Do you know the difference between the glycemic index and the glycemic load? Does it matter?
Both begin with "glycemic", which means that they both have to do with sugars and carbs. Not only how much sugar is in foods, but more importantly, how it affects your blood sugar levels.
In general, diets that are high on the glycemic index (GI) and high in glycemic load (GL), tend to increase the risk of diabetes and heart disease.
Starches, like those in potatoes, rice or wheat, are digested into simple sugar molecules, mostly glucose; this is because starch is simple a bunch of glucose units linked together in a complex manner. Digestive enzymes in the small intestine break those bonds so that the sugars become free and can be absorbed through the gut. Once in the bloodstream, then those sugars affect your body the same way that eating sugary foods like honey or candies do.
Glycemic Index (“how fast”)
The most common of the two terms is “glycemic index” (GI).
As the name suggests, it "indexes" (or compares) the effect that different foods have on your blood sugar level. Then each food is given a score from 0 (no effect on blood sugar) to 100 (big effect on blood sugar). Foods that cause a fast increase in blood sugar have a high GI. That is because the sugar in them is quickly processed by your digestive system and absorbed into your blood. They cause a “spike” in your blood sugar.
So, you can probably guess that pure glucose is given a GI rating of 100. On the other hand, chickpeas are right down there at a GI of 10.
Regarding GI: low is anything under 55; moderate is 55-69, and 70+ is considered a high GI food.
Remember, this is a measure of how fast a carbohydrate containing food is digested and raised your blood sugar. It's not a measure of the sugar content of the food.
How the carbohydrates in food affect your blood sugar level depend on other components of the food. Things like fiber and protein can slow the release of sugar into the bloodstream, and this can make even a high-sugar food, low on the GI scale.
So, lower GI foods are better at keeping your blood sugar levels stable because they don't increase your blood sugar level as fast.
Can you guess which food has a GI of higher than 100? Think of something super-starchy... For example, white potatoes have a GI of 111.
Glycemic Load (“how much”)
The glycemic load is different.
Glycemic load (GL) doesn’t take into account how quickly your blood sugar “spikes”, but it looks at how high that spike is. Basically, how much the food actually increases your blood sugar.
GL depends on two things. First, how much sugar is actually in the food. Second, how much of the food is typically eaten.
Low GL would be up to 10, moderate GL would be 11-19, and high GL would 20+.
GI vs. GL: which one to use?
So, let’s compare average (120 g) servings of bananas and oranges. A banana (GI=48) and an orange (GI=45) have almost the same glycemic index; this means they both raise your blood sugar in about the same amount of time. But, the average banana (GL=11) raises the blood sugar twice as high as the orange (GL=5) does. So, it contains more overall sugar than the same amount (120 g) of orange.
Of course, this is all relative. A GL of 11 is not high at all. So be assured that you can keep eating whole fruits!
In brief, the GI is the response to ingesting 50g of carbohydrate from a source, while the Gl is the GI weighted by the amount of food in one serving. In the table below are values for several sources of carbohydrates in the diet.
What does this all mean for your health?
Certain people should be aware of the effects that foods have on their blood sugar. People who have diabetes or pre-diabetes conditions like insulin resistance need to be aware of the glycemic index and glycemic load of foods they are eating regularly.
The GI and GL are just two factors to consider when it comes to blood sugar. Some high GI foods are pretty good for you but if you want to reduce the impact on your blood sugar, have them with a high-fiber or high-protein food.
If you have blood sugar imbalances or diabetes, you should probably be aware of the GI and GL of your food. If you are at risk of diabetes or heart disease, you might try swapping out some higher GI/GL foods and replacing with lower GI/GL foods.
Understanding the proper timing and portioning of each types of carbohydrates - vegetables, fruits, beans and legumes, grains and cereals - for your own body and how you are metabolizing these sources of carbs takes trial and error. Doing so under the guidance of an expert that can provide you with specific steps and an external point of view might be what you need! Connect with me if you want help!
References
http://www.health.harvard.edu/diseases-and-conditions/glycemic_index_and_glycemic_load_for_100_foods