Saturday, August 7, 2010

Dietary Strategies for Fructose Malabsorption

After putting up yesterday's post about the strong link between depression and fructose malabsoprtion in women (and adolescents), my mind continued to spin for a while. And I woke up this morning with more questions. If you haven't read that post, you probably should before diving into this one, as it won't make nearly as much sense without the initial information.

First of all, the estrogen link. The study noted that none of the participants were on prescription medicines except oral contraceptives. Oral contraceptives have widely varying amounts of estrogen, but the study probably would have been too small to have detected a lot of difference. It makes one wonder. They also postulated that fructose malabsorption would make premenstrual dysphoria worse, again using the explanation that estrogen's effect on the liver makes the already low amount of tryptophan made into serotonin even lower. However, progesterone is the more likely culprit in premenstrual dysphoria, and depression is a well-known side effect of progesterone-only birth control methods. Look at the hormone levels in this diagram of the menstrual cycle - while estrogen is higher in the second half of the month, when premenstrual dysphoria is likely to occur, it really only spikes just before ovulation, in the middle of the month. Progesterone is quite low at the beginning, and then rises to steady levels for much of the last part of the cycle, until it drops again. Progesterone is also involved in the metabolism of serotonin and dopamine, so it could all be related.

Secondly - I had no idea that fructose malabsorption was so common. When I've seen notes or mentions of it around the internet, I had a mental note in my head - "rare" - and I must have been thinking of hereditary fructose intolerance, which can cause liver damage and is quite rare. Probably not much was known about fructose malabsorption when I was in medical school, or I would have remembered it. I mean, everyone knows about lactose intolerance, after all. But the fact that fructose malabsorption is so common could explain quite a bit about the increasing prevalence and changing symptoms of depression these days. Sure, the studies were small, but the effects of the carbohydrate malabsorption were quite large, which means that there's a good chance the data is meaningful. A lot of people (men and women) now have signs of "atypical" depression that is characterized by weight gain, fatigue, and prominent carbohydrate cravings. Low levels of serotonin are thought to trigger carbohydrate cravings, as carbohydrate is thought to increase serotonin levels in the brain. An unprecedented change in our Western diets has made high-fructose foods readily available year-round, something that was never possible before industrialization. So we have fructose-malabsorbers with depleted serotonin craving carbs, munching on sugary foods, leading to more cravings, and a vicious cycle ensues. Adolescents may be more vulnerable, as they are probably the most likely to have a free fructose-laden diet.

When I discussed the changes in depression symptoms from classical melancholia to the modern, atypical presentation, I had pointed the finger at the omega 6 fatty acids, which may also be involved. But fructose could be a very common factor - ironically, the fructose which is not absorbed is the problem! I wish I knew how common fructose malabsorption is in ethnic groups besides central Europeans. Forget straight-up zinc deficiency and the exorphins in wheat causing schizophrenia - those are relatively rare and cannot explain the recent huge changes and increases in depression and mental illness. But fructose malabsorption has the potential to be a huge factor for a good many people - if the 1/3 prevalence holds true for the American population, that's 100 million people. Even if it is much higher in those of central European descent, the fact that other ethnic groups have some of it still means millions and millions of people in the U.S. alone.

And now a bit more about fructose malabsorption, also from one of Jad's helpful references, "Fructose Malabsorption and Symptoms of Irritable Bowel Syndrome: Guidelines for Effective Dietary Management."

Fructose is found in three forms in the diet - as free fructose (in fruits, honey, high fructose corn syrup, agave nectar, etc.), as part of the disaccharide sucrose (glucose+fructose), and also as a polymer known as a fructan (found in wheat and some vegetables).

Turns out that the other constituents of our diets affect how well we can absorb fructose too. Glucose helps us absorb fructose, for example, as does the amino acid alanine. In moderate amounts, people with IBS symptoms and fructose malabsoprtion didn't get symptoms when they ate sucrose or balanced fructose/glucose mixes. But in immoderate amounts ("greater than 375 ml of sucrose-sweetened soda" was an example in the paper), even sucrose could cause symptoms.

