Published on January 24th, 2013 | by George Conte0
Glycemic index of foods
One can say that the main fuel of our human body is glucose. Glucose (sugar) circulates in our blood and our body tries to keep at the normal level of 90-100mg/dL or 5-5.5mmol / L.
When we eat carbohydrates our bodies breaks them down into glucose molecules and delivers them into our blood. After that these molecules reach our cells and our body uses them as fuel or stores them as glycogen or as fat when we have calorie redundancy.
If for example we eat carbohydrates then the sugar (glucose) in our blood rises and additional blood glucose is added. So if we were at 100mg/dL then glucose levels could rise (for a healthy body) up to 200mg/dL (hyperglycemia). Now to deal with this situation our body secretes insulin from pancreas. Insulin is simply a hormone that gives the signal “take glucose molecules from blood” to our cells. So as long as the cells pull glucose molecules from the blood, glucose levels fall and approach the normal level of 100mg/dL then insulin stops secreting from pancreas and thus cells stop pulling the glucose molecules from the blood and the level is stabilized again at close to 100mg / dL.
Carbohydrates are divided into simple (monosaccharides-disaccharides) and complex or polysaccharides (starchy, fibrous, etc.).
- Glucose is composed of one glucose molecule
- Fructose is composed of one molecule of fructose
- Lactose is composed of one molecule of Galactose
- Sucrose (the common sugar) is composed of one glucose molecule and one fructose molecule
- Maltose ) is composed of two glucose molecules
- Lactose (carbohydrate from milk) ) is composed of one Galactose molecule and one Glucose molecule
The polysaccharides (starch, fiber, etc.) are composed of many connected monosaccharide molecules.
Our body eventually breaks down all carbohydrates into glucose to use them as energy. In order to be absorbed and pass into the bloodstream carbohydrates must first be broken down by our digestive system into their simplest form “monosaccharides” and then are converted by the liver into glucose. More complex carbohydrates mean more smooth increases in blood glucose levels because our body will break down carbohydrates slower “bit by bit” into glucose molecules that will then pass into the bloodstream slowly and smoothly. In the other hand simple carbohydrates need less processing, resulting blood glucose levels to rise rapidly.
Diabetics need to control their blood sugar because they want the smallest possible fluctuation of glucose in their blood. This is why the Glycemic Index of Foods (Glycemic index- GI) was created. The glycemic index is a number that indicates the ability of a food, consisted of carbohydrates, to raise blood glucose in comparison to a reference food such as pure glucose or white bread.
In other words, researchers gave instructions to some people to eat a certain amount of glucose and for two hours they continuously measured glucose levels in their blood. Then they gave the same people the same grams of carbohydrates from different foods (eg bread, rice, potatoes, fruits, etc.) and again measured the concentrations of glucose in their blood. As expected, the pure glucose raised sugar levels in the blood more than all other foods and therefore was used as a reference carbohydrate. There is no need to analyze the formula from which this figure came after; all you have to know is that this figure reflects a growth rate of sugar caused by the food compared to the reference food. For example, when we say that a banana has “glycemic index of 60”, that means that the same grams of carbohydrate will cause 60% of the increase that pure glucose would cause. Low Glycemic Index is healthier because it means smaller and smoother increases of glucose in our blood.
Also the same food in different forms can have different Glycemic Indexes. For example apple juice has a higher GI than an apple in raw form because the digestive system will break down juice easier since it is already in “small pieces”).
How can the Glycemic Index help me?
Large increases of blood glucose involve large insulin secretions from the pancreas and high insulin concentrations in our blood favor lipogennesis (creation of fat tissue) because our body understands that there is caloric redundancy. This means that when fat cells find elevated insulin levels in the blood, they begin to synthesize fat from glucose and fat circulating in our blood. At lower concentrations of insulin we do not see the above phenomenon so intensely. So if you eat 2000 calories from pure glucose you will not have the same impact on your body in comparison to 2000 calories from bananas. In the case of pure glucose you will have a rapid increase in blood glucose from pure glucose consumed that will cause a large insulin secretion and more lipogennesis or fat stored.
When you are on a diet it is important to get your carbohydrate from low glycemic index foods such as oats, etc. because it will help you lose weight easier and faster. Even if you don’t need to lose weight you still should consume low glycemic index carbohydrates because it will lead to a healthier body protecting you from diseases like diabetes.
Food combinations that could lead to disasters!
For glucose to be stored as fat it must first be processed. For this conversion to happen a part of glucose is used as the energy source. Unfortunately, consumed fat doesn’t need any conversion and it is stored almost without any expenditure of energy.
Imagine what the example below can do to your body:
A meal combining high GI carbs like potatoes and fat like vegetable oil. Yes, I am talking about fried potatoes or French fries one of my favorite examples of junk food. Each time you eat French fries your fat cells start lipogennesis and have glucose (from potatoes) and fat (from vegetable oil) available and ready to store in huge amounts and fast! Indeed, a real and common disaster many people have no clue about.
If you think that the above example is a disaster think again. There is another phenomenon called “rebound hypoglycemia”. When you eat high GI foods, as we mentioned before blood glucose level rises rapidly but afterwards it falls below the normal 90-100mg/dL. This happens mainly with high GI foods because the fat cells continue to pull glucose molecules from the blood even when glucose levels fall into the normal range. This is because the insulin concentration remains high for some time even after it was excessively secreted. The result is a sense of drowsiness and after a while you are hungry again because your sugar levels drop. This is a vicious cycle and a nutritional nightmare because you gain fat rapidly while remain hungry. The result is to eat more and gain even more weight! Have you seen some extremely obese people that just can’t stop to eat all day for years? This is how they do it! They have found such food combinations.
What should I do now that I have learned about Glycemic index?
- The most important action you should take is to first think what are your favorite types of food that you love to eat.
- Secondly, you want to learn the GI of carbohydrates included in such types of food.
- After that just separate the low GI from high GI foods and try to avoid the ones with high GI and prefer to eat the ones with low GI.
It is as simple as that to be healthy and never have weight problems again that are caused by bad food combinations.
Glycemic index chart
In order to help you even more I will give you below the mean values of different glycemic index foods with pure glucose as a reference food: