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Dr. Lustig on Fruit Fructose A More Nuanced View

#1 User is offline   Michael R 

Posted 02 March 2012 - 02:08 PM

Many folks have seen this informative and quite disturbing video about the metabolism and deleterious health effects of fructose by UCSF's Dr. Robert Lustig:



... or read his recent, "controversial" editorial on fructose in Nature, and a related New York Times piece on sugar by Gary Taubes, which relies heavily on Lustig's views. For a detailed review in which Lustig lays out his concerns about fructose's health and metabolic effects, see (1).

Lustig often volunteers, or is asked for, his views on fructose from fruit, as vs. that from added sweeteners, and until yesterday every time I've heard him present his view, it's been that we shouldn't worry about it. He's generally offered two reasons for this seeming inconsistency: first, that the sheer quantity of fructose (including the half of fructose) in fruit is very small and the package large, making consumption of fructose from fruit somewhat self-limiting. The other, of which I'm skeptical, is that even on a gram-for-gram basis, fructose in fruit isn't going to have the same metabolic wallop on the liver as that in a soda or candy bar, because the fiber will slow its absorption. The reason for my skepticism is that when you look at the GI of nearly all fruits -- which indicates how quickly glucose itself, and also glucose released from the liver following fructose conversion to glycogen and subsequent release as glucose -- you see that they can be predicted almost exactly by simply tallying up the (GI x (mg individual sugar)) of all carbohydrates in the fruit, and then dividing by the total mg of all sugars; the fiber just doesn't seem to impair sugar absorption worth a spit.

Yesterday, in a wide-ranging and occasionally surprising interview on a local NPR affiliate, Dr. Lustig admitted (with self-confessed hesitancy over the unintended consequences of the admission) to some nagging doubts about his carte blanche on fruit, and says he is now testing the effects of fructose from fruit as part of total fructose intake (relevant section begins at 35:34 on the mp3):

Quote

You've actually just asked a very loaded question (and I'm sure you didn't mean to). But this is a very complex thing, and I do not want to be known as someone who comes out against fruit in any way, shape, or form. Because ultimately, in terms of the panoply of choices in the store, you know, fruit is so much better than so many of the others, that I don't want to, uh, you know, give listeners the impression that fruit is a major problem. However, there are some reasons to be concerned about the total amount. And there are some, uh, evolutionary studies done in primates, and there are also some things that we are doing, in terms of the total diet of the world, using the Food and Agriculture Organization statistics database, linking that to the International Diabetes Federation database, and we see some uh, very clear, um, ah, issues about too much fruit.

So, I'm not real excited about saying that in public; you're sort of asking directly. I think that fruit is so much better a choice than virtually anything else in the store -- particularly any processed food -- that I don't want to come down on it. But I would say, fruit is one of those things where I would say, everything in moderation.

Host: Well, and if [our caller] is saying, "Can I have an apple and a banana and a pear in a day, would you say ...?

I think that's fine. Lots of fiber. [...]

The fact is that [in human history], we as humans only had fruit once a year. And that was called harvest time. And then, what happened after harvest time was four months of winter. So in fact, the sugar that we consumed during that month after harvest time, actually increased our adiposity in a way that was adaptive and beneficial, given that we were about to face four months of famine. The problem is that now -- with sugar being available 24/7, 365, and that the total sugar consumption has just gone up everywhere, and very specifically for the food industry's purposes -- that we have basically undone our evolutionary biochemistry in a very negative way. What we have now is maladaptive.


He made that last point, in almost the same words, on NPR's Science Friday:

Quote

We as human beings really only had sugar available to us one month a year, it's called harvest time. And the fruit would fall to the ground, we'd gorge on it, consume it like crazy. That would increase our adiposity, it would increase our fat stores very specifically.

And then what would come after that? Four months of winter, no food at all. And so putting on those extra pounds in advance of a four-month famine was actually adaptive and actually let us make it through winter so that we could repeat the cycle all over again. It was actually metabolically and evolutionary adaptive.

The problem is that we now have a maladaptive situation because sugar is available 24/7, 365 in amounts that has never been known to man previously. How do we know this is true? Because the orangutans in Papua New Guinea have what are known as masting fruit orgies every January when harvest time comes, and the food falls to the ground, and they do exactly the same thing.


This does seem to be an exaggeration: per one source, while orangutans do indeed get nearly 100% of their Calories from fruit in January, orangutans still get 21% of their food energy from fruit in May.

It's clear, IAC, that you can get significant amounts of the stuff from fruit, even on a healthy diet with no added sweeteners. NHANES data on fructose consumption by Americans shows that, aside from a disconcertingly-high intake in teenaged and early-adult males, and a conservative habit in people ≥51 y, the average American consumes ~50 g of added fructose/d, and 8 g of naturally-occurring fructose (of which, surprisingly, average Americans get more fructose from grains than from fruit and fruit juices). But at 10.5 g per apple, eg, a person could match the total fructose consumption from added sugars of an average American with 5 apples a day. And there's 16 grams of fructose in a cup of pomegranate juice, and 18.6 g/C in grape juice -- surprisingly, much more than the 6 g/C of orange juice.

Reference
1: Lim JS, Mietus-Snyder M, Valente A, Schwarz JM, Lustig RH. The role of fructose in the pathogenesis of NAFLD and the metabolic syndrome. Nat Rev Gastroenterol Hepatol. 2010 May;7(5):251-64. Epub 2010 Apr 6. Review. PubMed PMID: 20368739.