So what exactly was the recommended diet (which was quite effective for the IBS symptoms, according to the study)?

Patients were advised to avoid the following foods which had an imbalance of fructose compared to glucose:

Apple, pear, guava, melon, mango, papaya, watermelon, star fruit
Anything with the following major sweetening ingredients: HFCS, corn syrup solids, fructose, and fruit juice concentrate

Also avoid the following foods which have a large fructose load (>3 grams per serving), balanced with sucrose or not:

Most dried fruits, especially apple, apricot, dates, raisins, pear, figs, and prunes
Fruit juice, canned packing juice
Fruit sauces (including tomato paste, chutney, relish, plum sauce, sweet and sour sauce, and BBQ sauce)
High sugar fruits (cherry, grapes, persimmon, lychee, apple, pear, watermelon
Coconut milk and cream (surely they mean sweetened coconut milk and cream - my can of 365 Coconut milk has only 2g of carbohydrate total per serving, and 1g of sugar)
Fortified wines such as sherry and port
> 375 ml of sucrose sweetened soft drink
"excessive intake" of confectionery.

For these items, the patients were advised to substitute apricots, nectarines, peaches, pluma, berries, citrus, ripe banana, and other fruits which have more glucose or equal glucose to fructose. They could also consume glucose powder or glucose-sweetened sports drink to balance out a fructose load. (In this paper, substitution was emphasized rather than avoidance of whole food groups, in order to prevent nutritional deficiencies or some such. One wouldn't want to do something scary like eat more fat in lieu of pasta, high-fructose fruits, and bread after all!).

Now the fructans - the most problematic ones (to be avoided) are:
White bread
Whole-grain breakfast cereal
crumpets (Australian study!)
jerusalem artichoke
onions (less of a fructan effect than the others)
asparagus (ditto for onions)
(I'm leaving out chicory root and some other rare foods - best you get the paper and see for yourself the complete list)

Again, the patients were encouraged to substitute - rye bread or gluten free bread, gluten-free pasta and rice and crackers, maple syrup, gluten-free cookies, etc. And after 2-40 months on the diet, 77% adhered to the diet most of the time, or frequently. 85% of the adherent folks had substantial improvement in IBS symptoms, whereas 36% of the nonadherers had improvement. As this was a dietary study for IBS sufferers with a positive test for fructose malabsorption, depression scales were not administered. It would have been nice if the researchers threw a couple in there, though, right?

Please check out Jamie's post on FODMAPS for even more information, and paleo-style avoidance of fructose and fructans.

Final food for thought - for most people, the vegetable fructans (jerusalem artichokes, onions, leeks, and asparagus) are thought to aid our health by feeding our bacteria a short-chain fatty acid, butyrate, which somehow decreases the permeability of the gut. One can also get butyrate from eating butter. (edited to say - sorry - meant the opposite - the fructans are transformed from the oligosaccharides to the short chain fatty acids by the good bugs. Thanks Avocado!)


  1. Regarding the final paragraph: The bacteria in the colon eat the undigested starches (fiber) and product short chain saturated fatty acids. Those SCFAs are absorbed and used for our metabolism. The bugs are feeding us the butyrate!

  2. I wonder how much of the improvement in the study at hand was placebo effect. I doubt all, but perhaps some...

    Some parents believe sugar makes their kids "hyperactive." The cut sugar consumption and report less hyperactivity. They see what they expect to see. But, if memory serves me well, that's not what the scientists saw.


  3. Hi Steve. I discuss that study you remember in my post on ADHD and food additives a while back. So for as this study, most of the participants had only one visit with a nutritionist explaining the diet, and then a follow up phone call. I thought the degree of adherence was remarkably high, suggesting to me a negative behavioral reinforcer - eating fructose = bloating and discomfort. That could have been a nocebo affect, I suppose. It was true the non-adherers had a 36% improvement, though.

