Fructose in diet expands the surface of the gut and promotes nutrient absorption

https://www.nature.com/articles/d41586-021-02195-1

by gmays • 5 years ago

239 141 5 years ago

hirundo• 5 years ago

Why isn't the increased nutrient absorption offset by decreased appetite and intake? Is there something special about fructose on the demand side as well as the supply side, somehow suppressing normal energy homeostasis?

PragmaticPulp4• 5 years ago

Your body is going to absorb the nutrients one way or another. High fructose doses are changing how those nutrients are absorbed in ways that aren’t beneficial. You don’t want a rapid spike of fructose absorption pumping unprocessed fructose into your bloodstream, as they observed.

ncmncm7• 5 years ago

If you don't absorb things too fast, they reach and feed your gut microbes -- which need it. And, you need them.

jhayward• 5 years ago

Appetite is only loosely related to caloric intake.

com2kid• 5 years ago

To give an example, our bodies seem to almost completely ignore liquid calories from sugar.

That is why it is possible to consume a literal 1000 calorie frappuccino and not feel the slightest bit full.

anigbrowl• 5 years ago

I'm gonna guess because for most of history few people were able to get a massive amount of fructose at once and so there wasn't much evolutionary pressure to select for that.

A bit like an exception nobody thought about while designing the code and so never wrote a handler for.

Arbalest• 5 years ago

Because evolution doesn't work to produce good solutions, just good enough ones. For example, your body works out it is in a low oxygen environment by sensing an elevated amount of carbon dioxide, not measuring oxygen levels. As such, it feels painful when you hold your breath, but going into a room with only nitrogen won't make you feel anything, except maybe breathe faster.

DoreenMichele3• 5 years ago

A. Needs the usual disclaimer "in mice" added to the title.

B. It's not as simple as the title seems to suggest and I like this section for summing up a nutshell "good news, bad news" take on this:

Evidence has emerged5–8 that the small intestine acts as the gatekeeper for the mammalian body against the harmful effects of fructose, the main one being the aberrant accumulation of fat (termed steatosis) in the liver. Moderate amounts of fructose — for example, those ingested when consuming fruits — are taken up and broken down by intestinal cells. Excess amounts, such as those that might be ingested after drinking a sugary beverage, overwhelm the intestine’s absorptive capacity and the fructose either ‘leaks’ into the bloodstream to reach the liver intact, or it spills over from the small intestine and reaches the colon5.

PragmaticPulp4• 5 years ago

It's not as simple as the title seems to suggest and I like this section for summing up a nutshell "good news, bad news" take on this:

The paper isn’t suggesting this is good news at all. The observed modifications to nutrient absorption were largely negative.

The intestines don’t actually have a problem absorbing nutrients. The problem is that excess fructose can disrupt how quickly those nutrients are absorbed, which causes problems.

In this case, the increased nutrient absorption isn’t a good thing.

DoreenMichele3• 5 years ago

I have a condition that actively interferes with nutrient absorption. It's why I bothered to read this at all.

andy_ppp2• 5 years ago

I’m so tired of this “in mice” meme, it tells us nothing about how accurate the predictions can be made from these experiments. Can everyone just assume “in mice” is the default and in humans the exception? We do experiments in mice because so much is the same between mammals.

DoreenMichele3• 5 years ago

We do experiments in mice because they are cheap, most people don't care too much if you kill them and dissect them, it's actually quite hard to get meaningful data from humans and a violation of a bunch of medical ethics stuff to do similar experiments in humans.

I happen to think "in mice" matters. We don't really know how well that translates and I read medical research pieces because I have a serious condition. For me, the stakes are fairly serious. Killing or not killing me is not hypothetical. It's very real.

kortex2• 5 years ago

Mice/rats are a decent model, you just have to know how to extrapolate:

- toxicity - rats are actually pretty good once you correct for metabolism (divide LD50 by 6). Humans and rats consume lots of xenobiotics due to our versatile diets

- neuroscience, anything below the prefrontal cortex is pretty well conserved between rats and primates

- cancer - kinda garbage. Mice and rats get cancer at the drop of a hat. But if it doesn't give rats cancer, that's a really good indicator of safety

- exercise - generally extrapolates pretty well

The worst is probably things like higher neuroscience, Alzheimers, and diet. Mice in particular are more vulnerable to high fat and high sugar diets than humans. It's fairly easy to induce diabetes in mice, but again, useful in that it increases sensitivity. But also means anti-diabetes drugs may have exaggerated effects.

