Given, the restrictive nature of the low-FODMAP diet, the possibility of inadequate nutrient is a concern.

Most studies have only looked at the effects of a 4 or 6 week elimination phase of the diet. Indeed, it is the Monash recommendation: to undertake the fully restrictive phase of the diet for only a short period to assess if it works for the individual and then start re-introducing the different FODMAP groups to identify the individual’s personal triggers and broaden out the diet as much as possible.

However, many people do stay on the full elimination phase for longer, perhaps becuase they feel good, and the timing isn’t right to move onto the challenge phases.

A recently published study looked at the effectiveness and safety of a 12-week strict low FODMAP diet undertaken under the guidance of a dietitian.

The study was run by a team at the University of Bergen in Norway. It included people with both IBS-D (diarrhoea predominant IBS) and IBS-M (mixed diarrhoea and constipation IBS sub-type). The participants met with a dietitian every four weeks from the start of the study until week 12 to receive education. A total of 36 participants completed the study at week 12.

Data was collected on food and drink intake (based on a 3-day dietary record), routine blood samples, IBS symptoms (measured through the standard IBS Severity Scoring System (IBS-SSS)), and standard IBS-related Quality of Life questionaire (IBS-QoL) used in many IBS studies, both at the beginning and after the 12 weeks.

The researchers found no significant change in intake of macro-micronutrients  (carbohydrates, fat, protein and fibre) although it is worth noting that carbohydrates and fibre intake was below the recommended guidelines both at baseline and at week 12.

Similarly, there was no significant change in micronutrients before and after the 12 week. However, several micronutrients (riboflavin, folate, vitamin C, vitamin D, iron, calcium, magnesium, potassium, selenium, and iodine) were below the recommended amounts both before and after the 12 weeks of the study.

The blood test results were in the normal range at both time points.

The diet was effective in reducing IBS symptoms in the majority of participants. The average (median) IBS severity went from moderate (at the start) to mild (at week 12). Overall, 60% of the participants were in the mild category at the end of the study and 80% were categorised as ‘responders’ to the low-FODMAP diet based on a drop in the IBS severity score of 120 points or more.

An 80% response rate is at the higher end of the range found for shorter studies, but not significantly higher. Indicating that if the diet doesn’t work quickly, it likely won’t work at all. Indeed, in this study the effects on symptom severity generally occurred in the first 4 weeks and were then maintained.

Quality of life measures improved among most categories, except measures of food avoidance and social reaction, which is perhaps expected. Adhering to a strict food regime may limit social activities with friends.

Key takeaways:

The study confirms that the Low FODMAP diet is effective in reducing symptom for the majority of for people with IBS-D and IBS-M and that a positive effect is typically apparent with 4 weeks.

If you have IBS, it is probably worth checking in with a dietitian to check that you are getting all the nutrients you need. The typical Nordic diet is generally viewed as a healthy one, and yet on average the participants were low in 10 micronutrients even before they started on the diet. They also didn’t meet health guidelines for fibre intake. Check out our Best Ever Poop program for information on how to add fibre to your diet including our Superflora range.

Certainly, consulting with a dietitian as you work through the three stages of the Low FODMAP diet is likely to be helpful. Dietary inadequacies are possible, and a dietitian is more likely to help you counter this. Indeed, despite restrictions, when working with a dietitian, the elimination phase it isn’t more likely to be deficient than a standard diet.

We recommend finding a dietitian that has undertaken the Monash FODMAP training. These are listed on the Monash app. If you don’t have the app flick us an email at flora@noisyguts.net and we’ll let you know the details of one near you.

One way to reduce the costs of working with a dietitian is to see your GP first for a Chronic Disease Management plan. This will provide you with a rebate for up to 5 services a year. The Medicare rebate is around $58 a session, which is unlikely to cover the full cost, but will help.

Try to find activities other than eating out or at home as a way to interact with friends and find social isolation. A walk by the beach or around a park or a shared yoga class are my favourite options.

Reference:

Hillestad, E. M. R., Steinsvik, E. K., Teige, E. S., et al. (2024). Nutritional safety and status following a 12-week strict low FODMAP diet in patients with irritable bowel syndrome. Neurogastroenterology and motility, 36(7), e14814. https://doi.org/10.1111/nmo.14814

Blog written by: Noisy Guts co-founder Dr Mary Webberley. Mary has a background in biology, with two degrees from the University of Cambridge and post-doctoral research experience. She spent several years undertaking research into the diagnosis of IBS and IBD. She was the winner of the 2018 CSIRO Breakout Female Scientist Award.