By Marina Iacovou (PhD Candidate and Accredited Practising Dietitian)
In an earlier blog post this year (http://bit.ly/1WvWU5Y) we speculated that although early studies suggested adding glucose to fructose may improve tolerance, the strategy was not looking promising – instead all it was doing was adding more sugar to the overall diet. There was confusion around this strategy with individuals adding glucose to all FODMAPs, not just fructose, which is the only FODMAP that could benefit from glucose addition. Consuming glucose tablets became common practice for many people when eating onion and garlic, foods rich in fructans, not fructose, which scientifically will not improve symptoms.
We can now confidently tell you that adding glucose to foods to help with the absorption of FODMAPs, even fructose, does not work.
One of our PhD candidates, Caroline Tuck, has published work on this very topic. If you want to read the full publication, please click here.
A brief summary of the study and its findings:
- Patients with a positive fructose breath test (“fructose malabsorption”) and functional bowel disorders such as IBS, were recruited. Healthy participants were recruited as a reference/control group
- Participants were provided with 6 different sugar solutions (PART A) – some acted as control solutions (glucose only) and others were combinations of fructose and glucose, and fructans and glucose which were compared to fructose alone and fructan alone
- Additional studies (PART B) were undertaken. where glucose was added to whole foods high in excess fructose
- It was a series of two randomised controlled, double or single-blinded crossover trials – this means that the participants (and in part A the researchers) were not aware what solutions were being consumed and the solutions were given in a random order. As such the results are more reliable
- Overall, breath hydrogen scores and patient symptoms did not improve with the addition of glucose to fructose or fructan solutions, or to whole foods
- Breath hydrogen responses in healthy participants were similar to patients with functional bowel disorders – showing that “fructose malabsorption” is normal
- The results of the study, question the reliability of breath hydrogen tests in a clinical setting.
So we can conclude that: 1) breath hydrogen tests, particularly to fructose, are unreliable – this is consistent with a previous study we posted about http://bit.ly/2fSaVcn and 2) Overall, the strategy of adding glucose to drinks or foods to lessen the effects of dietary FODMAPs on functional gastrointestinal symptoms, has no evidence.
Some of you may have been doing this already – taking glucose tablets with high fructose foods. If you really feel it helps, you can continue, but remember these points:
- Your total sugar intake will increase significantly
- Your tolerance to FODMAPs, including fructose, can fluctuate over time, so maybe this strategy is working because your tolerance to fructose has improved and you can drop the glucose without significant symptoms
Tuck CJ, Ross LA, Gibson PR, Barrett JS, Muir JG. Adding glucose to food and solutions to enhance fructose absorption is not effective in preventing fructose-induced functional gastrointestinal symptoms: Randomised controlled trials in patients with fructose malabsorption. J Hum Nutr Diet. 2016.