This post has been edited by Michael R: 02 March 2012 - 02:30 PM


#2 Guest_Marcus Martinez_*

Posted 10 March 2012 - 07:24 AM

I just crunched my diet through nutritiondata looking for fructose content in the vegetables group. peppers (especially red ones) tomatoes, onions and cabbages rate rather high. I calculated that my average daily intake of vegetable-derived fructose amounts to 20g-25g a day. So my fructose intake is actually fairly high due to the huge volumes of vegetables I eat every day. This makes me think...

#3 User is offline   Taurus Londono 

Posted 12 March 2012 - 10:05 AM

View PostMarcus Martinez, on 10 March 2012 - 07:24 AM, said:

I calculated that my average daily intake of vegetable-derived fructose amounts to 20g-25g a day. So my fructose intake is actually fairly high due to the huge volumes of vegetables I eat every day. This makes me think...


IMHO, I would *not* necessarily call 20-25g of fructose "high", even on a CR diet....unless you're on 1,000 calories a day...

Also, how did you come to the conclusion that cabbage rates high in fructose?? I just looked it up in cronometer; raw cabbage has ~0.058g fructose per calorie!
In other words, if you ate 2,000 grams of cabbage, the equivalent of 28(!!!) 8oz cups of shredded cabbage, you would still get LESS fructose than ~2/3 of a single cup of raisins.
That's doesn't qualify as "high" IMO.

AFAIK, vegetable fructose is entirely negligible, a non-issue PRIMARILY because there's so darn little of it in the vegetables to begin with. At any rate, it would be vastly outweighed by the benefits of the vegetables themselves (as far as I can imagine, at least). Let's not worry about onions and cabbage, folks.

This post has been edited by Taurus: 12 March 2012 - 10:07 AM


#4 Guest_marcus_*

Posted 14 March 2012 - 02:47 AM

Hi Taurus,

I am just surprised of the amount of fructose you can actually ingest without touching fruit or any other non-CR-friendly food. I didn't expect it to be that high. I do for my part eat some grains, but there are probably some who eat vegetables only. And if you ate vegetables only you could easily end up with 50g/day of fructose intake from vegetables, so my estimation.

my conclusion that cabbage rates high refers to the ranking in the table in nutritiondata if you sort for fructose content in the vegetables group.
I have these numbers from nutritiondata using the nutrient search tool.
peppers, sweet, red, raw: 2380mg/100g
onions, sweet, raw 2020mg/100g
cabbage, red, raw 1480mg/100g
tomatos, red, raw 1380/100g
broccoli, raw 630mg/100g

lets say someone eats 6 bell peppers (a 150g each), 200g onions, 500g tomatos, 500g cabbage, 200g broccoli a day, one ends up with 41220mg fructose with a caloric intake of about 700kcals.
(sorry, I'm not good with "cups" and "ounces"... )

It just made me think, I am not worrying.

#5 User is offline   Taurus Londono 

Posted 15 March 2012 - 08:05 PM

Fair point but...
That's 2.3 kilos of food...in other words, over 5 lbs...! :blink:
I know some fellow CRONies can eat quite a bit of food (of the low-cal, nutrient-dense variety), but 5+lbs of food in a day and that's only ~700 calories and not nearly enough protein. 5 pounds of food and you're probably not halfway through your calorie intake for the day. Didn't mention beverages yet. Even if you didn't mind the abdominal distension (from the sheer mass let alone the raffinose), I just don't think it's feasible.

I think the bottom line is that the caloric density of the kind of vegetables you cite (though peppers and tomatoes are fruits), the sheer amount of (raw) food you'll have to chew means that it's a moot point. IMHO, if I were you, I would honestly put any concerns about fructose from cabbage or broccoli out of your mind.

This post has been edited by Taurus: 15 March 2012 - 08:09 PM


#6 Guest_Mpadalino_*

Posted 06 August 2012 - 01:21 AM

View PostTaurus, on 15 March 2012 - 08:05 PM, said:

Fair point but...
That's 2.3 kilos of food...in other words, over 5 lbs...! :blink:
I know some fellow CRONies can eat quite a bit of food (of the low-cal, nutrient-dense variety), but 5+lbs of food in a day and that's only ~700 calories and not nearly enough protein. 5 pounds of food and you're probably not halfway through your calorie intake for the day. Didn't mention beverages yet. Even if you didn't mind the abdominal distension (from the sheer mass let alone the raffinose), I just don't think it's feasible.

I think the bottom line is that the caloric density of the kind of vegetables you cite (though peppers and tomatoes are fruits), the sheer amount of (raw) food you'll have to chew means that it's a moot point. IMHO, if I were you, I would honestly put any concerns about fructose from cabbage or broccoli out of your mind.


Yes, but I think you're forgetting the many people who juice and drink their veggies in smoothies.

#7 User is offline   Taurus Londono 

Posted 08 August 2012 - 08:26 AM

View PostMpadalino, on 06 August 2012 - 01:21 AM, said:

Yes, but I think you're forgetting the many people who juice and drink their veggies in smoothies.


Even if we assume that using a juicer and discarding the "pulp" is as nutritious as actually consuming a whole vegetable, bear in mind that water makes up most of the mass anyway. You need only look up any vegetable or fruit on CRONOmeter and check the water content. ...and even if you take the chewing out of it, the abdominal distension is still an issue... (and remember, that's only 700 calories; you'd still have to consume more to have a sane calorie allotment for the day) ;)

This post has been edited by Taurus: 08 August 2012 - 08:55 AM


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