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Whole fruit vs juice in Glycemic index

Answered on August 19, 2014
Created April 16, 2012 at 2:01 PM

Fruit juice has is higher than whole fruit on the index. Why? Is it because your body does not have to extract the sugars from the fiber? Or could it be because the fiber feeds your gut flora? Or maybe there is another reason that I missed.

510bdda8988ed0d4b0ec0b738b4edb73

(20888)

on April 18, 2012
at 03:16 AM

From here: http://www.fao.org/docrep/W8079E/w8079e0a.htm "The glycemic index is defined as the incremental area under the blood glucose response curve of a 50g carbohydrate portion of a test food expressed as a percent of the response to the same amount of carbohydrate from a standard food taken by the same subject. The italicized terms are discussed below because the methods used to determine the glycemic index of foods and to apply the information to diets may profoundly affect the results obtained." But if you don't believe me, google "Glycemic Index Definition" and you'll see

Medium avatar

(10611)

on April 17, 2012
at 09:52 PM

@miked University of Sydney tests GI, Wiki doesn't. Follow the link and read the explanation of the methodology for testing GI, and look at how specific foods were tested. The portions/carb contents vary greatly from food to food. Foods with high carbohydrate content per portion - like rice - have high GI, while foods with low carbohydrate content - like yoghurt - have low GI. You can call it glycemic load if you like but Sydney calls it GI.

E5c7f14800c5992831f5c70fa746dc5c

(12857)

on April 17, 2012
at 03:53 PM

According to this http://lowcarbdiets.about.com/od/whattoeat/a/glycemicindlist_3.htm Fruit juice isn't higher GI than whole fruit, at least when you compare oranges/pineapples.

E5c7f14800c5992831f5c70fa746dc5c

(12857)

on April 17, 2012
at 03:51 PM

Glycemic index isn't based on how fast you can eat something though, so I don't really get your point?

E5c7f14800c5992831f5c70fa746dc5c

(12857)

on April 17, 2012
at 03:50 PM

I can eat 4 oranges as fast as I can drink 4 oranges worth of juice. It's extremely easy to eat oranges very fast if you juice them in your mouth :) If you calculate juicing into the time it takes to eat, just eating them is faster.

510bdda8988ed0d4b0ec0b738b4edb73

(20888)

on April 17, 2012
at 03:08 PM

That would be implicitly taken into account because the glycemic index measure blood glucose, so if it never gets to the blood, it's not there to be measured. However, I don't think our guts (compared to other primates) do much in fermenting sugars for fuel. It's very minor compared to everything else.

A3bb2c70384b0664a933b45739bac32c

(951)

on April 17, 2012
at 12:52 PM

What about gut flora? Does the bacteria in your gut help to break down the sugars? The fiber in the fruit feeds them.

510bdda8988ed0d4b0ec0b738b4edb73

(20888)

on April 17, 2012
at 03:14 AM

nope, that's glycemic load: http://en.wikipedia.org/wiki/Glycemic_index vs http://en.wikipedia.org/wiki/Glycemic_load

Medium avatar

(10611)

on April 17, 2012
at 02:46 AM

Glycemic index is not normalized to a constant carb dose. It's a measured glycemic response to eating a serving, and the g of carbs can vary. It's not the response to 2-1/2 apples or 1/3 of a glass of milk. The only thing normalized is 50g glucose as a control, which typically results in 100 index value.

A3bb2c70384b0664a933b45739bac32c

(951)

on April 16, 2012
at 10:18 PM

Thanks for a complete answer. My grandfather was diabetic, so things like this interest me.

Medium avatar

(10611)

on April 16, 2012
at 07:41 PM

University of Sydney protocol is 10-50g carbs, and from what I've seen is often driven by meal portion. http://glycemicindex.com/about.php

D12142c8cafb16d9af10b3362cb8fb62

(1590)

on April 16, 2012
at 07:12 PM

I've eaten 1kg of dates in one go... anything is possible if you unlock your ancestral DNA influx matrix with $248 a month worth of sitting in a cold tub.

