The Glycemic Index, developed in early 1980s by Dr. David Jenkins, a Nutritional Sciences Professor at University of Toronto, ranks carbohydrate-rich foods by how much they raise blood glucose levels compared to glucose or white bread. Carbohydrates include such foods as bread, rice, pasta, flour, sugars, fruits and vegetables.
When you eat food that contains carbohydrates, the sugar (glucose) from the food breaks down during digestion and gives you energy. After you eat, your blood glucose level rises; the speed at which the food is able to increase your blood glucose level is called the “glycemic response.” . Foods that raise your blood glucose level quickly have a higher GI rating than foods that raise your blood glucose level more slowly
It was originally thought that all carbohydrates would raise blood sugars at the same rate. However, through Dr. Jenkins research it was shown that all carbohydrates are NOT created equal. Glucose was given the rating of 100 while simple sugars, like table sugar (sucrose) had a glycemic index of only 61 and fructose had a glycemic index of only 19.
Low-glycemic foods are whole grains, fresh fruit and vegetables and legumes.
The glycemic index measures the blood sugar response of different carbohydrate foods compared to a standard reference food, typically glucose. In Glycemic Index research, subjects are given 50g of carbohydrates in the form of glucose or white bread. The corresponding rise in blood sugar levels is measured and given a number of 100. When subjects are given others foods to consume, the blood sugar response of these foods are measured, compared to the “standard”, and assigned a number.
The glycemic load looks at the blood sugar response when a particular food is consumed at its average serving size. Some fruits and vegetables have moderate to high glycemic ratings (i.e. carrots) but you would need to consume a very large amount of these foods to make the food high-glycemic.
Example: Raw, medium size carrot has only 6g of carbohydrates so you would need a large quantity to get a high glycemic response.
Low-glycemic foods are slowly digested and absorbed, which causes gentle rises in blood sugar and insulin levels. Lowering your insulin levels is not only a key factor in weight loss, but also the secret to long-term health.
Choosing low-glycemic foods will help you to:
First, you must understand the three classes of macronutrients: carbohydrates, proteins and fats. Proteins and fats contain no carbohydrate, or so little that their GI cannot be tested. Remember, the GI is a measure of carbohydrate quality. Proteins and fats, eaten alone, won't have much effect on your blood glucose levels. Adding lean sources of proteins, including legumes as well healthy fats and will lower the glycemic index of carbohydrates so each meal and snack should include these components.
Today we are in the midst of the greatest health care crisis to hit the modern western world—obesity. What is even more concerning is the fact that it is now projected that over 30% of the next generation will develop diabetes sometime in their life. The most important aspect of our health is determined by the foods we choose to eat.
Studies have revealed that 85 to 90% of the carbohydrates that adults and children are eating today in the U.S. and Canada are highly processed and high-glycemic. This has led us to repeatedly spike our blood sugar and eventually become much less sensitive to our own insulin. The insulin resistance that has developed because of our poor diet and lack of physical activity is the primary reason we are in the midst of not only an obesity epidemic, it is the major reason so many of us are becoming diabetic.
It has now been shown that nearly 25% of the adult population has full-blown insulin resistance and another 25% are well on their way to developing it. This leads to a constellation of health problems that has been defined by the medical community as the “metabolic syndrome". When this occurs, you not only begin aging much faster than you should, but you also gain an unusual amount of weight around your middle that you can’t lose. You begin to hold on to fat like a sponge holds on to water. This is all the result of an underlying resistance to your own insulin.
Alcoholic beverages contain very little carbohydrates. In fact, most wines and spirits contain virtually none, although beer contains some (3 or 4 grams per 100 mL). A beer (10 ounces) contains about 10 grams of carbohydrate compared with 36 grams in the same volume of soft drink. Wine, especially red wine, has the extra benefit of antioxidants that, in animal studies, help prevent insulin resistance. Remember, moderation is key.
The reason classic pasta is GI friendly is that it is made from semolina wheat flour that has been more coarsely ground than the flour used to make breads, etc. Secondly, the starch in cooked pasta is less “gelatinized” than the starch in bread, making it slower to digest and absorb. Choose a whole grain pasta when possible.
Note: The longer the pasta is cooked, the more gelantinized the starch becomes and the higher the GI. Pasta should be cooked al dente ('firm to the bite') because overcooking boosts the GI. Although most manufacturers specify a cooking time on the packet, don't take their word for it. Start testing about 2-3 minutes before the indicated cooking time is up.
Some types of bread and potatoes have a lower GI than others. Sprouted grain breads, sour dough, course barley bread, and whole-grain pumpernickel are better choices than white and whole wheat. Russet potatoes, baked and mashed potatoes have a high GI while sweet potatoes, yams and new potatoes have a low to moderate glycemic rating.
True sprouted grain breads are made by first sprouting the wheat kernels. When grains begin to sprout, carbohydrates stored in the grain are used as the fuel source for the new shoots. They are then mashed to form the dough. This method retains all the bran, germ and endosperm, giving you up to three times more fibre.
The low-carbohydrate craze is on the downswing! The problems with many low-carbohydrate diets are that they have been shown to be less effective, less healthy and at times dangerous.
Low-carbohydrate diets are unnecessarily restrictive. They tell people not to eat things like, bread, potato, rice, grains and many fruit and vegetables. This may spell trouble in the long term if saturated fat takes the place of carbohydrates. Low-GI diets strike a happy medium between low-fat and low-carbohydrate diets - you can still have carbohydrates, but must choose them carefully.
The benefits of choosing low-glycemic foods go beyond weight management. They include reduced mood swings, less fatigue, mental alertness, sustained energy and reduced inflammation.
The GI can be a useful tool in helping athletes select the right type of carbohydrate to consume both before, during and after exercise. Studies have consistently reported that a low-glycemic, pre-exercise meal results in better performance due to stabilized blood sugars and possibly improve endurance performance.
Eating high-GI meals before exercise may result in an athlete fatiguing within the first 30 minutes of the exercise period. An endurance athlete such as a marathon runner would want to consume moderate to high glycemic foods during events that last over 1 hour.
If you are exercising for weight loss purposes or are involved in weight restricted sports, low-GI carbohydrates after exercise are more beneficial because the lower glucose and insulin concentrations in them will not store fat.