, Muffins & Cakes
Blueberry Muffin 59
Pita Bread 57
Pumpernickel Bread 51
Rye Bread 76
Sour Dough Bread 52
Sponge Cake 46
Stone Ground Whole wheat bread 53
White Bread 70
Whole Wheat Bread 69
GI of Pasta
Ravioli (meat) 39
Fettuccini (egg) 32
Spiral Pasta 43
Rice vermicelli 58
GI of Dairy Foods
Milk (whole) 22
Milk (skimmed) 32
Milk (chocolate flavored) 34
Ice Cream (whole) 61
Ice cream (low-fat) 50
Yogurt (low-fat) 33
GI of Snack Foods
Chocolate Bar 49
Corn Chips 72
Jelly Beans 80
Potato Chips 55
Snickers Bar 41
GI of Cookies & Crackers
Graham Crackers 74
Kavli Crisp bread 71
Melba Toast 70
Oatmeal Cookies 55
Rice Cakes 82
Rice Crackers 91
Ryvita Crisp bread 69
Soda Crackers 74
Shortbread Cookies 64
Stoned Wheat Thins 67
Water crackers 78
GI of Sugars
Glycemic Index of Foods (Carbohydrates)
Complex vs. Simple Carbs - The Old Glycemic Foods Classification
Carbohydrates used to be classified as simple carbs or complex carbs, depending on the number of simple sugars in the molecule. For example, carbs containing one or two simple sugars like fructose or sucrose were termed simple carbs, while starchy foods were categorized as complex carbs because starch is made up of long chains of the simple sugar, glucose.
Glycemic Index - The New Glycemic Foods Classification
Complex carbs were thought to trigger smaller increases in blood glucose than sugary foods. But the blood glucose (glycemic) response to complex carbs has been found by researchers to vary considerably.
Now, the basic indicator of the relative glycemic response to dietary carbs is the Glycemic Index (GI). For example, a baked potato has a glycemic index value of 85, while cooked brown rice has a glycemic index value of 55. According to the traditional system of classifying carbohydrates, both brown rice and the baked potato are complex carbohydrates despite the difference in their effects on blood glucose levels.
Response to High Glycemic Index and Low Glycemic Index Foods
The consumption of high-glycemic index foods results in higher and more rapid increases in blood glucose levels than the consumption of low-glycemic index foods. Rapid increases in blood glucose trigger larger insulin secretions from the beta-cells of the pancreas. Unfortunately, the high insulin levels triggered by high-glycemic index foods typically (within hours) cause a sharp decrease in blood glucose levels (hypoglycemia). By comparison, low-glycemic index foods result in more gradual, sustained increases in blood glucose and consequent lower insulin secretions from the pancreas.
I'm glad you posted that, Dr X. A lot of people, I think are still confused
by that compex vs. simple carb thing.
Manufacturers still try to fool us with it, too. Look at the descriptions of
maltodextrin products. It's a "complex carb". They conveniently don't
mention the high GI rating.
I have to agree with eric thats a really good post I was one of the people who was still somewhat confused.
Deserves a sticky...
I came across this site that has a lot of explanation about all aspects of carbs and also about glycemic index and glycemic load and the difference between them.
What is Glycemic Load?
"Glycemic Index" Based on 50 Grams of Useable Carbs
Glycemic Load is the application of the glycemic index to a standard serving of food. Remember, the glycemic index (GI) of a food is not based on commonly consumed portion-sizes of foods. Instead, GI is measured by giving volunteers a portion size sufficient to contain 50g of useable carbs. Therefore the portion size of each GI-tested food will vary according to how much carbohydrate it contains. For example, carrots contain only about 7 percent carbs, so the test-portion of carrots eaten by the test-volunteer will be huge - about 1.5 pounds. Serving sizes of foods (like bread) which contain a higher percentage of carbs, will be smaller.