B0fe7b5a9a197cd293978150cbd9055f

(8938)

on April 16, 2012
at 05:51 PM

Dave S., what's your point? Nothing of what you say confirms oranges are better whole than juiced and strained.

510bdda8988ed0d4b0ec0b738b4edb73

(20888)

on April 16, 2012
at 04:40 PM

No it's by fixed carb load (and I'm pretty sure they use 50g, but that doesn't matter as long as you know the quantity). Glycemic Load is by fixed portion which is more meaningful in the real world.

A968087cc1dd66d480749c02e4619ef4

(20436)

on April 16, 2012
at 02:15 PM

Fruit vs juice is like, well, apples and oranges.

A968087cc1dd66d480749c02e4619ef4

(20436)

on April 16, 2012
at 02:14 PM

Well, yeah. Also, one glass of juice could be like 4 oranges. You can drink a glass of OJ in a minute. How fast can you eat 4 oranges? Would you eat 4 oranges? And the fiber slows digestion down somewhat.

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5 Answers

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1
510bdda8988ed0d4b0ec0b738b4edb73

(20888)

on April 16, 2012
at 04:39 PM

First you need to know what the glycemic index is. There are a couple of parts to it. I'll skip to the punchline now if you don't want to read everything below: I think it's a meaningless value unless you're a T1 diabetic and need to know how to preload insulin for a meal.

Let's start with the definition of glycemic index: For a given quantity of carbohydrate (usually 50g), the the blood glucose is measured for 2 hours and the area under the curve is called the glycemic index. A glycemic index of 100 is given to 50g of pure glucose, everything else is relative to that (so table sugar or HFCS should have a glycemic index of about 50, which they do).

Note that they only measure for 2 hours and use that value. That may be reasonable in many cases, but for some foods (like wheat bread and wheat pasta), the glucose load can last up to 6 hours (see "Wheat Belly" for the details).

Also, note, that the glycemic index is normalized off of a fixed carb load (50g). That means that it's not useful when comparing different things. Looking at your fruit / fruit juice example. It's reasonable to believe that one piece of fruit is a serving (apple, orange, etc). Now, have you ever juiced a fruit? How much juice do you get from one piece of fruit? I know at my local fancy hippie fresh-squeezed juice bar down town it takes 6 oranges to make a 4 oz glass of juice (and that's where all of the carbs are). According to fit day, one apple has about 20g of carbs, so that means it takes 2.5 apples to come up with 50g of carbs. And one 12oz glass of apple Juice has 50g of carbs. So if you're comparing glycemic index you have to compare 12oz of juice and 2.5 apples (multiply and divide by the serving you're actually having to see the relative numbers).

Finally, glycemic index only measures the glucose load, so a bag of fructose would have a glycemic index of 0. That's why things like agave nectar are called "low glycemic" even though they have tons of sugar.

Basically, view glycemic index as "for the 2 hours after eating enough of this food to make 50g of carbs, how much glucose is in my blood". That's all that it means.

A3bb2c70384b0664a933b45739bac32c

(951)

on April 16, 2012
at 10:18 PM

Thanks for a complete answer. My grandfather was diabetic, so things like this interest me.

Medium avatar

(10611)

on April 17, 2012
at 02:46 AM

Glycemic index is not normalized to a constant carb dose. It's a measured glycemic response to eating a serving, and the g of carbs can vary. It's not the response to 2-1/2 apples or 1/3 of a glass of milk. The only thing normalized is 50g glucose as a control, which typically results in 100 index value.

510bdda8988ed0d4b0ec0b738b4edb73

(20888)

on April 18, 2012
at 03:16 AM

From here: http://www.fao.org/docrep/W8079E/w8079e0a.htm "The glycemic index is defined as the incremental area under the blood glucose response curve of a 50g carbohydrate portion of a test food expressed as a percent of the response to the same amount of carbohydrate from a standard food taken by the same subject. The italicized terms are discussed below because the methods used to determine the glycemic index of foods and to apply the information to diets may profoundly affect the results obtained." But if you don't believe me, google "Glycemic Index Definition" and you'll see

A3bb2c70384b0664a933b45739bac32c

(951)

on April 17, 2012
at 12:52 PM

What about gut flora? Does the bacteria in your gut help to break down the sugars? The fiber in the fruit feeds them.

