Dietary Supplements for Irritable Bowel Syndrome

January 6, 2022 , ,

Irritable bowel syndrome (IBS) is the most common gastrointestinal disease in the world, affecting about one in seven people and is more predominantly found in women. The causes of IBS are still unknown. It is a multifactorial disorder involving an interaction between the digestive system, intestinal bacteria, the nervous system, and external factors such as stress. IBS can begin during childhood, adolescence, or adulthood and can disappear unexpectedly for certain periods during a person’s life and reappear at any age.

Several methods have been shown to be effective in reducing IBS symptoms, including practicing a relaxation activity, a low-FODMAP diet*, and taking certain medications. Some dietary supplements have also been  studied in connection with IBS. Here are the main supplements whose effects on IBS symptoms have been the subject of clinical studies. Please note that this article does not provide any recommendations for any supplement. The best person to determine your supplement needs is a registered dietitian, doctor, or pharmacist, who can provide you with individualized advice according to your situation.

Peppermint oil

The main active ingredient in peppermint oil is l-menthol. It may exert antispasmodic, antimicrobial, anti-inflammatory, and antioxidant effects. For more information, read this article.

STW-5 (Iberogast)

Iberogast is a mixture of several medicinal plants that can act by exerting antispasmodic effects as well as effects on gut sensitivity. Several clinical studies have looked at the effects of this supplement in people with IBS and indicate that it may be effective in reducing stomach pain as well as the severity of general symptoms associated with IBS. It should be noted that this supplement may interfere with certain medications (e.g. Acetaminophen, Diazepam, Codeine) and that rare cases of toxicity have been reported following its consumption.


Melatonin is a neurohormone released by the pineal gland as a function of the circadian rhythm.  It is structurally similar to serotonin and can promote sleep. The concentration of melatonin in gastrointestinal tissues is ten to a hundred times higher than in the blood, suggesting that it may play an important role in the digestive system. Melatonin has analgesic and regulatory effects on intestinal motility (speed of digestion), which could help relieve abdominal pain and the feeling of abdominal distention (bloating), as well as improve the frequency of bowel movements in people with IBS. Melatonin may also benefit IBS by helping to regulate mood and stress. Thus, melatonin could target both the psychological components of IBS (stress, anxiety, depression and sleep disorders) and peripheral elements (abnormal bowel sensations and motility disorders).

A few clinical studies have been conducted to evaluate the effects of a melatonin supplement on IBS. These studies included a small number of patients (18 to 60 adults with IBS) who took a melatonin supplement (3 to 5 mg) at bedtime for a short period of time (two weeks to six months). Overall, studies suggest that melatonin may help reduce pain in IBS patients, but its effects on other IBS symptoms are unclear and more studies are needed. Melatonin supplements are relatively safe and inexpensive.


Glutamine is a non-essential amino acid, meaning that it is produced by the body as needed. It has been suggested that glutamine may help improve intestinal permeability, i.e. optimise the control of materials that are absorbed by the intestine to prevent the entry of unwanted substances into the bloodstream that can cause inflammation.

A two-month clinical study evaluated the efficacy and safety of taking a glutamine supplement (a 5g dose, three times daily) in 106 patients who had developed post-infectious (developed as a result of food poisoning) IBS with diarrhea (IBS-D) with increased intestinal permeability. Taking glutamine reduced symptom severity and daily stool frequency, and improved stool consistency and intestinal permeability when compared to a placebo. No serious adverse effects were observed. Further clinical studies are needed to validate these results.

It should be noted that glutamine supplements are expensive and the daily doses suggested on product labels are often lower than the doses used in clinical studies. A weaker dose will probably not be enough to provide beneficial effects. In addition, glutamine is widely available in protein-rich foods (meat, poultry, fish, eggs, tofu, etc.). Once absorbed, there is no guarantee that it will perform its functions in the intestine, since the body will use it where it needs it.