PragmaticPulp4• 5 years ago

To clarify: The increased nutrient absorption they observed wasn’t actually a good thing. Our stomachs evolved to very efficiently extract as many nutrients as possible from the food we eat, so these nutrients weren’t being wasted. Rather, the excess fructose overwhelmed the normal nutrient breakdown process and resulted in an abnormal nutrient absorption pattern:

Moderate amounts of fructose — for example, those ingested when consuming fruits — are taken up and broken down by intestinal cells. Excess amounts, such as those that might be ingested after drinking a sugary beverage, overwhelm the intestine’s absorptive capacity and the fructose either ‘leaks’ into the bloodstream to reach the liver intact, or it spills over from the small intestine and reaches the colon

Basically: Too much fructose at once, especially without all of the fiber and structure of fruit to slow it down, ends up in places it shouldn’t because the normal digestive processes can’t keep up. Spilling bursts of fructose into your bloodstream and your liver isn’t great for your body.

Excess Fructose spilling into the colon creates another set of problems as this can do weird things to the microbiome. Ideally the small intestine would be able to handle the fructose and leave the colonic bacteria to feed on the leftover complex carbohydrates, but if you eat too much fructose some of it spills into the colon.

fiddlerwoaroof4• 5 years ago

What I don’t understand about these articles is the focus on HFCS: as I understand it, honey contains the same or more fructose per unit as HFCS, but these articles never seem to address whether we observe the same effects with it.

gumby• 5 years ago

HFCS is common in the American diet; honey much less so.

TylerE• 5 years ago

Per capita consumption of HFCS = 38lbs.

..... of honey = ~1lb (and that seems high to me, personally)

beowulfey• 5 years ago

I would say honey vs HFCS is similar. A big reason why HFCS is no good is the raw fructose is easily absorbed (as mentioned) whereas sucrose is a dissacharide that must be broken down (which does not happen as quickly).

The big difference in HFCS vs honey is the quantity that we are exposed to in processed foods. If they replaced all HFCS with honey, I can't imagine it would be very different.

HFCS: 55% fructose, 45% glucose

Sucrose: 50% fructose, 50% glucose

Honey: 50% fructose, 40% glucose, 10% maltose (dissacharide of two glucose molecules).

richcollins• 5 years ago

There are hunter gatherers (hadza, ache, pygmies) that eat substantial amounts of honey without becoming overweight.

maxerickson2• 5 years ago

Sucrose is rapidly converted into glucose+fructose also.

floatingatoll7• 5 years ago

The general health limit for sugar for a person is approximately one small can of Coke per day or less, with no other added sugar anywhere your diet at all. That’s two or three tablespoons of honey or HFCS.

Replacing HFCS with honey is probably technically better for you, but chances are, if you’re an American, your consumption is probably way beyond that limit, and changing out HFCS for honey or sugar won’t make anywhere near enough of a difference to matter.

Avoiding HFCS is good practice for avoiding sugar, but ultimately you should just focus on limiting added sugar at this point and not worry so much about what kind it is. (Especially if you live in America, where the bread on a Subway footlong sandwich has a third of your daily sugar limit in it.)

ps. Fruit juice should be considered water with added sugar, for the purposes of avoiding sugar. Whole fruit is fine enough, since your body knows how to handle overeating fruit.

suyash• 5 years ago

This is why juicing is bad, specially if you consume it too quickly. Smoothies are better but eating whole fruit and vegetables is the best.

another_story• 5 years ago

Is there a difference if you're blending whole pieces of fruit and veg, so you get pulp and all?

dghughes• 5 years ago

Our stomachs evolved to very efficiently extract as many nutrients as possible from the food we eat,

I'm pretty sure the stomach just breaks down food with acid it's then passed along to the intestines which absorb the nutrients.

slumdev• 5 years ago

It's even more complicated than that. Some nutrients are absorbed in the stomach. Most are absorbed in the small intestine. Some are absorbed in the large intestine.

Heck, some are even absorbed through the mouth and gums!

senectus1• 5 years ago

This is pretty important information for those finding themselves in the FODMAP division of intestinal issues.

dazag• 5 years ago

Foods with highest levels of fructose are mostly ready-to-eat cereals.. Always promoted as healthy, is probably one of the worst things you can do in the morning... It will set a roller coaster for the rest of the day

grecy2• 5 years ago

Given that we know the sugar industry paid scientists to blur sugar's role in heart disease [1], and that the whole "eating pyramid" was essentially bought and paid for by industries that just wanted to sell more of their product, how can we ever trust stories like this again?

