Who has Heard of Fructose Malabsorption?

Due to the rise in diabetes in the USA, for decades there has been a big marketing push to get people to use zero-calorie and low-glycemic sweeteners. I previously posted about health issues I connected to a zero-calorie sweetener, and noted that I also did better on a low-carb diet. Now I’m going to explain the simple science behind why certain sweeteners, including no-cal-sweeteners and even natural low-glycemic sweeteners like agave and honey, or even just the natural sugars in wheat, apples, and onions can cause major health issues for some people.

I only learned about all of this in 2011 when a podiatrist mentioned a study that found a connection between gout and fructose. I started researching the topic, and the information I found surprised me.

It turns out that around 30% of the population of Western countries and Africa have a condition known as Fructose Malabsorption. Asia has lower numbers, but it’s still around 10%. That’s a lot of people with a condition most of us have probably never heard of.

The condition exists when people do not produce enough of the enzymes needed to breakdown all the fructose in our modern diet. Undigested sugars end up in the intestines altering the profile of bacteria. While our digestive system needs probiotics, an overgrowth of even the good biotics can cause problems. It leads to fermentation and the production of hydrogen, carbon dioxide, and methane gases, leading to all kinds of digestive problems, nausea, fatigue, brain fog, and even gout. Many people with irritable bowel disease may simply have fructose malabsorption.

While it is called fructose malabsorption, because fructose is the main sugar that is not broken down, the lack of enzymes also keeps other sugars from being broken down, including sugar alcohols (any sugar that end in -ol, like sorbitol) along with fructans, which are found in grains like wheat.

Fructose is broken down in the liver by enzymes, but even average people can only properly absorb 25-50g of fructose per sitting. People are considered to have fructose malabsorption when they can absorb less than 25g. To put that into perspective, a 12 oz can of cola has about 22g, an apple has 13g, a tablespoon of honey or agave has about 8g. Someone with fructose malabsorption may not be able to properly digest even a single serving of one of those ingredients.

The two main forms of sugar we consume are glucose and fructose. Glucose is the sugar in our blood. Table sugar is sucrose, and sucrose is half glucose and half fructose. Interestingly, normal corn syrup is mostly glucose, but high-fructose corn syrup (HFCS) is corn sugar that has been processed so it’s around half fructose. Fruit juices also contain large amounts of fructose, especially apple and grape juices. Onions contain lots of fructose. It’s obvious that our modern diet, full of processed sugars and fruits year round, not to mention boxed fruit juices, contains much more fructose than humans ever consumed in the past, so fructose malabsorbtion is more of an issue.

Know anyone with irritable bowel or other mysterious digestive issues and fatigue? Along with lactose intolerance and gluten intolerance, two generally recognized  digestive issues, people may also want to rule out fructose malabsorption.

From my research, it appears the study of fructose malabsorption was brought to the greater attention of scientists in Australia while doctors were trying to figure out why some people responded so well to a wheat free diet who were not genetically gluten-intolerant (Celiac). Turns out wheat contains Fructans, which is a form of fructose.

I originally went gluten-free on my own twenty years ago. Doing so put my diagnosed Crohns disease into total remission, and was declared a miracle by my doctor. I did this diet against the wishes of my gastrointerologist, who insisted diet did not play any role in Crohns. He told me to instead prepare to spend the rest of my life sickly and undergoing surgery after surgery. My digestion has been problematic, getting markedly worse over the past six years, but the more research and experimentation I do with dietary restrictions the better I feel. My current hypotheses, based on all this research, and realizing the number of connections I’ve found, is that it wasn’t cutting the gluten, but possibly cutting the fructans, that saved me from the miserable future this gastroenterologist predicted. This is conjecture, but founded on plenty of dietary experience and research.

Luckily, there is a diet outlined for people diagnosed with fructose malabsorption. It’s known as the FODMAPS diet. Look it up if you’re curious about the details.

Just last year a new gastroenterologist told me that he thought all his patients that claimed they did better on a gluten-free diet were only imagining that they felt better. Seems he was not only totally ignoring all the science that states that 1 out of every 133 people are genetically gluten intolerant, but also the stats that show a massively larger percentage of the population has some form of fructose malabsorption. Anyway, getting off wheat is probably the hardest part of the FODMAPS diet, and something I did long ago, so taking it a little further wasn’t all that difficult for me.

The FODMAPS diet is very close in many respects to the Primal Diet. That’s why I went on a mostly Primal diet last year. You primarily eat vegetables and meat. This removes most of the right foods, but not all. I was also careful about using coconut flour and coconut milk, which are popular with the Primal Diet, as they contain fructose. You also have to cut out a few other  foods from the Primal Diet, including onions, which was a big loss. Apples and other high-fructose fruits also must be removed. The diet automatically cuts out a lot the hard to digest food groups, like dairy, sugars, and grains. I started by eating too many nuts, as that allowed me to create baked goods using nut flours, which made the transition easier.

