Glycemic Index and Glycemic Load: A Way to Stop Hunger, Fatigue and Control Weight.
Do you get cravings for sweets? Do you find yourself not able to stop eating? Do you crash mind day? All these could be traced to the types of foods you are eating.
When you eat foods or drink beverages with carbohydrates, they affect your blood glucose levels. Not all carbohydrates are created equal. Some carbohydrates will produce large increases in blood sugar, while some have a smaller effect.
When your blood glucose levels are high, your body responds by producing insulin. Insulin is a hormone made in the pancreas that is secreted to clear high blood glucose levels.
The glycemic index assigns a value to carbohydrates from 0 to 100 to describe the extent it will raise your blood sugar levels.
Now let’s assign some foods to these ratings.
Let’s say you start your day with a high glycemic food only like a donut or some toast. Your blood sugar levels increase beyond what your body wants, often called a sugar spike. Then your brain will send a message to your pancreas to secrete insulin to lower the high glucose level in your blood.
This insulin response will mirror the glucose response, so it’s going send quite a bit of insulin to clear the glucose. The result is your blood sugar levels will now fall below normal, often called a sugar crash. This is when you start to have craving and begin to feel tired, moody and maybe depressed.
You satisfy your craving with something sugary and the cycle start all over again. You are now on the sugar roller roster. Here is what it look like graphically and it does in fact look like a roller roaster.
There are a number of factors that affect glycemic index.
The Type of Starch
Starches are your complex carbohydrates. Specific carbohydrate classification is discussed in the article, “Carbohydrates-What, Why and How: One of the Essential Nutrients for Good Health (#2 in series)."
Most starches are amylose or amylopectin. All that means is that some absorb water easily and reach your blood stream quicker. These are your amylopectin starches and are found in russet potato (GI 85), and rice (GI 95). Other starches are closely packed and do not absorb water well. These are your amylose starches and are found in kidney beans (GI 28) and long grain rice (GI 50). Amylose starches will not breakdown a quickly and spike your blood glucose levels, while amylopectin starches will (1).
The Bran Coating
Bran acts as a physical barrier that slows down the digestion of starch. Sometimes in whole grain bread (not to be confused with whole wheat bread) you will see little specs. That is the bran.
All bran and pumpernickel bread have a low GI, 38 and 50, respectively. While a bagel and corn flakes have high a have a high GI, 72 and 92, respectively. This is because the bran shell is removed in the latter.
Viscosity of Fiber
Viscous, soluble fibers transform intestinal contents into gel-like substances. This tends to slow the movement of food though digestion and hence slows glucose from entering your blood too fast. It would also make you feel fuller longer.
If you compared eating Cheerios (GI 78) to rolled oats (GI 51), you would fell fuller longer eating the rolled oats opposed to the Cheerios. This is because the roll oats contain soluble fiber.
Sugar Type
There are four main sugars: sucrose, maltose, fructose and glucose. Sucrose is made up of two sugars, glucose and fructose. Maltose is made up of 2 glucose molecules. All of these are eventually broken down into glucose. Glucose is your body’s preferred energy source.
Glucose and maltose have the highest GI at 100 and 105, respectively. Sucrose still scores high at 60, but fructose has only 19. This is because fructose has to pass though the liver before being broken down to glucose. Spoke about further in “Carbohydrates-What, Why and How: One of the Essential Nutrients for Good Health (#2 in series)."
Fat & Protein Content
Fat and protein slow down gastric emptying, and thus, slows down the digestion of starch. If you ate a complex carbohydrate with protein or fat it would slow down the breakdown of glucose entering your blood. This would lead to less insulin being secreted.
The graph below shows what happens to blood sugar levels when you eat different foods. Notice the green line, which represents eating protein, fiber and complex carbohydrates together. You do not see a spike in blood glucose levels and you see stable levels for a longer period of time (3 hours).
Cinnamon has gain attention for aiding in obesity, glucose intolerance, diabetes mellitus and dyslipidaemia (high cholesterol). There have been extensive studies conducted concerning the effects of cinnamon on blood sugar levels. The Nutritional Journal performed an analysis of these studies. It concludes both true cinnamon and cassia cinnamon has the potential to lower blood glucose in animal models and humans, but more studies are needed (2).