  4. Thanks for the post (and the blog, you have written a lot of interesting content)!

    As an quite off-topic comment... Do you happen also to have some inteersting information about things called adrenal fatigue, stimulants/superstimuli, addictions, withdrawal? I'm just a layperson, but they at least seem quite important topics, as nutrition also is. And I would be interested to read your opinions.

    In case adrenal fatigue isn't a familiar term to you, there's at least some easy literature as Dr. Wilson's "Adrenal Fatigue: The 21th century stress syndrome" and Diana Schwarzbein's book "The Transition" also contains some information how many people are getting in trouble because of chronic stress due to dieting/excercising etc... Hmm :O

  5. Valtsu - I am planning on looking into adrenal fatigue! Thank you.

  6. I guess J Alfred Prufrock can eat his peach after all. He'll have to look elsewhere for the source of his melancholy and IBS. ;)

  7. so onions and asparagus have more fructose than glucose and would be bad for one with depression? did i read that right? i am checking out th paper now

  8. Hi Malpaz - asparagus and onions are fructans, which means chemically it has a fructose end that is cleaved off and becomes fructose, basically, in the gut. IF you have fructose malabsoprtion (you may not!) AND the link between depression and fructose malabsoprtion is real (the studies were small, but convincing to me - I sure would like to see some bigger studies, though!!), then it follows that avoiding fructose and the fructans would be a good idea. Jamie's FODMAPS post really explains some of the malabsoprtion part better than I did. Obviously, though, depression is multifactorial and fructose will not be the issue for most, if any.

  9. Just spoke with a friend of mine who is a gastroenterologist at a major academic medical center - yes, fructose malabsorption is rather newly recognized as an issue. She typically sees patients for IBS symptoms. She remembers a presentation on it with estimates of it affecting 15% of the population (I'm guessing a mixed American population?), but isn't sure on the citation for that one. They can do the hydrogen breath test (also test for CO2 and methane at the same time) after a fructose load (they do 100mg), but she has found that asking patients to cut out the soda and apple juice and tons of fruit for a couple of weeks can make the diagnosis for free - reduced gas and bloating - then if you are not convinced, try drinking apple juice after the break, and if cramping and diarrhea ensues, there you go. (Similar test for milk products and lactose intolerance). She wasn't aware of the depression connection until now. She said also that IBS is a "lumped together" diagnosis - that some is no doubt dietary, some is nerve or motility issues... she did not typically ask people to try giving up wheat also. She said the worst offenders were high fructose corn syrup soda and juices, and a lot of people tended to get better with cutting those.

    So, that's the current real world state of fructose malabsorption, at least at a major academic medical center in the Eastern U.S.

  10. Nice piece of info from your contact there Emily!

    Elimination-challenge diets are great for diagnostic purposes when they are done properly. They are time consuming though, and in the modern world we live in, there is an expectation that lab tests or those undertaken in a clinical setting are faster and more accurate. For example, most people will accept the results of a tTG for coeliac (and gluten, even though it doesn't actually test for gluten intolerance) as being better and more accurate than a gluten elimination/challenge. Likely because the tTG involves a doctor, a blood test, and the aformentioned doctor telling the patient that it is unlikely they are coeliac so can carry on eating bread!

    As I suggested in my winter blues post, I would encourage patients who suspect fructose malabsorption to also look for gluten as an underlying driver of that malabsorption. gluten driven enteropathy might be the silent factor in all of this. If it is damaging the GLUT5 transporters leading to fructose malabsorption, limiting fructose might see some symptom relief, but if the patient continues with gluten exposure, silent damage may still be occuring and potentially flare up as another issue at a later date.

    Of course, the easy thing to do would be to just go primal, then there is little to worry about then! :)

  11. BTW, with the current trends toward doing raw food juicing diets, does anyone know whether juicing large amounts of vegetable matter lead to greater levels of free fructose in the gut? I know many of these vegetables are low in fructose, but the shear volume some of these people are juicing (kilograms per day) may be increasing the loading.