The Drawback of the Glycemic Index
As explained above, glycemic index tests are not performed on typical portion sizes. So, by using the Glycemic Index alone, the glycemic effects of foods containing a small percentage of carbs are likely to be overstated, while the glycemic effects of foods containing a high percentage of carbs are likely to be understated. For example, foods that are mostly water or air will not cause a surge in your blood sugar levels even if their glycemic index is high.
This is why scientists developed the idea of Glycemic Load. It ranks foods according to actual carb content (eg. in a typical portion-size), not how fast a 50g amount of carbs raises blood sugar levels.
Glycemic Load - How is it Measured
Glycemic load tells you how much carbohydrate is in a standard serving size of food. To calculate glycemic load in a typical serving of food, divide the GI of that food by 100 and multiply this by the useable carbohydrate content (in grams) in the serving size. For example, the glycemic index of carrots is about 47. Carrots contain about 7 grams of carbohydrate per 100g of carrots. So, to calculate the glycemic load for a standard 50g serving of carrots, divide 47 by 100 (0.47) and multiply by 3.5. The glycemic load (GL) of carrots is therefore 1.6.
Glycemic Load More Accurate Than Carb Content
Although a low-carb food typically has a lower-GI value than a high carbohydrate food, choosing foods purely on the basis of the amount of carbohydrates they contain is less beneficial for blood glucose control and general health than relying on their glycemic load (GL). Don't forget, the glycemic load of a food is its GI value per serving, and the GI value of a food is the definitive guide to its effect on glucose metabolism and thus blood sugar levels. Bottom line: choose what carbs to eat on the basis of their GL, not simply their carbohydrate content. In fact, low GI diets have now superceded low carb diets, as the latter are regarded by most dietitians as less healthy and less easy to comply with than GI weight loss plans.
Article from here
What about Portion Size? And how is GI Determined?
The glycemic index is about the quality of the carbohydrates, not the quantity. Obviously, quantity matters too—and that is the reason for the glycemic load values—but the measurement of the glycemic index of a food is not related to portion size. It remains the same whether you eat 10 grams of it or 1000 grams. That's because to make a fair comparison tests of the glycemic indexes of food usually use 50 grams of available carbohydrate in each food. You can eat twice as many carbohydrates in a food that, for example, has a glycemic index of 50 than one that has a glycemic index of 100 and have the same blood glucose response.
Basically, test foods are fed to various people, some with diabetes, others without, in portions that contain 50 grams of available carbohydrates. The 50 gram carbohydrate portion is specified in Dr. Wolever's methodology paper (see bibliography below) as 50 grams of available carbohydrates. "That means it excludes the fiber," Professor Brand-Miller writes me. "We have always used a 50 gram available carbohydrate portion and often relied on manufacturers to give us the composition data. I am aware of only one instance where we been given incorrect information and therefore inadvertently included the fiber in the 50 gram carbohydrate portion…but there may be some papers from developing countries where the data is not reliable."
For example, to test boiled spaghetti, the scientists give their subjects 200 grams of spaghetti, which according to standard food composition tables provide 50 grams of available carbohydrate. The scientists compare this response with the volunteer's response to a reference food, which may be either glucose or white bread. Both for the test and for the reference foods the volunteer's response over the next two or three hours is calculated. Rather than measuring a single point, they make the more precise measurement of the area under the curve. Then, they repeat the whole process on different days to reduce the effect of day-to-day variations.
Next, the area under the response curve for the test food is expressed as a percent of the mean value for the reference food for the same subject. Finally, these percentages from each subject are averaged together to obtain the GI for that food. For more information, see Wolever, Thomas M.S. et al. "The Glycemic Index: Methodology and Clinical Implications," listed in the bibliography below.
MUST READ interview with Emma Leigh by Jamie Hale:
Jamie Hale interview with Emma Leigh
Glad you enjoyed the interview and I do hope it helped shed more light on some of the issues around the use of the GI.
great to see you here :)
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