Food Intolerance: Fructan Intolerance, Can Enzymes Help? 


By Leyla Moudden, Naturopath

Fructans are beneficial carbohydrates with potent antioxidant effects that feed the beneficial gut bacteria that line the large intestine and colon. Fructans are carbohydrates found abundantly in many health-promoting foods such as grains, wheat, fruits, legumes, and vegetables.  

Fructans are oligosaccharides and stand for the “o” in FODMAP. They have been identified as a trigger for the gastrointestinal symptoms associated with irritable bowel syndrome: bloating, flatulence, abdominal pain, heartburn, belching, and bowel spasms. The therapeutic response to fructan induced IBS to date is the total avoidance of fructans or a FODMAP diet.

Intolerance reactions to fructan are identified via an elimination diet, a hydrogen breath test, or self-reporting by the patient. The FODMAP diet has been extensively studied and confirmed as a successful intervention for relieving IBS symptoms. However, the problem is that the majority of FODMAP foods, and particularly fructans, are important prebiotic foods that confer valuable health benefits. Lifelong avoidance of fructan is detrimental to overall health. Is there a better way of managing fructan intolerance?

Fructans – Important Oligosaccharides 

Fructan is a storage carbohydrate found in approximately 15% of flowering plants. The majority of fructan digestion occurs in the large bowel. During digestion, fructan provides an important carbon source to beneficial bacteria such as bifido and lactobacilli species. Studies on fructans show a strong correlation between fructan ingestion and improved lipid metabolism, reduction of LPS, and diacylglycerides. [1] 

Fructans have also been linked to a reduction in gastrointestinal infections as they selectively grow lactic-acid producing bacteria, reducing intestinal pH. Bowel habits and function tend to be improved, particularly in instances of constipation. Colonic absorption of calcium and magnesium, colon cancer-protective effects, increased beneficial bacteria, relief from constipation, and minimisation of gut permeability are just a few of the clinically observed beneficial effects of fructans. Inadequate consumption of inulin rich fructans may contribute to liver and intestinal inflammation and the development of non-alcoholic fatty liver disease. [2],[3]

In a 2019 single group design trial, 26 healthy individuals received a high inulin-type fructan diet. After three weeks, satiety improved, beneficial bacteria increased, and harmful bacteria reduced. The only negative observation was increased flatulence.[4] 

In a 2019 pilot trial on patients with Ulcerative Colitis, 31 randomly selected patients were given inulin-type β-fructan supplementation for three weeks at different dosages. At the end of the trial, patients in the high dose fructan group entered clinical remission. In the low dose group, there was a significant reduction in inflammation. A greater abundance of beneficial bacteria occurred in both groups. Flatulence was the primary adverse side effect in both groups.[5] 

Intolerance Reactions To Fructan 

Hereditary defects in enzymes required for effective fructan digestion exist but are rare. Fructans are fibres. Minor hydrolysis of fructan occurs in the stomach; however, the human gut lacks the enzymes needed to digest β-linkages.[6] Fructans reach the colon in small complete osmotic molecules that draw in water and lead to diarrhoea. In the colon, they are fermented by gut bacteria, producing H2, CH4, and other gases, sometimes generating discomfort.[7] These adverse effects are dose-dependent, with 10-20 grams of fructan being the suspected threshold at which IBS and intolerance reactions are likely to occur.[8]   

The Role Of Digestive Enzymes 

A digestive enzyme called α-galactosidase has reduced the adverse side effects of poor fructan digestion in clinical trials. In clinical trials, the abdominal pain and discomfort associated with fructan consumption in sensitive individuals have reduced in severity with α-galactosidase supplementation.[9] 

In a 2007 randomised, double-blind placebo-controlled trial, eight healthy volunteers were fed high fructan food and supplementary α-galactosidase or placebo. Bowel symptoms, flatulence, and hydrogen breath tests were measured. The α-galactosidase group showed a statistically significant reduction in problem digestive responses compared to placebo.

In 2013 a single centre, randomised, double-blind, placebo-controlled, parallel-group study was conducted in a paediatric tertiary care setting. Fifty-two female patients aged between 4 and 17 with gastrointestinal disturbance were given α-galactosidase at bodyweight dosage for two weeks. The digestive enzyme significantly reduced global distress compared to the placebo.[10],[11]

In a 2018 randomised, double-blind, placebo-controlled, cross-over trial 31 patients who met the Rome III criteria for IBS were fed a high fructan diet alongside α-galactosidase supplementation. Of the patients who experienced adverse effects on ingesting fructan, supplementation with α-galactosidase significantly reduced IBS symptoms.[12] 

Enzymes As A Supportive Therapy 

Fructan consumption is associated with increased satiety, reduced food cravings, diverse beneficial gut bacteria, improved blood glucose regulation, immunomodulation, and cardioprotection.

Removal of dietary fructans, particularly within the context of a FODMAP diet will temporarily reduce IBS like food intolerance symptoms and significantly reduce beneficial gut bacteria, specifically bacteria responsible for butyrate production and mucus reduction.  

