My N=1 30 day fructose elimination showed me that fructose and I do not agree.
This may be the next wheat...we already know how bad fructose is by itself... Are the small amounts in fruit ok for most similarly to how most tolerate wheat before they take 30 days and clear their system
Have you done a self 30 day trial?
A about 2 years ago (after feeling poorly for about 18months), I was diagnosed with Fructose Malabsorption. Once I tuned my diet accordingly, by figuring out what amount of fructose I could tolerate, the change was amazing (back to feeling good, having energy again, and no mood-swings!).
As someone with FM, I can offer the following resources that I've found helpful over the years:
Also, since it has not been mentioned yet, I should also highlight that fructose and fructans (chains of fructose molecules) must be avoided. These are present in Wheat, brown rice, onions, green beans, carrots, asparagus, garlic, and some other stuff (see: http://www.thefartingpear.com/index.php/foodsearch/index/fructans).
This may be the next wheat...
First off, it's not similar to wheat at all since it's an intolerance as opposed to an allergy, i.e. there is no immune response to fructose.
we already know how bad fructose is by itself... Are the small amounts in fruit ok for most similarly to how most tolerate wheat before they take 30 days and clear their system
Many studies to date showing that fructose is deleterious to health have done so with ridiculous/unrealistic doses (25% or more of diet). On top of that, a lot of them have been rodent studies. What you have for evidence is that chowing down >100g of fructose a day will cause metabolic syndrome and other nasties. This would involve eating large amounts of fruit or eating substantial quantities of garbage food like non-diet sodas. This is not useful at all.
YOU might be intolerant of fructose, but it is a total non-sequitur to make the leap to saying that fructose is bad in general, even in small amounts found in real food, without any reference to dosage or context (e.g. pwo nutrition vs. obese people on a hypercaloric diet, etc). This blaming of particular macronutrients as the just-discovered-cause-of-all-our-health-problems is sensational at best (sat fat anyone).
From a paleo standpoint, fructose is prevalent in most vegetables and fruits in varying quantities. We have specific metabolic pathways for fructose absortion (GLUT 5). It is not advantageous to evolve in a direction where we lose our ability to absorb/metabolize fructose.
There is a lot of good information out there, but there are also a lot of alarmists trying to push their own agendas. Vegan dairy bashers come to mind. Some paleo dudes seem to have a hypochondriac like fear of vegetables. Reading the actual studies themselves might be a snore but its important to follow the actual science as opposed to getting caught up with convincing looking pseudoscience or idiosyncratic reasoning.
My digestive system has been screwed up since I was a kid, so I think I have a predisposition for food intolerances. I have a ton of them (many of which are irrelevant with this WOE, thank goodness), fructose malabsorption included. I did a fructose elimination diet a while ago and found I don't tolerate it either. After I cut out all fruit and higher fructose veggies (for a couple months), I started gradually adding fructose-containing foods back in one by one and found I was supper sensitive. I had a reaction after any sort of fruit or higher sugar vegetable (like carrots) I tried.
I think most people can tolerate the small amounts of fructose in fruit. I think after a person clears their system of it, the reaction to fructose will be more pronounced from their perspective because they've gone thirty days without it. Once you realize how good you feel without something you can't tolerate, you notice it more when that something makes you feel terrible. Though I don't know if your tolerance of it actually lessens once you rid it of your system.
ETA: I know I said "tolerance" a lot in my response but fructose malabsorption is, as the name suggests, a malabsorption issue. It's not a tolerance issue.
Fructose Malabsorption Disorder is the inability to absorb fructose and fructans. This condition is NOT characterized by the inability to "tolerate" fructose/fructans. Sufferers of Fructose Malabsorption have no difficulty tolerating fructose/fructans once they have been absorbed. However, inducing absorption is difficult or impossible for FructMal sufferers. The symptoms of the disease are the result of having unabsorbed fructose/fructans in the lower intestine.
I would be cautious about interpreting a 30 day fructose elimination.