How can a regular person actually know if articles are "truth" or "paid for truth"

[1] https://www.theguardian.com/society/2016/sep/12/sugar-indust...

helicalspiral• 5 years ago

why would the sugar industry fund a study that says that HFCS is bad?

grecy2• 5 years ago

I wasn't suggesting the sugar industry is behind this one, but asking the general question of how do we know there isn't someone funding the results they want.

snet0• 5 years ago

How can a regular person actually know if articles are "truth" or "paid for truth"

Reading the article might help.

bcatanzaro4• 5 years ago

The summary was irritating because it mentioned HFCS over and over as if it is the cause of excessive fructose consumption. But most HFCS is either 42% or 55% fructose, while ordinary table sugar (sucrose) is 50% fructose.

It seems to me that overconsumption of sucrose is just as bad for you as HFCS, in which case focusing attention on HFCS is harmful. People will drink Mexican Coca-Cola made from sucrose and think it is better for them because of this article.

PragmaticPulp4• 5 years ago

They ran the experiment with HFCS, so that's what they used in the conclusion.

In practice I wouldn't expect different results with a bolus of table sugar. However, they didn't test that so they didn't make any claims about it. Mostly just being scientifically accurate.

bcatanzaro4• 5 years ago

Yeah I think so too. But it’s unfortunate because people demonize HFCS for cultural reasons and this article just makes it worse. Like I said, drinking a Mexican coke isn’t going to result in significantly less fructose in your intestine. Even if I do agree that it tastes better. :)

User23• 5 years ago

It's remarkable how different pure dextrose/glucose/grape sugar lozenges make you feel than fructose candies.

I wonder why l-glucose has never been used as an artificial zero calorie sweetener.

Edit: expensive is a lame reason. Sugar isn’t the dominant factor in pricing and hasn’t been for quite a while. There’s a huge population of affluent consumers who would gladly pay a large premium for an authentic zero calorie sugar taste.

bcatanzaro4• 5 years ago

Because it’s expensive to make since it’s incompatible with normal biological production.

kortex2• 5 years ago

Tagatose can be produced relatively easily and has 38% of the caloric content.

https://en.m.wikipedia.org/wiki/Tagatose

fiddlerwoaroof4• 5 years ago

Not only table sugar: as I understand it, these results should be replicable with honey (and maybe agave syrup?) too. It really seems to me that a lot of health articles are systematically deceptive about the relative issues with HFCS vs. other sweeteners.

_yoqn3• 5 years ago

Honey does have slightly less fructose in it (IIRC ~40%). And it does contain beneficial micronutrients. But mostly it's just as "bad" for you as cane sugar or HFCS.

torstenvl2• 5 years ago

Table sugar does not "contain" fructose, just like consuming table salt isn't like throwing a chunk of sodium down your throat.

More directly, sucrose consumption isn't likely to result in a buffer overflow of fructose because your body regulates the breakdown of sucrose via sucrase production.

bcatanzaro4• 5 years ago

If sucrase production was limited people would be able to easily poison themselves by eating too much sucrose. Sucrose intolerance from sucrase deficiency seems pretty rare though and I’ve never heard that your body regulates the breakdown of sucrose. Seems rather that the body makes how ever much sucrase is necessary to make sure the enzyme is not the limiting factor.

I think to a first order, sucrose really is 50% fructose to the human body.

scoofy• 5 years ago

6. Could the real culprit in fatty liver disease be high-fructose corn syrup, not regular table sugar? After all, it says "high-fructose" right on the label.
Regular table sugar is made up of about 50% fructose, and a common formulation of high-fructose corn syrup (called "HFCS-55") contains 55% fructose. These products are similar enough that there is no evidence of differences in their impact on metabolic health. However, some commercially available formulations of high-fructose corn syrup contain higher proportions of fructose, such as 65% or even higher.21 We do not know whether the health consequences of these products differ from products containing lower concentrations of fructose.

UCSF researchers seem to suggest that this isn't actually relevant

https://sugarscience.ucsf.edu/alternate-views-toxic-truth.ht...

phonypc3• 5 years ago

Undigested sucrose in the large intestine causes bloating, flatulence, diarrhea etc. Doesn't happen in normal circumstances. It's all rapidly broken down into glucose/fructose.

uplifter• 5 years ago

In addition to overall fructose levels, its suggested that the ratio between glucose and fructose levels may be important for determining the changes to the nutrient absorption pattern.