Excessive dietary restriction can also lead to disordered eating and orthorexia, and eventually anxiety, depression, fatigue, and nutrient deficiency.[13]

Oral supplementation with α-galactosidase can provide a significant reduction in food intolerance reactions. Combined with enzymes that address other FODMAP groups, oral enzyme supplementation can form an adjunctive therapy to a FODMAP or elimination diet. Depending on the severity of the symptoms and the volume of fructan consumed, enzyme supplementation may be enough to alleviate or reduce intolerance symptoms. Enzyme supplementation can also be used in the re-introduction phase of elimination diets to facilitate greater dietary freedom and variety for the patient’s benefit and as an adjunct therapy to an elimination diet.  

Enzyme Science Intolerance ComplexTM

Intolerance Complex by Enzyme Science contains α-galactosidase to facilitate better hydrolysis of fructan. As food intolerant individuals will frequently have an intolerance reaction to more than one food group, the intolerance complex also contains enzymes to facilitate the more effective breakdown of gluten, casein, lactose, complex carbohydrates and phenols. 

All Enzyme Science products are ethically produced and selected for their effectiveness throughout the digestive tract.  


[1] Althubiani, A., Al-Ghamdi, S., Samreen, Qais, F., Khan, M., Ahmad, I. and Malak, H., 2019. Plant-Derived Prebiotics and Its Health Benefits. New Look to Phytomedicine, [online] pp.63-88. Available at: <> [Accessed 14 December 2020].

 [2] Man, S., Liu, T., Yao, Y., Lu, Y., Ma, L. and Lu, F., 2020. Friend or foe? The roles of inulin-type fructans. Carbohydrate Polymers, [online] 252, p.117155. Available at: <> [Accessed 14 December 2020].

[3] Man, S., Liu, T., Yao, Y., Lu, Y., Ma, L. and Lu, F., 2020. Friend or foe? The roles of inulin-type fructans. Carbohydrate Polymers, [online] 252, p.117155. Available at: <> [Accessed 14 December 2020].

[4] Hiel, S., Bindels, L., Pachikian, B., Kalala, G., Broers, V., Zamariola, G., Chang, B., Kambashi, B., Rodriguez, J., Cani, P., Neyrinck, A., Thissen, J., Luminet, O., Bindelle, J. and Delzenne, N., 2019. Effects of a diet based on inulin-rich vegetables on gut health and nutritional behavior in healthy humans. The American Journal of Clinical Nutrition, [online] 109(6), pp.1683-1695. Available at: <> [Accessed 14 December 2020].

[5] Valcheva, R., Koleva, P., Martínez, I., Walter, J., Gänzle, M. and Dieleman, L., 2018. Inulin-type fructans improve active ulcerative colitis associated with microbiota changes and increased short-chain fatty acids levels. Gut Microbes, [online] 10(3), pp.334-357. Available at: <> [Accessed 14 December 2020].

[6] Franco-Robles, E. and López, M., 2015. Implication of Fructans in Health: Immunomodulatory and Antioxidant Mechanisms. The Scientific World Journal, [online] 2015, pp.1-15. Available at: <> [Accessed 14 December 2020].

[7] Donahoe, R., Attaluri, A., Schneider, M., Valestin, J. and Rao, S., 2010. W1370 Absorptive Capacity of Fructans in Healthy Humans: A Dose Response Study. Gastroenterology, [online] 138(5), p.S-709. Available at: <> [Accessed 14 December 2020].

[8] Cox, T., 1994. Aldolase B and fructose intolerance. The FASEB Journal, [online] 8(1), pp.62-71. Available at: <> [Accessed 14 December 2020].

[9]Di Stefano, M., Miceli, E., Gotti, S., Missanelli, A., Mazzocchi, S. and Corazza, G., 2006. The Effect of Oral α-Galactosidase on Intestinal Gas Production and Gas-Related Symptoms. Digestive Diseases and Sciences, [online] 52(1), pp.78-83. Available at: <> [Accessed 14 December 2020].

[10] Di Nardo, G., Oliva, S., Ferrari, F., Mallardo, S., Barbara, G., Cremon, C., Aloi, M. and Cucchiara, S., 2013. Efficacy and tolerability of α-galactosidase in treating gas-related symptoms in children: a randomized, double-blind, placebo controlled trial. BMC Gastroenterology, [online] 13(1). Available at: <> [Accessed 14 December 2020].

[11] Tuck, C., Taylor, K., Barrett, J., Gibson, P. and Muir, J., 2017. Oral α -galactosidase improves gastrointestinal tolerance to a diet high in prebiotic fibre (galacto-oligosaccharides). Journal of Nutrition & Intermediary Metabolism, [online] 8, p.71. Available at: <> [Accessed 14 December 2020].

[12] Tuck, C., Taylor, K., Gibson, P., Barrett, J. and Muir, J., 2018. Increasing Symptoms in Irritable Bowel Symptoms With Ingestion of Galacto-Oligosaccharides Are Mitigated by α-Galactosidase Treatment. American Journal of Gastroenterology, [online] 113(1), pp.124-134. Available at: <> [Accessed 14 December 2020].

[13] Hill P, Muir JG, Gibson PR. Controversies and Recent Developments of the Low-FODMAP Diet. Gastroenterol Hepatol (N Y). 2017 Jan;13(1):36-45. PMID: 28420945; PMCID: PMC5390324.

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