I do not know specific details, however many transporters like the GLUT5 that absorbs the fructose from the small intestine are regulated by the presence of the molecule they take up. What this could mean is that if you eat no fructose for a month your ability to absorb fructose could be greatly reduced. Reintroducing it could result in malabsorption and may take a day or two before you can produce new GLUT5 transporters. Thinking you have a malabsoption problem when you don't doesn't help anyone.
Also the absorption of fructose takes place near the tips of the villi of the cells of the small intestine. Any damage to the villi, such as from celiac disease or other gut disease, could reduce the ability to absorb fructose. Maybe any malabsorption problems would improve again with a healthy gut lining.
Fructose malabsoption seems like an interesting new idea and reducing fructose looks like it could be a usefull experiment if you have possible symptoms like IBS.
Seems possible if the fructose uptake mechanism in your intestine is deficient... I would say this seems rare (would be extremely evolutionary unfavorable). Just from personal experience I haven't heard many people complain of loose stool/ excessive gas from eating fruit (via increase of osmotic pressure in the intestines/ bacteria breaking down undigested fructose) If it were getting in your body since it is a simple sugar there is no enzyme which needs to break it down... only an enzyme in the liver which needs to convert it to pyruvate --> glycogen. So, like this website alludes to, I'm hesitant to believe it can be very similar to lactose intolerance. Of course I'm sure there are a handful of mutations in the aldolase which converts fructose into a glycolysis intermediate that decrease its affinity... but it seems that people who suffer from fructose problems typically do so because of a malabsorption issue. If you keep it down you should be fine (I think gluten's a lot worse)
I DO think that this is a very important step in an optimal diet. I just really love fruit... so I eat 10 blueberries and a teaspoon of honey after my workout. Its definitely not necessary and if you can live without it, more power to you. (just don't go crazy on the glucose) Raw fructose is about 1.7x sweeter than sucrose so you can eat a bit less of it for the same punch (heating catalyzes the reaction to a 6 carbon fructose sugar that is about the same as sucrose so it mitigates the advantage). I'm gonna stay with a bit of fructose / day, but if I could ever give up sugar. It would be a good day.
On the evolutionary side: We have specialized transportation systems for fructose (see Glut5 transporter), so I can't say I think it decreases our fitness too much (evolutionarily speaking... although optimal health/ your health goals may need a different analysis)
Large amounts of fructose are not easily digested, usually 50 gr being the maximum most people can comfortably handle.
The ratio between fructose and glucose in fruit is also important, as glucose helps with fructose absorption. If you look at the nutritional values, you can identify (and avoid) fruits that are high in fructose and low in glucose: apples, pears, melons (especially water melon) are among the worst offenders.
Other food intolerances (gluten) can cause fructose malabsorption but often, once you fix the first problem, fructose malabsorption disappears.
Final thought: are modern fruits too sweet for us to digest properly?
Sometimes if a population is away from a food source for a long time, and there is no natural selection towards a needed ability, then this ability can degrade or become lost. Just like fish in underground caverns eventually lose all their pigment and eyesight over the generations. Things are not conserved if they are not needed. It could be that some populations did not have access to much fructose and so their ability to process and tolerate it has degraded. However, since there is a specific metabolic pathway in the average human that is specifically set up to handle fructose, I do not think it likely that humans in generally were generally designed not to eat any at all. I do think were were designed to eat much much less than currently eat on the average SAD. And I also would not be surprised if people with all kinds of gut damage, blood sugar issues, and gut flora imbalances would have added problems with any kind of sugar or starch. However, I do think that for the big majority of humans, moderate intake of fructose such as would be obtained from moderate intake of whole fruits, if done from childhood such that metabolic damage never happened in the first place, would be perfectly fine. However, if I were native American, innuit, or one of the groups that might be less adapted to carb intake, I'd be extra careful.
Thoughts on fructose malabsorption on Evolutionary Psychiatry:
I am unable to eat most fruits as well. The only thing I allow myself is a little lime juice when I cook fish. I seem to do ok with that so far. It can be very limiting here on Paleo but possible. I just focus on meats and veggies, and I do use lactose free milk and butter. :) I have not tried to reintroduce other fruit and don't miss it. I never really liked it to start with. I do however wonder if this could be a reason I have low energy.
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