Some thoughts on fructose studies

I've been poking about the literature lately ever since the insulinogenic (in terms of circulating insulin levels but not necessarily secretion of insulin) properties of jelly beans were made known to me a while back.  I've been looking into studies comparing sucrose to glucose or fructose separately, or that measure insulin secretion and/or clearance per se.  It's a rough go.  Much of the research that turns up with fructose in the search phrase involves HFCS not fructose per se.  When you get isolated fructose studied, however, there are still other complications. 

For starters, it is impossible to isolate the effect of just fructose with whole foods.  Just about every source of fructose, like fruits, also contains sucrose and even considerable amounts of isolated glucose in many cases.   It is also virtually impossible to attain the levels of fructose generally required to elicit a measurable metabolic response.  For reference, a medium apple contains roughly 10g fructose (most of which is free).  A "bolus dose" for 50g would be difficult to achieve and would come with ~5g glucose per apple.  So ... sweetened beverages it is as the major dietary vehicle by which fructose is incorporated into dietary interventions.

To be fair, this is how many Americans get their excessive fructose.  To those I would summon my best Katie Couric valley-girlish "DUH" and say just stop drinking the crap!  Really, where on the USDA food pyramid or MyPlate or anywhere else has the government or any nutritional organization EVER promoted mass consumption of sodas and other SSB's??   I'm not talking ads by sugar producers, etc.  I'm talking nutritional advice.  Please prove me wrong, but in my lifetime, during which Frosted Flakes used to be called Sugar Frosted Flakes, I don't recall anyone from my pediatrician, to my dentist, to my school nurse, to my health teacher, ever advising me to eat them.   Indeed I can remember these being demonized as poor choices for as long as I can remember.   Sweets are up there with the fats and oils atop the old pyramid.   The only advice I've ever received vis a vis sugar from any authority figure has been to limit, limit, limit.

But it gets worse.  Far too many fructose studies are done in the context of hypercaloric intake -- in other words energy surplus.  The study by Havel's group that Taubes cited recently being one such case.  The subjects not only consumed roughly 150g of fructose for 10 weeks, they did this without compenstion for calories from ordinary intake so that they ate like 300 cal/day more than their energy stable intake.  That's 15 apples for anyone keeping track.  I came across another study recently:  Fructose overconsumption causes dyslipidemia and ectopic lipid deposition in healthy subjects with and without a family history of type 2 diabetes.  In this study they took male offspring of T2's and controls with no family T2 history, and fed them (in random order at different times) either an isocaloric diet (normal) or a hypercaloric high-fructose diet -- this diet was a +35% energy intake in fructose!  Now, granted "overconsumption" was in the title but ...

Now, as Taubes pointed out in his 2002 NYT article, we Americans DO consume more calories than we did in the 70's, and we also consume a lot of those calories in sodas and such.  Not because, as he absurdly suggests, our government and nutrition authorities are sanctioning them as "low fat".  So the overconsumption studies are pertinent to "real life", but they are demonizing a nutrient based on a pathologic eating scenario.  The result is that we're going to spawn a generation of fructophobes who will eschew even fruits.  In our search for the mythical singular cause of all obesity, we're going to finger sugar.  Taubes even says now that we could probably eat all the pasta, bread and rice if only we lay off the sugar.  That's the secret of the Japanese!   He heralds the research into sugar as the devil as being some of that "good science" that's been missing and a few are now doing (at his urging of course).  

Unfortunately, though some of these studies are pertinent to a segment of the population who guzzle SSB's, they are wholly not applicable to the real life scenarios in which most become obese.  I'm not alone in having gotten obese never drinking a regularly sweetened beverage since my mid teens. Sure you have the soda junkies consuming massive amounts of liquid calories and not compensating for solid food calories, but this is not the majority of the population.  If it is, the solution is simple.  Outlaw soda and juice "drinks".  He he .. the libertarians occupying the Insurgency aren't going to like that ;-)  But seriously, limit sweets in general has been around for a long time.  Nobody in their right mind believes the uptick in sugary beverage consumption was because said beverages were low fat.

The other problem with all of these studies is that they separate the fructose from the other things in foods that contain it.  I'm not just talking about the fiber, which is one factor, but fructooligosaccharides (FOS, classed a fiber but no the apple peel type of fiber we usually refer to), vitamins, minerals, phytosterols and such.  At least give real juices a fair shake in this that at least contain some of the "go withs" that are absent from most SSB's.  And on that topic, who knows the contribution of the flavorings and other additives.  These studies usually use flavored beverages, but many recognize plain sugar water is not all that appealing.

So, I'm afraid that in general, I would hang a "bad science" tag around the necks of most fructose researchers.  Not because it's all bad, but on the whole a lot of the studies have limited application to real life scenarios.  To keep some inner city kids from buying a 2L generic cola for a buck, politicians would like to slap an "only few cents per liter" tax on the stuff.  Treat fructose like alcohol and tobacco.  I'm sorry but I'm not the most libertarian person out there, but I'm not the most socially engineering inclined person either.  I think such taxes will only produce more revenues to be pissed away spent on wholly unrelated pet projects while having minimal impact on the consumption behavior and health of the supposed targets they are trying to help.  And to me this is where this science is dangerous.  Because the title of a paper Fructose overconsumption causes dyslipidemia and ectopic lipid deposition in healthy subjects with and without a family history of type 2 diabetes, becomes the headline like:  Sugar consumption causes fatty liver. 

Not sure there's a summary message to this post other than just to "talk out loud" a bit about the state of the science in fructose research.  I keep hearing a lot of misinformation repeated about it -- e.g. that it can't be metabolized for energy so it is all turned to fat, that it raises triglyceride levels because of that, etc.  This has caused some to say we should never eat fructose at all, and at the extreme, for the likes of Lustig to unequivocally deem it a poison with no positive purpose in our bodies.  I think eliminating all fructose just because a 2L bottle of Coke a day habit is not good for you would be as silly as avoiding eggs for fear of raising your cholesterol.