Probiotics are live bacteria or yeasts that, when ingested in sufficient quantities, can exert beneficial effects on health. Several clinical studies indicate that certain strains of probiotics may help relieve IBS-related symptoms. However, there are many different strains of probiotics. It is important to know that each strain of probiotics has effects that are specific to it. Indeed, each strain has a genus, a species, and a designation. The beneficial effects of a probiotic strain can only be attributed to the strains tested, and not to the species or the entire group of bacteria. In addition, to be effective, probiotics must arrive alive in the colon and in sufficient numbers. They must therefore not be degraded following their passage through the stomach and must be able to resist gastric acidity and pancreatic juices. Several factors such as storing temperature and the presence of food additives can also affect the growth and survival of probiotics. It is therefore important to choose a probiotic supplement that has been shown to be effective for IBS through clinical studies. In Canada, for adults, the products Align, Bio K+ IBS Control, Genestra Brands HMF IBS Relief and UltraFlora Intensive Care are among the leading probiotic supplements whereby their efficacy on IBS is supported by at least one good quality controlled clinical trial.


Prebiotics are a type of dietary fiber that is beneficial to the microbiota and gastrointestinal health by selectively supporting the growth of good bacteria. It should be noted that not all fibers are prebiotics. Prebiotics are found in many foods. To know the main food sources of prebiotics, read this article. Different prebiotic fiber supplements are available on the market and can be effective in improving stool consistency and optimising digestive health in people with IBS, for both constipation and diarrhea. The main types of prebiotic fiber supplements recommended for IBS are psyllium, partially hydrolyzed guar gum (PHGG), methylcellulose, acacia fiber, wheat dextrin, and polycarbophil calcium. The choice of supplement depends, among other things, on the type of symptoms (constipation, diarrhea or a mix of both) and the individual’s personal tolerance.

Digestive enzymes

Digestive enzymes are molecules responsible for breaking down food into smaller particles to promote the body’s absorption of the nutrients they contain. People with IBS may be limited in their ability to digest certain types of foods, including certain fermentable sugars, such as  FODMAPs. It is recommended to adopt a low-FODMAP diet for two to six weeks, followed by reintroduction trials, to identify which FODMAP families are poorly tolerated as well as their tolerance thresholds.  Subsequently, one may consider taking enzyme supplements specific to the families that they have trouble tolerating.

The enzyme supplements lactase (Lactaid), alpha-galactosidase (Beano) and xylose isomerase (Fructaid) help to facilitate the digestion of the FODMAP families lactose, GOS, and fructose respectively. Some enzyme supplements designed for IBS including Fodmate, Fodzyme and Intoleran products have recently appeared on the market. They contain different sets of the following enzymes: lactase, alpha-galactosidase, glucose isomerase, inulinase, pectinase, and polyol oxidases. The enzymes inulinase and polyol oxidases are new enzymes that are currently being studied to help with the digestion of fructans and polyols respectively. These products would aim to reduce digestive discomfort when consuming high FODMAP foods, but more studies are needed to demonstrate their effectiveness.


  • Shapiro, Deutsch and Chey (2020) An evidence-based narrative review of oral supplements for the treatment of patients with irritable bowel syndrome. Neuro Gastro Latam Rev; 4(1):33-46.
  • Sia, Wond and Ho (2014) Melatonin for the treatment of irritable bowel syndrome. World J Gastroenterol; 20(10): 2492–2498.
  • Zhou et al. (2019) Randomised placebo-controlled trial of dietary glutamine supplements for postinfectious irritable bowel syndrome. Gut;68(6):996-1002.
  • Skokovic-Sunjic (2021) Clinical Guide to Probiotic Products Available in Canada 2021 Edition.

*FODMAPs are fermentable carbohydrates that are partly responsible for causing symptoms in people with irritable bowel syndrome (IBS). For more info, read this article.


Kathryn Adel
Kathryn holds a Bachelor Degree in Nutrition as well as a Bachelor and a Master Degree in Kinesiology, all from Laval University. She is a Registered Dietitian and active member of the Ordre professionnel des Diététistes Nutritionnistes du Québec (ODNQ) and of the American Academy of Nutrition and Dietetics. She holds the Monash University's certification for the FODMAP diet and IBS, and has considerable clinical experience in that area. She is also an accomplished athlete, having ran track and cross-country at a national level. Kathryn specializes in sports nutrition, weight loss, diabetes, as well as heart and gastrointestinal health.

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