510bdda8988ed0d4b0ec0b738b4edb73

(20888)

on April 17, 2012
at 03:14 AM

nope, that's glycemic load: http://en.wikipedia.org/wiki/Glycemic_index vs http://en.wikipedia.org/wiki/Glycemic_load

Medium avatar

(10611)

on April 17, 2012
at 09:52 PM

@miked University of Sydney tests GI, Wiki doesn't. Follow the link and read the explanation of the methodology for testing GI, and look at how specific foods were tested. The portions/carb contents vary greatly from food to food. Foods with high carbohydrate content per portion - like rice - have high GI, while foods with low carbohydrate content - like yoghurt - have low GI. You can call it glycemic load if you like but Sydney calls it GI.

510bdda8988ed0d4b0ec0b738b4edb73

(20888)

on April 17, 2012
at 03:08 PM

That would be implicitly taken into account because the glycemic index measure blood glucose, so if it never gets to the blood, it's not there to be measured. However, I don't think our guts (compared to other primates) do much in fermenting sugars for fuel. It's very minor compared to everything else.

2
E5c7f14800c5992831f5c70fa746dc5c

(12857)

on April 16, 2012
at 02:10 PM

Is it because your body does not have to extract the sugars from the fiber?

Yes

E5c7f14800c5992831f5c70fa746dc5c

(12857)

on April 17, 2012
at 03:50 PM

I can eat 4 oranges as fast as I can drink 4 oranges worth of juice. It's extremely easy to eat oranges very fast if you juice them in your mouth :) If you calculate juicing into the time it takes to eat, just eating them is faster.

D12142c8cafb16d9af10b3362cb8fb62

(1590)

on April 16, 2012
at 07:12 PM

I've eaten 1kg of dates in one go... anything is possible if you unlock your ancestral DNA influx matrix with $248 a month worth of sitting in a cold tub.

A968087cc1dd66d480749c02e4619ef4

(20436)

on April 16, 2012
at 02:14 PM

Well, yeah. Also, one glass of juice could be like 4 oranges. You can drink a glass of OJ in a minute. How fast can you eat 4 oranges? Would you eat 4 oranges? And the fiber slows digestion down somewhat.

B0fe7b5a9a197cd293978150cbd9055f

(8938)

on April 16, 2012
at 05:51 PM

Dave S., what's your point? Nothing of what you say confirms oranges are better whole than juiced and strained.

E5c7f14800c5992831f5c70fa746dc5c

(12857)

on April 17, 2012
at 03:51 PM

Glycemic index isn't based on how fast you can eat something though, so I don't really get your point?

0
47d6c23b03dc8a772c2276fa549bd3ae

(25)

on July 17, 2012
at 07:22 AM

It's relative - higher GI simply means the carbs in the fruit juice hit your blood faster than the carbs in the fruit. Per gram of carbs, both relative to pure glucose.

0
Medium avatar

(10611)

on April 16, 2012
at 04:36 PM

GI is based on fixed portions, 100g if I remember right. 100g of juice is nearly all digestible sugars, while 100g of fruit contains a lot of indigestible fiber which has 0 glycemic response.

510bdda8988ed0d4b0ec0b738b4edb73

(20888)

on April 16, 2012
at 04:40 PM

No it's by fixed carb load (and I'm pretty sure they use 50g, but that doesn't matter as long as you know the quantity). Glycemic Load is by fixed portion which is more meaningful in the real world.

Medium avatar

(10611)

on April 16, 2012
at 07:41 PM

University of Sydney protocol is 10-50g carbs, and from what I've seen is often driven by meal portion. http://glycemicindex.com/about.php

0
77877f762c40637911396daa19b53094

(78467)

on April 16, 2012
at 04:00 PM

Like Cliff said -

Yes.

Also worth noting that most(?) juice is cooked and treated with enzymes .

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