    See video here for a recent media depiction of this. You will be rolling around in the floor when you watch the introduction and see the fitness model blame meat for her bloating and feeling lethargic... even though she eats low fat (and the fat she does get is mostly n-6, she still uses rice, and chews a mountain of chewing gum and artificially sweetened cola):

  12. Yes, Jamie I thought your notes on the GLUT5 transporter being damaged by gluten were very intriguing. Gluten intolerance/ fibromyalgia/ autoimmune stuff linked to gluten would take strict compliance to an elimination diet for several months to be sure of it - with lactose and fructose intolerance (at least the very obvious cases) you only need a couple weeks and a far less strict diet (putting aside the gluten and fructan issue) to figure it out. Given the state of health care (at least in the US) it does make sense to save some money and use the lab testing for the tough cases and research.

  13. I like your blog a lot- you are a lucid, clear, obviously well-informed writer. However after I leave your blog I see white letters burned on to my vision for almost a minute. Dark background/white lettered blogs are a bit of a pain. Just saying- I'll follow your very interesting blog anyway.

  14. I was waiting for the first complaint...

  15. More recent research is now available, than the article you site, at - oh and coconut milk and cream are only an issue due to high fat content so small amounts are OK (just depends on how much you count as small!). FODMAPs are more than fructans and fructose they also galactans and sugar polyols (see later research).

    With regards to the placebo effect, my bloating was so bad before diagnosis that when on the low FODMAP diet I lost half a shoe size. You cannot fake that.

    And a big thank you for bringing this topic up. It is something that is worth exploring as I know the gastrointestinal and psychological issues are more common than thought.

  16. Hi Carolyn, thanks for the link, as the Australian group is clearly the forerunner in this research. It really has the potential to be huge. I didn't focus on sugar polyols, but Jamie Scott mentions all of that in his FODMAP post at Primal Muse.

    "Placebo effect" is not really the same as "fake." There is considerable evidence it is mediated by opiates and is very, very real. I don't think the results in the study I covered could be explained by placebo effect, but it is always something one wants to keep in mind.

    Thanks so much for your comments!

  17. We wrote our own dietary guidelines They are in line with your post. We did not only focus on limiting fructose, but also on the avoidance of several other disease causing elements like for instance certain lectins and an abundance of omega 6. VBR Hans

  18. Hi Hans - I hope it is clear that I advocate (and follow myself) a primal/paleo style diet very similar to what you have in your link, though I do eat nightshades as the CSA box is full of tomatoes right now. The diet above was the research diet for that particular study. Since evolutionary medicine is in its infancy, the only paleo dietary trials have been for diabetes (and were small, but worked like gangbusters, not surprisingly).

  19. Fructose malabsorption is not a food allergy, meaning there is no production of IgE antibodies or release of histamine. There is also no typical allergic symptoms, like itching or hives.

  20. Hi, the link to Jad's post about paleo and fructose malabsorption does not work... does he still have a blog?

  21. I didn't know Jad had a blog - which link is broken?

  22. Im totally intrigued by your blog! I am a medical student in Michigan who has been fighting GI issues for 10+ years. I have tried everything - giving up lactose, giving up gluten, even having my gallbladder removed - to no avail. I first read about fructose intolerance about a week ago. I'm always skeptical because nothing has worked in the past, but figured cutting out fructose was worth a shot. I'm a week into it now and I feel amazing!!! My GI tract hasn't been this settled in YEARS. I'm noticing the mental effects as well - the "fuzzy head" is finally gone, even though I had no idea it was related to my food (I always blamed it on stress, lack of sleep, med school in general)

    I stumbled upon your page here while trying to learn more about it - both the physiology and how to prevent malnutrition, considering I haven't seen a doctor or dietician about it yet. Considering how many people in the US are probably affected, I am surprised at how few clinical trials are being conducted here on this topic, and how little information is available overall. Glad to see that it is picking up interest though.

