If you suffer with IBS, the chances are you'll have heard of the low FODMAP diet.  Developed by researchers at Monash University in Australia, the low FODMAP diet involves avoiding specific types of carbohydrate that some people find difficult to digest and absorb.

Since these carbs are not getting absorbed, bacteria in the gut start to feed on them.  The undigested carbs also attract water, which all combine together to create bloating, gas, abdominal pain and other IBS type symptoms.

The NHS recommends the low-FODMAP diet for IBS because it’s had great results for a lot of people in reducing their symptoms.

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FODMAP is an anacronym that stands for four different types of fermentable carbs: fermentable oligo-saccharides; di-saccharides; mono-saccharides and polyols.  They are found in a wide range of foods in varying amounts. Some foods contain just one type, while others contain several.

Common foods to avoid on the low FODMAP diet are:

  • apples
  • cauliflower
  • onions and garlic
  • beans
  • pasta
  • bread
  • dried fruit
  • cashew nuts

Typically, you stay on a low FODMAP diet for between two and six weeks, depending on how quickly your gut settles.  Once your gut is happy and calm, each carbohydrate group can be reintroduced, one at a time, to discover what FODMAP groups you can eat freely, which ones you might need to enjoy in small servings, and if there remain any FODMAPs that you may need to limit to keep your gut calm.

If you work with a practitioner, they may recommend that you include specific nutrients or digestive enzymes during this time, to support your gut restoration process.

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It is important to remember that whilst the low-FODMAP diet can be very successful at addressing the symptoms of IBS, it does not help resolve the root cause.  Working with an experienced practitioner can help you to dig deeper and find out why FODMAPs were causing you trouble in the first place.

I recommend the low FODMAP diet regularly in my clinic.  But... whilst it gets results, my clients often report side effects of fatigue, low mood and brain fog.  They also tell me how difficult it can be in social situations when they are unable to enjoy what everyone else is eating.  I can attempt to explain some of the biochemistry behind these effects, but I have never been able to empathise because I'd never tried the diet.  I didn't know how it actually felt to be on this diet for any length of time.

Until last week, that is, when I rolled up my sleeves and committed to seven days on a strict low FODMAP diet!  Here's what happened...

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Feeling confident!  I was also feeling curious to experience first hand the common side effects that my clients report.  I've always felt that I have pretty great gut function, so I wasn't expecting my gut to feel any better than it usually does.  This week was all about the mental challenge for me (or so I thought...)

The first thing I did was download the Monash University FODMAP diet app.  It includes the largest available database of FODMAP content in food, using an easy traffic light system to show you what you can eat and what you should avoid.  The app proved invaluable over the course of the week to search specific foods that you might be uncertain about (for example, blueberries are allowed but blackberries are not).  It's also packed full of explanations, recipes and food guides.

My first mistake was to assume that all herbal tea was allowed.  Not so!  Chamomile tea is high FODMAP and off the list!  Lesson learnt: if you're going to do this properly, don't assume anything.  Check everything!

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Day 2

Felt tired and yawny today, especially in the afternoon.  It was difficult to concentrate on my work, I had a headache and my vision was a little disturbed.  So this is the fatigue setting in!

Humans are dual fuelled machines.  We turn carbs into glucose and we use fats to turn into ketones.  A low FODMAP diet will likely change the ratios of fats/carbs/protein that you eat.  Fatigue can be a temporary issue as you change these ratios and your body has to shift gears to be able to use foods for energy in a new way.

I ALWAYS tell my clients to stretch their boundaries and eat as wide and diverse a diet as they can, even within the confines of an elimination diet… well, turns out this is easier said than done.  I didn't have the energy or the particular motivation to create interesting low FODMAP meals - at times it felt like I was just rotating between bananas, eggs, chunks of sweet potato and oats!  This is not a good idea - our microbiomes need diversity, which is why the low FODMAP diet is only recommended as a short term invervention (6-8 weeks maximum).