Acid Content
Acid slows down gastric emptying, and thus, slows down the digestion of starch. Sourdough wheat bread has a GI of 54, lower than Wonder bread (GI 73), because of the acid in sourdough. Similarly, if you added vinegar to a complex carbohydrate it would slow down the digestive process.
Food Processing
Highly processed foods require less digestive processing. The more your food is processes the faster it is absorbed into the blood stream. As food is processed two things happen. The food is ground finer and finer and the particles become more uniform in size. The result is similar digestion times for the bulk of food ingested. Second, the surface area of the food becomes much larger and thus the food digests more quickly because the enzyme can attack the food more quickly. That is why eating the old fashion, rolled oats (GI 51) is a better choice than the processed Quick, 1-minute oats (GI 66).
Cooking
Cooking swells starch molecules and softens foods. Once swelled, the enzymes that break down food in the stomach are able to access the starches and convert them to sugar more quickly. This means if you over cook your carbohydrate the GI will increase. Al dente spaghetti – boiled 10 to 15 minutes has a GI of 44, but if you overcook it to 20 minutes the GI goes up to 64.
Similarly, ripeness of fruit will affect GI-the riper a fruit the higher the GI. This is even true for potatoes. Small, new season potatoes tend to have a lower GI than fully grown spuds left in the ground longer. Letting your potatoes get cold will lower their GI too. This is due to the resistant starch factor (3).
It is vital to understand that you should not just look at the glycemic index when evaluating carbohydrates. Instead you need to look at the glycemic load (GL). Glycemic load measures the degree of glycemic response and insulin demand produced by a specific amount of a specific food. It reflects both the quality and the quantity of dietary carbohydrates. It provides a much accurate picture of your glucose response.
GL = GI/100 x CHO (grams) per serving
Example: GL of an apple = 40/100 x 15g = 6g
There are apps that will do the calculation for you. Here are some free ones.
Just like glycemic index, glycemic load have ratings.
The differences between glycemic index and glycemic load are quality and quantity. Glycemic index ranks carbohydrates based on their immediate blood glucose response. GI represents glycemic quality. It does not consider quantity.
Glycemic load helps predict blood glucose response to specific amount of specific carbohydrate food. Glycemic load takes into account both quality and quantity.
Everyone could benefit by adding some low glycemic foods to their diet. There are documented benefits to lowering the GI of your diet. You will have more stable blood glucose levels that help feelings of hunger, tiredness and fatigue. You will decrease your risk of type 2 diabetes and heart disease. You will lower you cholesterol. And low glycemic foods promote weight loss.
However, experts agree that you should not focus exclusively on achieving a low glycemic load diet with all low glycemic index food choices.
This may lead to a diet that is high in fat and calories and low in fiber and carbohydrates. Instead, aim for a well-balanced diet that includes low glycemic index carbohydrates. Use glycemic load as a guide for controlling portions.
Low GI carbohydrates allow for larger portions, while regulating the GL -so you will be able to eat more and keep you blood sugar in check. High GI carbohydrates require smaller portions to regulate the GL, so you will need to eat less to keep you blood sugar in stable.
At breakfast you can choose a high fiber cereal like oats, barley or bran. If you can’t give up high glycemic cereal, add berries, nuts, or flaxseed to it. Do not forget calories do count and nuts are calorically dense.
Choose dense, whole grain and sourdough breads and crackers. Or add a healthy protein to high GI breads and crackers.
An excellent and probably the easiest way to approach this is to include more fruits and vegetables to your diet. If you are not eating at least 2-5 fruit and vegetables a day, you should start. The benefits go beyond stable glucose levels into disease and malnutrition prevention.
The article "Healthy Eating Guidelines: Tips From Around the World" can help you make better food choices.
Remember a balance diet is key and the glycemic index is a guide not a bible.
Next week starts a series on resistance training.
Learn about the principles of training and how to correctly order yours exercises.
Have a Fit Day!
