Digestive Enzymes and IBS


Dr. Jane Varney - Research Dietitian, 28 April 2021

The Monash FODMAP Team have certified a number of enzyme supplements under the Monash University Low FODMAP Certification Program (for a complete list of Monash certified products, please refer to our app). These products are marketed to people who experience digestive discomfort after eating, including people with IBS, so we thought it timely to revisit the topic of enzyme supplementation in IBS.  

What are digestive enzymes?

Digestive enzymes are proteins that assist our bodies to breakdown and absorb the fats, proteins, and carbohydrates we consume from food. Examples are included in the table below:

Enzyme Produced By Role in Digestion
Amylase Salivary glands Breaks starch into glucose
Lactase Small intestine Breaks lactose into glucose and galactose
Protease Pancreas Breaks protein into peptides and amino acids

Digestive enzymes are naturally produced by the gastrointestinal tract, so in most people, supplementation is not necessary. However, if digestive enzyme production is insufficient (as it is in people suffering disorders such as cystic fibrosis and pancreatic insufficiency) enzyme supplementation is an essential therapy. 

What does the research say about digestive enzymes?

When it comes to enzyme supplementation in IBS, most research has looked at the effects of supplementation with lactase (the enzyme that digests lactose) and alpha-galactosidase (the enzyme that breaks down GOS). 

Do lactase supplements help people with IBS?

Let’s start with lactase. As highlighted in the table above, lactase is produced by cells lining the brush border of the small intestine and used to break lactose into glucose and galactose. These individual sugar units are both rapidly absorbed in the small intestine. However, when lactase production is limited, undigested lactose attracts water into the small intestine and passes undigested into the large intestine, where it is fermented by gut bacteria. This phenomenon is known as lactose malabsorption. Depending on the amount of lactose consumed and the sensitivity of the bowel, these effects can result in unpleasant symptoms such as diarrhoea, flatulence and bloating. People who experience these unpleasant symptoms are said to have lactose intolerance. 

Lactose intolerant individuals usually need a lactose restricted diet to manage their symptoms. Lactose is found predominantly in dairy foods such as cows’ milk and yoghurt, with lesser amounts found in soft cheeses, custard and cream, and minimal in butter, hard cheeses The diet is not lactose-free as most individuals can tolerate 12-15 g of lactose per day (equal to around 1 cup of milk), and possibly more if lactose intake is spread out over the day⁵⁴. The diet is also not ‘dairy-free’,  as many dairy products are very low in lactose (such as hard cheeses and butter), while richer sources of lactose (such as milk and yoghurt) are safe to consume in small serving sizes. Lactose free varieties of lactose rich dairy products are also widely commercially available (e.g. lactose free milk and yoghurt). Following the correct diet is important because dairy products are rich, natural sources of calcium, phosphorus and vitamin D, which are all essential for bone health. 

Lactase supplements are typically available in tablet or droplet form. The droplets are typically added directly to the dairy product (such as milk or yoghurt), where they break down the lactose prior to consumption. Alternatively, these supplements can be taken orally just prior to consuming a lactose rich dairy products. 

So do lactase supplements really work?

The answer is yes and no. Lactase supplements generally improve tolerance of lactose containing dairy products in lactose intolerant individuals¹²³. But symptoms of IBS generally cannot be managed with lactase supplements alone (or a lactose restricted diet for that matter)⁴. Instead, lactase supplements should be seen as an adjunct therapy to assist with IBS management, and used alongside other effective therapies, such as a low FODMAP diet, psychological therapies and medication. They are useful for lactose intolerant individuals who do not want to restrict their lactose intake and prefer to continue consuming lactose-rich dairy products. 

What about alpha-galactosidase?

Alpha-galactosidase is an enzyme that breaks galactooligosaccharide (GOS) into simple sugar units. Because all humans naturally lack this enzyme, GOS is universally malabsorbed. Malabsorbed GOS travels to the large intestine where it acts as an energy source for our gut bacteria. Gut bacteria ferment the GOS which leads to gas formation and the production of short-chain fatty acids. Both the fermentation itself and its by-products have been shown to benefit health, but in people with IBS, the additional gas formation can lead to IBS symptoms such as flatulence, bloating and abdominal discomfort⁵. 