  23. Hi - I enjoyed reading this a lot - I wanted to let you know the link to doesn't work - blogger says it's is "gone".


  24. Hi Chris - he moved to

  25. Dr. Deans, I'm just now reading this post of yours having recently been pointed in the direction of fructose malabsorption. Since December 2009 I have been on the GAPS Diet which eliminates some of the offenders but I have noticed over the last couple of years that when I eat too many carbohydrates for several days in a row I begin to feel depressed. I thought it was just carbohydrates, but now that I've been looking into FM, I am realizing it was not just carbs but more specifically fruit, honey and higher carb vegetables that can be problematic if one has FM (like carrots). Another side effect I have is that I have to be careful to not eat too high of carbohydrates with dinner or I will experience insomnia. The thing is, I don't have IBS. I do get gas when I eat artichokes and some of the foods that should be avoided. I can't really tell if my stomach is bloated - when I look down it looks like it is sticking out but in the mirror looking sideways it doesn't seem that bad. My question to you is can a person have FM and only have the depression? Four or five times over the last couple of years I have started to eat fruit/honey/higher carb veggies again and then after a few days realize I have become depressed and in a dark funk, and realize I've done it again, it's too many carbs. It takes 24 hours of abstaining and I begin to feel the depression lifting and day by day I feel better and better. But I always seem to start having fruit again, it seems quite innocent to me, it's like I somehow forget that I'm going to get depressed. So can someone with FM not have the IBS component, just depression? I am also treating adrenal fatigue and have hypothyroid symptoms so I know that can play a part but I seem to do pretty good and don't have depression until eating fruit/honey too many days in a row. Thanks for your thoughts.

    1. Just another voice chiming in that I too have no IBS (that I have noticed) when eating fructose, but DO have mood crashes/depression/anger problems. In my case, I had recently stopped taking Zoloft, and noticed pretty soon thereafter that my withdrawal symptoms: brain zaps and insomnia, were very bad after eating fructose. I thought that that might be just taking the Zoloft away, but now I wonder if I've always had fructose problems and the Zoloft had been the bandaid for it.

      If Starlene ever sees this, I'm curious as to if the GaPS diet has helped this or other symptoms, as I have just started it and it's annoying when I can't have half the already-limited diet.

  26. I am also looking for jamie post but no luck?

  27. I do not have IBS but I vomit when I eat most FODMAPS. I can eat dairy, though. It is in NO WAY a healthy diet to go to low FODMAPS. I can eat at most 1/2 cup of a fruit or vegetable per meal. And most fruits and veggies are not allowed at all. I can eat 1/4 cup of broccoli, no onion at all, no garlic, no cabbage. I can pretty much eat meat and white potatoes and white rice. It's worth it because I don't like throwing up all the time and I definitely have intense depression and anxiety, but it's not something I would recommend for anyone that doesn't have to be on it. Most of what I can't eat is healthy food. This diet absolutely does not fit in well with the paleo lifestyle. In fact, the healthier I ate, the worse my stomach hurts. White bread is not nearly as much of a problem as vegetables and fruit.

  28. Last week I noticed a connection between gluten and fructose malabsorption.

    I've been mostly gluten-free for years, although not strictly, as I'll eat a little gluten once every week or two.

    Last week I ate a smallish loaf of cinnamon bread and a tub of two-bite brownies over the course of two days. This higher dose of gluten seems to have kicked my low-level fructose malabsorption into high gear. I've had to give up all fruit for the past few days.

    So which is the problem-- wheat or fruit? or both?

    Since avoiding fruit 100%, I have been feeling much better in gut and in general; in the past, I've cut back but never eliminated fruit entirely. I love the taste of fruit though, so not sure what I'll do in future.

  29. Let me say as someone suffering from fructose malabsorption - this inability to process these foods is enough to cause depression. I do not believe it is the other way around. I have always, always been very active (running 5 - 10 miles per day), swimming, bike riding, parking far away for extra walking, eating a healthy diet and not denying myself sweets on ocassion. Until I began swelling to the point of 7 months pregnant and not being able to button my pants, headaches, nausea, and oh the pain. I was not on birth control, in my very early 30's, one child, and living a happy life. My diagnosis came after much testing (breath test and camera and several doctor visits) and pain.