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Quiz Your Glycemic Index Intellect (Pt. 2)

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April 9, 2010
	Dr. Gary Huber : Head Medical Ego

As we continue exploring our glycemic knowledge from yesterday, let’s move forward with our quiz by looking at some real-life food examples and see how well your glycemic smarts hold up.

1.  Which of these foods has the lowest and healthiest glycemic index?

            A.  White potato

            B.  Brown rice

            C.  Quaker Oats – slow cook, not instant

            D.  Rice cakes

White potato has glycemic index of 76, brown rice is 50, Quaker Oats is 67 and rice cakes is a whopping 82. 

Are you surprised by the Quaker Oats?  What if we looked at “instant” Quaker Oats? Making it “instant” is done by removing the fiber. Fiber is a good thing and slows down the digestion of these food in general.  Without good fiber content, food digests faster and causes a rapid rise in blood sugar. Not good. Instant oats has glycenic index of 75 compared to 67 for whole oats. 

How about a sweet potato or yam compared to a white potato? The yam or sweet potato has more fiber and will have a lower glycemic index around 50 to 60 compared to 76 or even as high as 85 for some types of white potatoes. Notice that there is not ONE number, there is a range depending on the type of item, whether it’s whole food or processed, and can even change depending on how it’s cooked.

2.  Which vegetables have the best glycemic index?

            A. Carrots, whole, raw

            B.  Carrots, cooked

            C.  Broccoli

            D.  Corn

Carrots are tricky. I have seen glycemic index ratings for raw carrots as low as 16, up to as high as 47. One reference had carrot juice rated at 43 and whole raw carrots at 47. How can that be true when we know whole carrots have their fiber in tact while this fiber is removed to make juice?  So no, it doesn’t always make sense and again, don’t get hung up on “exact” numbers, just follow the general principles as best you can. 

I have heard people proclaim that “carrots are high in sugar.” I think that is rubbish and these numbers show that to be true. Broccoli has a rating of 0, as do many of the cruciferous vegetables such as cabbage, cauliflower, and bok choy. So obviously our answer is C and these should be a high priority healthy food selection as often as possible. 

And what about good ol’ fashion sweet corn? We love it and the season is soon upon us . . . the index is 53. 

Not horrible but certainly much higher than most other vegetables.  So enjoy it on occasion but it should not be your daily “go to” veggie if you are trying to reduce sugar, insulin and body weight.

3.  Fruit versus fruit juice: how different is the glycemic index?

            A.  Grapefruit

            B.  Grapefruit juice

            C.  Orange

            D.  Orange juice

A fresh grapefruit rates a 25, very nice but converting it into juice it becomes a 48 and that’s “unsweetened.” How many of us actually buy unsweetened?  Oranges are 42 and orange juice goes up to 52. Not as big a jump but that’s unsweetened and often we buy reconstituted juice that has sugar or HFCS added.  The lesson here is that we should be eating WHOLE fruit and not fruit juice.

4.  Which of these foods has the lowest glycemic index?

            A.  Shredded wheat (Nabisco)

            B.  Wonder bread

            C.  Snickers Bar

            D.  Crunchy Nut Cornflake Bar (Kelloggs)

            E.  Cornmeal

In order of appearance they are:  83, 71, 68, 72, 69.  So yes, the surprise here is that the Snickers Bar is the lowest in this group. That’s because the Snickers bar contains peanuts, protein and fat. Anytime you combine protein and fat with any carbohydrate it will slow the rate of absorption and thus reduce the glycemic effect. The others in this list are all grains and grains tend to run high on any glycemic index. Does this mean that Snickers bars are healthy?  Probably not, but then how healthy are shredded wheat and cornflakes by comparison?

So, let’s wrap up our discussion with some take-home points I want you to glean from this…