Most who have started to eat Paleo, Primal, Zone, Atkins or any other low/no carb style of eating are probably familiar with the term Glycemic Index. I'm sure even folks not doing these plans have at least heard the term at one point or another. I'd like to cover what the Glycemic Index is, its limitations, and a much better way to gauge the relative amount of glucose in foods: Glycemic Load.
The Glycemic Index (GI) measures how quickly blood sugar levels rise after eating a particular food comparing it with eating pure glucose, which ranks 100 on the scale. The more quickly blood sugar rises, the more drastic is the insulin response need, which is vitally important info for diabetics. Its a measure of the quality of the carbohydrate in a given food. Foods are tested and compared based on 50g of available carbs (i.e. no fiber) of that food. Foods that score 55 or less are considered low GI foods and scores of 70 and above are considered high and to be avoided.
Simple, right? Just eat foods with low GI values and avoid the high GI. Not so, it turns out. While it may be a good starting point when deciding what kind of carb-containing food to eat, its far from perfect for a few very important reasons. This is what makes Glycemic Load a much better guide. So what's wrong with the Glycemic Index?
Lots, actually. For one, you will notice that earlier I mentioned it's based on 50 grams of carbs of that food. That's great for a test, but that doesn't take into account the amount in how much we actually eat in a normal portion! Lets use beets and whole wheat pasta as an example. Beets have a relatively high GI of 64, but how many beets would one have to consume to get to 50g of digestible carbs? about 5 cups. Unless you are a serious beet addict, I doubt anyone is going to eat that much in a serving. Whole wheat pasta has a GI of 37. Pretty low. However it only takes 1 cup of pasta and 1/2 cup of spaghetti sauce to get to that 50g. That's not a a big portion. In the end, the beets would have less of any effect than the pasta, despite the higher GI number.
Other factors GI doesn't account for are cooking method, ripeness, amount of fiber or water in that food. Cooking can raise sugar content in fruits and vegetables and the more ripe they are, the more sugar they contain. Foods that have lots of water are going be less dense in the sugar per serving, such as watermelon. Watermelon has a high GI (72), but has only 9g of sugar in an actual serving (1 cup, diced) due to the fact they are mostly water.
Here is where Glycemic Load (GL) comes to the rescue. It is much more accurate since it not only takes the GI information (quality), but also the normal serving size (quantity). There are GL charts online but its easy to to figure out by just multiplying the Glycemic Index of the food by the amount of carbs in a serving (excluding fiber) then divide by 100. The formula is below...
GL = amont of carbs in serving (minus fiber) x Gi /100
Foods with a low GL would be in the 0-10 range and high would be over 20, with 11-19 being moderate. Let's compare the glycemic load for beets and whole wheat pasta and sauce example earlier.
For the beets, we would multiply the GI of 64 by 7grams of carbs (1 cup serving) equals 448. Dividing by 100 gives us 4.48, a very low GL number. The pasta is GI of 37 x 37grams of carbs (1 cup) and dividing by 100 equals 13.7. Tomato sauce would be GI of 64 x 20g of carbs (1/2 cup) and divide by 100 yields 12.8 Add them up and the GL total is around 26.5 which is considered high.
Lastly, here is a chart to use to look up the GI and GL of foods for reference. If you cant find it on there, it should be easily findable with a search engine.
Hope this helped and feel free to contact me with any questions!
No comments:
Post a Comment