As I mentioned in a prior post, six weeks after going on the diet I had blood work done. My numbers were better than they’d been in ages. My triglycerides and cholesterol plummeted to excellent levels. My stamina when exercising increased. I started sleeping better. My blood pressure lowered. My uric acid stabilized at a lower level. Consuming TruVia and Inulin caused major problems for me, and they apparently require the same enzymes that breakdown fructose. Changing my diet, reducing carbs and sugar, cutting out Truvia and inulin, together corrected my digestive system and lifted bad cases of brain fog and fatigue.

While a case of mild food poisoning, which alone further lowers enzyme activity, interrupted my investigation into this, I did just test myself by first going on a no lactose and low fructose diet. When my digestion was acting normal I made a lemonade using 12g of pure fructose as the sweetener and drank it. Because the sugar has to pass through the digestive system, enter the intestines, and multiply the gut biotics, it took 24 hours for the reaction to run its full course. The effects lasted a few days and slowly returned to normal. Repeat.

So, my theory as of today is that I appear to be in the large group of people who genetically have enzyme production too low for our modern diet. This means poor fructose, fructan, sugar alcohol, and Inulin tolerance.

As for the gout connection I mentioned at the beginning of this post: A couple of years ago my gout was acting up badly, so I bought a uric acid monitor. Uric acid monitors are like those glucose monitors used by diabetics. You prick your finger and feed a drop of blood onto a device that gives you real-time measurements. I found that when my levels went above 9 I was at an increased risk for a gout attack. My levels sometimes went as high as 11. While on this diet, my levels stabilized around 8. I went on enzyme pills for a few weeks. Doing this brought my uric acid blood levels down to 5. Sadly, when I mentioned this the gastroenterologist I saw last year said that gout is not a digestive issue and dismissed my findings. I had a piece of gluten-free apple pie at a family dinner. That night I could feel the pain buildup in my foot. My blood pressure also became elevated. In the morning I tested my uric acid levels. It was at 10 for the first time in months. Apples are a very high fructose fruit. My recent bout of food poisoning, which totally wiped out my enzyme production, also raised my uric acid levels. Sorry, but I now totally believe the study that showed a link between gout and fructose malabsorption, and I have no doubt that gout is a digestive issue. I love the empowerment of science and technology.

If you ever try a low-carb diet and find you do better on it, this may be why. If you have any digestive problems, you may want to give the FODMAPS diet a try for a few weeks to see if it helps, and maybe do a fructose challenge (using the fructose sweetened lemonade I mentioned above) to prove it further. And even if you do not have fructose malabsorption, do keep in mind your body can only tolerate so much fructose in one sitting. Drinking a large carbonated beverage or fruit juice, with more sugar or diet sugar alcohols or onions or fruit, may just be way more than your body can handle even with normal enzyme levels.

More Articles on Fructose:
Two Common Sweeteners Have Different Effects On the Body, Study Suggests
Fructose Consumption Increases Risk Factors for Heart Disease: Study Suggests US Dietary Guideline for Upper Limit of Sugar Consumption Is Too High
This Is Your Brain On Sugar: Study Shows High-Fructose Diet Sabotages Learning, Memory
Fructose-Sweetened Drinks Increase Nonfasting Triglycerides In Obese Adults


  1. teresa

    I just learned about fructose malabsorption this summer (2012) and think it is the cause of several years of mild stomach upset and sleep problems (I’ve struggled with chronic fatigue for years). I’ve tried to limit my fruit intake, but drank 1/2 glass of fresh squeezed orange juice last weekend. The next day, I felt like I was coming down with the flu (light-headed, mild stomach upset, trouble sleeping), but it doesn’t feel that bad. My blood pressure also spiked (150/ 95), when it is normally low (124/75). I’m thinking that this “attack” is my body’s response to the intense fructose. It sounds like your story of eating the apple pie and getting high blood pressure and elevated gout levels. Would elevated blood pressure after a fructose meal be another sign of this condition?

    • Al Bogdan

      I’m not a doctor, but from what you are saying it might be worth investigating. My physicals would give me a clean bill of health, meaning my blood tests were within generally normal limits and I wasn’t diabetic, yet I was always feeling rotten and run down and found these reactions to certain sweeteners. Experimenting with food choice has been great for my health.

      I highly recommend starting with a physical from your doctor to verify your health is good and to get some baseline blood tests. If you decide to do short food group challenges, I’d be interested in finding out what you discover.

      As I mentioned, with sugar it seems to be a good idea to compare how you feel after consuming different forms of sweeteners: glucose versus fructose in this case. I used normal servings of pure forms of each sugar from a health food store just to be sure it was the sugar itself I was reacting to.

