In this video we discuss what is the Glycemic Index and Glycemic Load, and what is the glycemic index. We also cover how the glycemic load affects blood sugar levels and things that affect the glycemic index and glycemic load.


Transcript (partial)

So, what is the glycemic index. It is a way to analyze carbohydrate foods based on their impact on blood sugar LEVELS. The GI ranks carbohydrates on a scale of 0 to 100 based on how much they raise blood sugar levels after eating. Foods with a high GI are rapidly digested and absorbed and therefore cause large fluctuations in blood sugar levels. Lower GI foods are more slowly digested and produce gradual rises in blood sugar levels.

How is a food’s GI VALUE determined? After an overnight fast, a group of 10 people are given a serving of a food item. This serving contains 50 grams of available carbohydrates. Available carbohydrates does not include the fiber content. After the food has been consumed, blood sugar levels are measured every 15 to 30 minutes, over a two hour period.

These results are plotted on a graph. Next, the people are given 50 grams of carbohydrates of a reference food, either white bread or pure glucose. The same process is followed, and these results are plotted. The area under the curve for the reference food is given a value of 100. the area under the curve of the test food is then calculated as a percentage of the reference food area. What ever that percentage is is its GI value. This is how the GI rates foods.

Most organizations use a high, medium, and low rating scale. Carbs with a GI value of (55 or less) are rated as low, A Medium value lies between 56 and 69, and a high value is 70 or more.

Glycemic load is another way to analyze carbohydrate foods. It takes into account portion sizes. While the GI looks at only 50g carb amounts, Gl looks at the available carbs in a portion size. The GL equation is as follows. The scale for Gl is as follows, High = 20 or more, medium = 11 to 19, and low is 10 and under. Lets look at a couple of examples.

Here we have a serving size of 1 cup of diced pineapple, which contains 19.5 grams of carbs and 2 grams of fiber, giving it 17.5 grams of available carbs. And here we have a serving size of 1 cup of watermelon which contains about 11.5 grams of carbs, and 0.6 grams of fiber, so it has roughly 11 total grams of available carbs.

Next we have a serving size of 2 slices of white bread, whch contains about 24 total grams of available carbs. The Gi value of pineapple is 66, watermelon is 72, which puts it in the high Gi category, and white bread has a Gi of 70. I am going to put the Gl calculations on the screen for you. And, we see that the gl for the serving of pineapple is 11.55, watermelon is 7.92, and white bread is 16.80.

Lets take a look at ice cream. It has a Gi of 36, really good, a serving size of 1 cup yields a GL of about 11.52. So, a low GI and a medium GL, not too bad. But, why are these numbers low, well, when we look at the total profile of ice cream, we see it has 14g of fat (8g sat fat) in that serving. So, as the body digests it, the glucose release will be slower because the body has to break down the fat in addition to the carb. This gives it a lower GI.

Other things that effect a foods Gi value is how it is cooked, any cooking will raise a foods value, however, slow cooking will not raise GI’s value nearly as much as fast cooking such as microwaving. The more a food has been processed the higher the GI value will be, and what other types of foods it is being consumed with will affect its value as well.

The GI and GL can be useful in relation to blood sugar level spikes. However, because the food has a low GI or GL value, This does not mean the food is healthy or unhealthy. The GI and GL can be a helpful tool in evaluating food, however, it is only one tool. Look at the fat content, the fiber content, look at how much processing the food has gone through, and how the food was cooked.

One last thing, many studies have shown that consumption of lower glycemic foods has delayed the return of hunger and decreased subsequent food intake. As we always say here, try and increase your whole food consumption, try and minimize the processed foods, but, don’t be afraid to eat the foods you love, just do it in moderation.

Timestamps
0:00 Intro
0:16 What is the glycemic index?
0:46 How is the glycemic index for foods determined?
1:40 Glycemic index rating scale
1:55 What is the glycemic load?
2:22 Glycemic Load rating scale
2:34 Food examples
4:01 Drawbacks of glycemic index and load
4:44 Other things to consider


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