We hear the word “blood sugar” very often and most of us know it is associated with eating sugary foods. Yes it is true, but this is not the whole story. My purpose with this post is to reveal what blood sugar really is, the effect of carbohydrates, proteins and fats on blood sugar, glycemic index and glycemic load.
Carbohydrates are the main energy source in our body and they are found in grains, vegetables, fruits and dairy products. Whatever goes into our body with any form of carbohydrate, the body needs to break it down into the simplest form to metabolize completely.
The term blood sugar indicates the amount of glucose (simplest form of carbohydrates) circuits in our blood stream. It can be tested either fasting state and -ideally- 2 hours after eating a meal. Generally, fasting blood sugar test is used as a first step of the diabetes diagnosis. In a healthy population, fasting blood glucose levels fluctuates between 3.3-5.8 mmol/L and it is expected to be <6.5 mmol/L on the fasted state- 2-hours after a meal. (1)
Beside the carbohydrates, proteins also have an influence on the blood sugar, however not as much as carbohydrates (That is the reason why proteins have to be limited on ketogenic diet). In addition to that, not every carbohydrate containing food has the same effect on blood sugar. To make this clearer, Dr. David Jenkins from University of Toronto came up with “glycemic index” (GI) concept for the people with diabetes. His aim was to classify carbohydrate containing foods depending on how quick or slow and how high they increase the blood sugar. Basically, those numbers are ranked as a result of the blood sugar change after absorbing 50 grams of glucose. Glucose and water mix used as a reference with GI rate 100. (2)
Low glycemic index foods has GI between 0-55
Medium glycemic index foods has GI between 56-69
High glycemic index foods has GI > 70
Low GI foods are digested and absorbed slowly. Eventually, their impact on blood sugar change is much smaller and slower than medium and high GI foods.
GI of foods and meals is influenced by several factors;
Even GI is a useful tool to find out how our blood sugar is affected from what we eat, it misses out the idea of portioning the food and makes it challenging to apply in daily life.
To find a more useful way, the concept of glycemic load (GL) is developed. GL takes the glycemic index and the quantity (grams) consumed into consideration (4). That means, consuming a great amount of low GI food may have high GL. In the same way, consuming limited quantity of high GI food may have low GL.
Similar to the glycemic index, consuming high glycemic load shows rapid increase and fall on the blood sugar levels.
Low glycemic load foods has GL <10
Medium glycemic load foods has GL between 11-19
High glycemic load foods has GL > 20
( Resource: University of Sydney DataBase)
Other Health Benefits of Low-GI & Low-GL Diets
Following a low glycemic index and glycemic load diet has been clinically proven to reduce blood sugar levels of people with type 2 diabetes. (6)
Low GI foods mostly consist of foods with high fiber content. Therefore, low GL diets protect heart health by reducing LDL cholesterol (bad cholesterol). (7) In consequence of high fiber content of low GI foods, it helps you to feel full for a longer period of time. Additionally, it regulates your blood sugar by preventing extreme blood sugar fluctuations which may cause those midnight cravings, binge eating etc.
Some studies have shown protective effects of low GI & GL diets from certain cancer types (colorectal, breast and endometrial). (8) (9)
Those health promoting characteristics listed above are reasonable facts to place emphasis on low glycemic load. It reminds us to nourish our body with a variety of less processed and whole food products by considering the amount consumed.
1. Diabetes Canada, 2018. Retrieved from; http://guidelines.diabetes.ca/cpg