Day 3

Today I felt that my system had adjusted to the lack of carbohydrates.  I even felt quite energetic.  Interestingly, although I didn't think I had any particular digestive issues, my gut did start to feel lovely and ‘empty’ and completely settled.

Had a pub lunch with a friend - I was looking forward to finding out how challenging this experience would be.  Having eaten so plainly for the last few days, everything on the menu seemed impossibly rich!  (it's amazing how quickly we adjust to a new way of eating).  I ordered a Greek salad (no dressing) and when it arrived I realised I had forgotten to request no onions.  Spent a while picking them all out!

Day 4

This morning my stomach looked flatter than it has in years!  My gut still felt perfectly settled and empty, but overall I felt somewhat lacking in nourishment.

Had a work lunch meeting and couldn't find one single thing on the menu that met the low FODMAP criteria.  Settled for rooibos tea.  Hungry!

It's worth noting here that low FODMAP is particularly challenging if, like me, you are vegetarian.  Protein from meat and fish does not contain carbohydrates so is naturally low FODMAP.

Gut extraordinarily calm and settled.

Day 5

I'm starting to miss mushrooms and legumes... food with some density to it.  My energy is better today but I am feeling as though this diet lacks substance.  It's a very simple way of eating; food is for nourishment rather than for enjoyment.  Which of course is the truth!

I'm still eating the same things over and over again... finding it really hard to get motivated to diversify.

It's important not to eat too much of one food, even if it is low FODMAP.  Serving sizes are a very important element of this diet; for example, 10 almonds are low FODMAP, but 20 would be high FODMAP.  What you are looking for is your unique tolerance level; the Monash app can be a game changer here.

Wondering if I should invest in a FODMAP friendly protein powder to boost my macronutrient intake (I didn't do this in the end, but I probably should have done.  I would recommend that vegetarians do so).

Day 6

An energetic day planned today, ending with friends over for dinner.  I was physically busy all day and didn't have time to plan a low FODMAP lunch so good old eggs and bananas came to the rescue again #facepalm.

In the evening, I cooked for my friends so it was easy to control the ingredients.  I made a stew for them and made a mini one for myself without any high FODMAP additions.  Had I gone to a friend's for dinner instead, it would have been trickier.  My personal feeling is that it's too much to ask others to cater to this restrictive diet.  Lesson learned... when you're on low FODMAP, do all the entertaining yourself!

Day 7

This evening I made an effort to put a lot of variety on my plate and I felt full for the first time in a week.  Weight loss has been noticeable... 5lbs in total, which for some may be an added bonus (like for me!) but not for others.

If you are already at your ideal weight, be aware that it's very easy to accidentally eat too few calories on this diet which can lead to unwanted weight loss.  Ensure adequte portion sizes.

In some ways I'm glad this week is over but in truth, I haven't really missed any particular food.  I've felt hungry pretty much all week but in return I've had a beautifully well behaved stomach.

But in the long run, the low FODMAP diet starves bacteria (that's how it works) so it's time for me to start the reintroduction phase and find out which carb groups, if any, are causing symptoms and get back to a full and diverse diet.  This process can take many weeks so it's a good idea to work with an experienced practitioner who can help guide you.

The low FODMAP diet does take planning and commitment.  Stress directly impacts gut function, so choose a time when everything else in your life is fairly settled and prioritise this experience.  During the first few weeks of dietary restrictions, give your body the rest that it needs.



Remember, the low FODMAP diet can provide symptom relief but it will not fix the root cause of your digestive issues.  It's like a sticking plaster - use it to temporarily calm your gut whilst you and your practitioner work on resolving underlying issues.

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About the Author

Julie Hypher is a BANT registered Naturopathic Nutritional Therapist and founder of Wildwood Nutrition, a dedicated nutritional therapy clinic in Hamble, Hampshire. She runs private clinics every Tuesday and Thursday.

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