Let me preface this question by saying I'm a huge fan of fruit. I eat a fair amount on a daily basis to no apparent ill effect, and I think fruit has been shown to be healthy and safe.
I always see this idea repeated: the fiber in fruit slows the absorption of fructose by the liver, thus negating harm. The fiber is the antidote, or something to that effect. I think maybe this started with Lustig, or at least that's when I began hearing it everywhere.
But is it true? I've never seen it substantiated. Can anyone point to references showing that it is specifically the fiber in fruit that makes the fructose tolerable?
Well, I doubt there's a study that shows that it's specifically the fiber. But there are numerous studies that show that (within reason) eating fruit (they often call it "natural fructose" and I HATE hate term) is OK (and sometimes good) for you and that eating sugar or HFCS (which has "raw fructose") causes lots of problems. So it's at least "something" in the fruit that makes it safer to eat. You just have to look at the results from a bunch of studies, as there's no one single study that will tell you what you want to know. (Side note: often that's where we as a community get tripped up, we try to find "the single study" that shows us what we want to know. That's never going to happen, you just need to read all the stuff that's out there and pick the good science from the bad science and then put the collection of knowledge together yourself - The Quilt does a lot of this for us).
My thoughts 1) a single piece (or single serving) of fruit takes a while to eat and it takes up a pretty big volume in your stomach, so you're not taking in a huge volume of fructose when you eat fruit - unlike fruit juice which concentrates that fructose load. 2) fruits are packed full of antioxidants, it's those antioxidants which protect the fruit itself from the fructose (it's a highly oxidative compound), so when you eat fruit, you're also eating the protection from the fructose. 3) just the presence of fiber will slow down digestion because your gut just has more stuff to deal with. By just purely physical reasons the fructose will be absorbed more slowly and hit the liver more slowly so that it can more safely deal with the fructose.
The only way that fiber could slow the absorption of the sugar in fruit would be if it entirely encapsulated the sugar. This would be discounted by the amount that you've chewed the food and how long it takes stomach acid to pierce the fiber shell. Either way, though, you will be introducing sugar into your system. Come to think of it, the glycemic index of fruit is probably a good way to examine this.
The great value of fruit over fruit juice is the inability to grossly overindulge in sugar, because it is much harder to eat six oranges than it is to drink one glass of OJ.
This is simply my experiences as someone who is insulin resistant and has to be careful of what they eat in order to not experience blood sugar drops. Fruit has never caused me any problems, but fruit juices do, which makes me think that the fiber does help.
HFCS does cause me problems though and it's especially noticeable now that I am limiting my carb intake. Even a small amount of HFCS-containing ketchup will make me feel hungrier, but I can eat home made ketchup made with honey with no issues at all. I'm not sure biochemically what makes it affect me differently, but it does.
on a related note posted by TURKEYTYME, most mainsteam ketchups would make you hungrier not just because of the HFCS, but because of the hidden MSG. Heinz is the worst. MSG is hidden under "natural flavors" and "spices" in order to sound like a "clean label" free of MSG. MSG is an neurotoxin as well as well as increases one's appetite.
You may find this interesting.
It's a video called "Sugar the bitter truth"
It's long, but it breaks it down to the molecular level of what happens in the liver. It turns out, that the fiber in fruit buffers the way insulin responds to the fructose in fruit. Fruit juice is bad because it has no fiber. The MD states that fruit juice is natures way of getting us to eat fiber. Our food supply has been frankenized to increase profits.
The transcript is online too.
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