To manage these symptoms, dietary intake of GOS (which is found in foods such as cashews, pistachios, green peas, black beans, baked beans and  soy milk (made from soy beans) is restricted. Dietary restriction of GOS is most effective when done in the context of a low FODMAP diet⁶. 

Does alpha-galactosidase supplementation reduce symptoms of IBS?

Our team conducted a study to answer this very question and the answer is that in GOS sensitive individuals with IBS, yes. The study involved 31 people with IBS following a diet that was low in all FODMAPs except GOS. Participants moved through a series of test periods when they took the alpha-galactosidase supplement at either full dose, half dose or a placebo. The study showed firstly that the addition of GOS to a low FODMAP diet induced symptoms in most but not all people with IBS - approximately 1/3rd of people were not sensitive to GOS in this study. They also showed that the full-dose enzyme treatment improved IBS symptoms in GOS-sensitive individuals. This effect was not evident with the half-dose or placebo treatment, suggesting that a sufficient dose of enzyme supplementation (300 GALU) is needed to achieve tolerance of GOS containing foods⁷.

So what are our recommendations regarding the use of lactase and alpha-galactosidase supplementation? 

These enzymes are most useful in people with IBS who have completed Steps 1 and 2 of the FODMAP diet and in doing so, established their sensitivities to lactose and/or GOS. They are useful in enabling people to follow a less restrictive diet long term, as the enzymes digest the FODMAPs they are sensitive to, and thus enable them to eat more GOS and/or lactose rich foods. This is desirable as lactose rich foods are also rich sources of nutrients that are essential for bone health, while GOS rich foods are loaded with prebiotic fibre which is important for gut health and plant-based protein which is particularly important for people following vegetarian and/or vegan diets. 

Keep in mind that these supplements are not a panacea. They will not work for everyone, and should only be seen as an adjunct to other IBS therapies such as the low FODMAP diet, psychological therapies and/or medication. 

And as always, consult your health professional before beginning enzyme supplementation. 

Are other enzymes helpful for managing IBS, such as xylose isomeras?

There is less research to support the utility of other digestive enzymes on the market. This is not to say they do not work, simply that we are not sure yet whether they work. Our best advice is to consult with your healthcare professional before starting any enzyme therapy to consider whether these products are right for you. If you choose to try another enzyme therapy, try one thing at a time and monitor symptoms. This will help you to determine whether your IBS symptoms improve in response to taking them.


1.        O'Connell S, et al. A novel acid-stable, acid-active beta-galactosidase potentially suited to the alleviation of lactose intolerance. Appl Microbiol Biotechnol 2010;86:517-24.

2.        Lin MY, et al. Comparative effects of exogenous lactase (beta-galactosidase) preparations on in vivo lactose digestion. Dig Dis Sci 1993;38:2022-7.

3.        Portincasa P, et al. Beneficial effects of oral tilactase on patients with hypolactasia. Eur J Clin Invest 2008;38:835-44.

4.        Vernia P, et al. Lactose malabsorption and irritable bowel syndrome. Effect of a long-term lactose-free diet. Ital J Gastroenterol 1995;27:117-21.

5.        Tuck CJ, et al. Fermentable oligosaccharides, disaccharides, monosaccharides and polyols: role in irritable bowel syndrome. Expert Rev Gastroenterol Hepatol 2014;8:819-34.

6.        Halmos EP, et al. A diet low in FODMAPs reduces symptoms of irritable bowel syndrome. Gastroenterology 2014;146:67-75 e5.

7.        Tuck CJ, et al. Increasing Symptoms in Irritable Bowel Symptoms With Ingestion of Galacto-Oligosaccharides Are Mitigated by [alpha]-Galactosidase Treatment. Am J Gastroenterol 2017.

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