      As I understand it you can also get high blood pressure after sugar consumption due to insulin resistance, which is very normal as we age, but insulin resistance is a reaction to the sugar in your blood stream and should be triggered by glucose as well, not just fructose. My physicals and self testing was to prove that glucose was not causing the digestive issues and headaches. It wasn’t.. Avoiding too much fructose and sugar alcohols helps with the gut issues, but I also keep all sugars low to maintain better triglyceride levels and better control blood pressure. Two different issues both related to sugar consumption.

      Hope you discover what’s been up.

      • teresa

        Thanks for the advice. I made an appointment with my doctor about my high blood pressure.

  2. Kate

    Awesome information! Thanks for sharing your findings from your experience of fructose malabsorption! I had been struggling over the years with chronic fatigue (which got mis-diagosed as depression) and I finally realized food was the culprit. I did a lot of arm wrestling with food as I am intolerance dairy, wheat, sugar (cane & beet) plus a handful of other foods. (I’m eating the foods from te paleo/primal diet now.) I knew I was close to the end of the chronic fatigue but had an issue with what seemed to be an intolerance to fruits or it was insulin resistance. If I ate, let’s say, three apples for the day, the first two apple were ok but the last apple would cause me to “get knocked out”, which is due to low blood pressure and syncope. The problem seemed to be sugar but I couldn’t quit pin point what was happening. I remembered that several of my friends had success with the FODMAP diet and checked that out. I was eating apples (low sugar) and not eating bananas (high sugar). After reading about the fructose and fructans, I removed them from my diet. I ate bananas, oranged, and grapefruits while ditching the garlic, onions, and apples. Wow! That made a huge difference in my energy level! I started working on projects that had been put aside because I was so tired and sick. Things had changed to where I didn’t want to stop working on the projects at night–if I could have gotten by with it, it would have been outside at midnight mowing my lawn! Huge energy difference!

    I also had a similar experience with the medical establishment. I would get a diagnose but no treatment plan. I had IBS and internal inflammation but wasn’t given any information as to how to manage it or what the next step would be. Since all my blood work would come back within range and I wasn’t losing lots of weight, I wasn’t concerned having cancer. I used the internet a lot in reading posts like yours, googling tons of words to see what information was out on the internet, and being very experimental in trying tons of things to resolve the fatigue problem. It took me a while to figure out the food connection. You’re not the only one who has travelled this road!

    I glanced over your recipe page and am going to have to make the Banana Pancakes. I just love the Paleo diet! I have made some great dishes plus I don’t react to the foods. Thanks again for sharing your experiences!

  3. Ele

    your story is so like mine- love the FODMAP DIET – IT HAS SOLVED MY IBS ISSUES.

  4. ACurtis

    Am going to look into this. Already gluten free/then totally grain free, soy free, cow dairy free, then went Paleo and cut out sugars (except for raw honey, 100% maple syrup, coconut sugar, Stevia–you know, the “good” sugars that are better for people and should be okay for “normal” people to eat). I have casein allergy and gluten intolerance. Apparently, I might actually have an issue with sugar/sugar alcohols–I haven’t been able to figure out my high blood pressure, when I KNOW there is a natural way to cure it if I can just get to the underlying cause! I am going on a 21-day cleanse as of Nov 1 (gut/colon), which should help normalize me, and part of the cleanse is to go off all sugars. So if that’s a problem/issue for me, we’ll know soon enough! Dr Mercola wrote about fructose and high blood pressure; he stated the only 2 “sugars” that people who have issues with fructose are able to tolerate are Lo Han and pure dextrose. Have you tried them? How do you do on those? Or do you just not use any sweetener whatsoever? Was disappointed to hear about coconut flour; most of my baking uses almond flour, but there is still a bit of coconut flour in the recipes. Hmm. Very interesting.

    • Al Bogdan

      It’s a tolerance issue. Everyone’s tolerance levels will be different. Some people will be able to eat more of these sugars and some people can’t have any. I find I can tolerate some beet sugar, maple syrup, real Stevia (not Truvia),and coconut sugar without noticeable symptoms as long as I don’t eat too much of them too often. Once you get used to less sweetener you should find you don’t need as much for things to taste good anyway. I’ve found that if I’m eating clean my tolerance is higher for cheating during a single meal as long as I don’t keep eating the bad stuff multiple meals or days in a row. For example, I can drink a glass of apple cider on occasion, but if I drink multiple glasses or a glass a day it’s bad news. Same goes for eating different forms of difficult to absorb sugars, like having cider one day, something with sugar alcohols the next, and then something with lots of onions the next; this would be bad news.

      Dextrose is not a problem, and in fact I add dextrose to recipes that have some fructose. Dextrose is readily absorb-able and I it’s said that eating dextrose with fructose should help you absorb more of that fructose. I have not run any experiments to prove this to myself.

      Hope your diet experiment works out for you. I think the best technique is to go cold turkey and then after a few weeks of feeling good try some tolerance tests to see what you can handle.

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