Another reason to avoid eating too much fructose

One of the emerging themes in nutrition over the last decade has been just how toxic the sugar fructose can be to the body. This sugar, originally touted as ‘healthy’ as a result of the fact that it was found in fruit and did not raise blood sugar levels in the short term, has been linked with a variety of health issues including obesity, metabolic syndrome, ‘fatty’ live and type 2 diabetes. See here for a one and a half hour lecture by American doctor and research Dr Robert Lustig on some of the reasons we really do need to be wary of consuming too much fructose.

Dr Lustig and his team have recently produced another piece of research focusing on fructose, and specifically its potential role in abdominal symptoms of unknown origin. Some individuals, including children, can have symptoms such as bloating and abdominal pain for reasons that are not, in a conventional sense, altogether clear. Sometimes, these individuals end up with a ‘diagnosis’ of irritable bowel syndrome (IBS). IBS is not really a diagnosis at all – it basically is we doctors way of saying “you have abdominal symptoms but we do not know why.”

In my experience in practice, IBS is very often the result of food sensitivity issues (especially wheat) and/or some sort of imbalance in the organisms within the gut (sometimes referred to as ‘gut dysbiosis’). However, according to Dr Lustig’s recent research, presented at American College of Gastroenterology annual scientific meeting in Texas, US, another important cause of abdominal symptoms, at least in children, is fructose.

In this study, which you can read about here,  245 children and adolescents aged 2 – 18 with chronic abdominal pain (perhaps associated with other symptoms such as constipation and/or diarrhoea, wind and bloating) were tested for ‘fructose malabsorption’ (an inability to absorb fructose) with something known as the ‘breath hydrogen test’. In this test, individuals are given fructose, and then levels of hydrogen are measured in the breath. And increase in hydrogen levels in response to ingestion of fructose marks some out as a fructose ‘malabsorber’.

In this study, about 54 per cent of individuals were found to fructose malabsorbers. Those identified as such were then put on a low-fructose diet. The result? About two-thirds of these individuals experienced a resolution of their symptoms.

This study suggests that fructose malabsorption is common in children with unexplained abdominal symptoms, and the fructose reduction can control symptoms in many of these children. One of the reasons that this diet may not have been as successful as it might be is because some children may not have adhered to the low-fructose advice. Also, it’s possible that some of the children have other things going on (e.g. another food sensitivity or gut dysbiosis) that might need remedying for there to be symptom resolution.

To my mind though, this study gives us yet another potential reason to be careful about how much fructose we consume. It’s also going cause me to consider fructose malabsorption in patients who have chronic (long-term), unexplained gut symptoms.

8 Responses to Another reason to avoid eating too much fructose

  1. Bill 21 October 2010 at 4:18 pm #

    Dr. Briffa,
    What’s your views on occasional bouts of wind? I eat a paleo type diet with intermittent fasting, and I believe my gut flora is in good nick.
    Number 4 on the Bristol Stool Chart is my norm.
    I do get wind sometimes after a meal with rare mild discomfort.
    Alleviated by a brisk (tuneful) walk. 🙂
    Is a certain degree of flatulence healthy?

  2. Reijo Laatikainen 22 October 2010 at 9:40 am #

    Fructose is a key player here, but it can be more than that. A recent review paper by Peter Gibson and Susan Shepherd (2010) concluded that 75 % of IBS patients may achieve significant relief by decreasing FODMAPs (short chain carbohydrates) in diet.

    FODMAPs (Fermentable Oligo-, Di-, and Mono-saccharides, And Polyols) are fermented by bacteria only in colon, resulting in excessive gas producton (and thus other symtoms) among those who are intolerant. If you’re interested, I’ve just reviewed a randomized study by Ong et al. on the effects of FODMAPs in IBS .

    In addition, Italian researchers have shown that 20 % of IBS patients are allergic to wheat’s and cow milk’s protein. (Carroccio A Clin Gastroenterol Hepatol 2009)

    What confuses me is, why we dietitians and gastroenterologists aren’t more proactive in advocating these advice. Afterall, IBS is very common and worsens quality of life severely.

  3. Deborah Booth 22 October 2010 at 6:41 pm #

    excuse my ignorance here, but I thought fructose was found in fruit – (we eat a couple of pieces each a day, loads of tomatoes, a fruit, (we live in Spain!) and lots of veg and lowish carbs) are you saying cut out fruit too??? Not really possible in this Garden of Eden in Galicia… so where on earth is all this fructose supposed to be?

  4. frances 22 October 2010 at 10:45 pm #

    does this mean that fruit is out or are there some fruits/veg that are better than others? Is there an easy way of seeing the fructose content of various fruit and veg? FD

  5. Justmeint 23 October 2010 at 12:27 am #

    from what I read…. we need to be more paleo in our approach. Not over consuming fruits and vegetables that would not normally be available (seasonal) except they are available because they have been freighted in from elsewhere on the planet. Stick to local and truly seasonal fruits and vegetables. As an example the eskimo would not have banana or grapes normally available in any season…. Here in Tasmania mango is not a local fruit except it is freighted in from up north. Our Gut is suceptible to many issues, and is a very important part of our entire bodies – trest it with respect, and only eat what it was meant to eat, for our genetics.

    I follow (by necessity) the RPAH (Sydney) Failsafe Diet as I have multiple food chemical sensitivities……. no modern grains, wheat, barley, oats, rye etc, no casein and very low salicylates and amines. I am low fructose too….. it does make a vast difference to body problems.

  6. Karen 23 October 2010 at 7:12 am #

    Great post! I have fructose malabsorption and it is a real pain, I try to eat paleo but find myself limited as I also react to amines at the moment, but hopefully not forever.
    There are loads of options for people wanting to reduce their fructose intake, I still manage to eat some fruit, along with vegies at each meal. Just some mental gymnastics when you first start.

  7. Terry Smith 21 January 2011 at 7:33 am #

    My thought is that natural Fructose in fruit cannot be harmful. It is ‘the manmade high fructose corn syrup” that is the cuprit. I read many years ago that ‘high fructose corn syrup’ was not digested like sugar but went straight to the liver and was metabolized like fat. The article stated that they wanted to study to see if that was a reason for the weight gain of Americans in the early 1970s. I stopped drinking gin and tonics because there was not a soft drink out there that did not contain it except the diet drinks which I avoid. A retired nurse.


  1. Fructose in the firing line again… | Dr Briffa's Blog - 29 October 2010

    […] Last week, one of my blogs explored the potential for the sugar fructose to provoke unwanted bowel symptoms including abdominal discomfort and bloating. I mentioned, albeit in passing, that there were likely other reasons to be somewhat wary of fructose. It has, for instance, been implicated as a potentially potent cause of weight gain and type 2 diabetes. For the original post, see here. […]

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