Figure 1 of the linked article illustrates a model by the study authors concerning the effects of glucose vs fructose on gut morphology and nutrient absorption pattern. As described in the caption, fructose up-regulates (ie stimulates) a biochemical pathway that leads to changes in the gut which cause increased nutrient absorption and lipid (ie fat) synthesis, but glucose down-regulates that same pathway.

Put simply, fructose and glucose compete antagonistically to either promote higher nutrient absorption or lower it, respectively. One pushes the lever, the other pulls it, and the ratio will determine who wins. The linked summary article does not, however, state what the relationship between ratio and degree of effect is.

slicktux• 5 years ago

Yea but sucrose is different molecularly; the Glucose and Fructose are bonded whereas HFCS it’s a mixture of the two… so the former the body has to metabolize it while the latter it does not. So calorie intake is higher and fructose and glucose are absorbed faster and at higher amounts.

istorical• 5 years ago

The food pyramid used in the western world misled people to believe fruit is a necessary component of a diet. It absolutely isn't. Vegetables give you all the dietary components without the high amounts of sugar. And if you eliminate all simple sugars / obvious bad carbs from your diet, then eventually stuff like sauteed carrots / corn, beets, etc. starts to taste 'sweet' to your reset tastebuds.

chapium2• 5 years ago

Produce literally tastes different in the US when compared to other countries. My guess is that these shelf stable varieties which are more bland aren’t used elsewhere.

caeril2• 5 years ago

To say nothing of the fact that modern "fruits" bear little resemblance to the fruit available to us through much of our evolutionary history.

We've bred, selected, and engineered "fruit" for sweetness, size, yield, and color to an enormous extent over the past 500 years or so, with the majority of that acceleration occurring in the last 100.

ncmncm7• 5 years ago

AND bred the fiber entirely out of, specifically, grapes.

Remarkably, no other fruit lacks fiber.

phonypc3• 5 years ago

To be clear, carrots, corn and beets taste sweet because of not-insignificant amounts of simple sugars. Especially cooked.

asdfasgasdgasdg• 5 years ago

While that may be true, I don't think most American sugar consumption comes from fruits. I guess if Americans switched to snacking on fruit rather than processed foods, even if we ate the same mass of snack food, it would be good for the average person's diet. There's no need to demonize fruit at this juncture -- maybe later when that is the most unhealthy thing people are eating.

(Personally I'm on a kick-the-dad-bod diet right now -- all I've done is try to eat 2x as much veg each meal, stop drinking, switch most snacking to apples, and put a little quarter cup measure in any bags of snack food I happen to have in the house. Down 13lb since early July on a not terribly fat baseline. For me, fruits have been very helpful as they seem to give a good contribution to satiety, while being less calorically intense than what I was snacking on before.)

CaptainSandwich• 5 years ago

This study is about consuming HFCS by itself. My understanding, at least based on the studies referenced in “How Not to Die”, is that the fiber in fruit more than makes up for the high sugar content.

I agree in general, though, that much of the processed food we get in the US is oversweetened or oversalted, and it totally distorts the palate.

cableshaft• 5 years ago

Maybe not necessary, but one type of fruit you should probably still consider are berries. Most are pretty low carb but pack a lot of nutrients in them. I'm on a pretty big blackberry kick myself right now (having at least one serving a day).

Even keto diets allow for eating berries in moderation. That's actually how I started getting into eating berries again, when I was doing keto (I'm not currently).

https://www.dietdoctor.com/low-carb/keto/fruits

hack-news2• 5 years ago

This is the worst diet advice I've ever read. The problem is not corn, carrots, or beets in any person's diet.

I eat fruit all the time, 2-3 types a day, and I am very strong and physically fit.

shadowgovt• 5 years ago

Someone update the Twitter list.

https://www.twitter.com/justsaysinmice

_yoqn3• 5 years ago

Keep this fact in mind as well: "Regular" cane sugar (sucrose) is made of 50% fructose and 50% glucose. Your cells only use the glucose and the fructose has to get metabolized.

mysterypie• 5 years ago

Today I learned that, “Sucrose is made up of one molecule of glucose and one molecule of fructose joined together.(Wikipedia)”. A basic fact, but I didn’t know that.

Fructose in diet expands the surface of the gut and promotes nutrient absorption

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