Is FODMAP good for your gut health?

FODMAP: is it really good for your gut health?

FODMAP is a dietary approach to support gut health and a popular and well known choice. And for those suffering with common digestive symptoms like bloating, pain, cramping and diarrhoea, it can provide fantastic relief. It seems obvious that if it provides symptom relief then it must be good for your long-term gut health, but this is not true, as I’ll explain below.

What is FODMAP?

Is FODMAP good for your gut health

FODMAP stands for “fermentable oligosaccharides, disaccharides, monosaccharides and polyols”. These are sugars (short chain carbohydrates) found predominantly in plant foods that can pass through the digestive tract and fermented by bacteria, creating gas, bloating and possibly pain. The sugars also draw more water into the colon, increasing the risk of diarrhoea.

FODMAPs are mostly plant based carbohydrates, such as: 

  • Fruits like apples, plums and pears and honey that contain fructose;
  • A wide range of vegetables such as broccoli, cauliflower, beetroot, onion and garlic;
  • Common grain products, especially wheat and rye, pulses
  • Artificial sweeteners like sorbitol
  • And also milk products that contain lactose.

Why can some people consume these foods and not others?

Is FODMAP good for your gut health

One explanation why some people are unable to digest and absorb the carbohydrates in FODMAP foods may be due to a lack of specific digestive enzymes usually found in the small intestinal wall. And this may be caused by a damaged gut mucosal barrier.

A second explanation is regarding the make-up of the microbiome and understanding which bacteria are fermenting these carbohydrates causing the symptoms. Is it an overgrowth of pathogenic bacteria rather than, as previously thought, the beneficial bacteria?

Thirdly, where in the digestive tract is this fermentation and bloating occurring? Is it actually in the small intestines due to an overgrowth of opportunistic (pathogenic) bacteria in this area, referred to as SIBO? The small intestines are the site of digestion, so any bacteria hanging out here can easily grab the carbohydrates and ferment them as fuel for their survival.

Why is a FODMAP diet problematic for long-term gut health?

Is FODMAP good for your gut health

These FODMAP foods should not be problematic to us. They are mostly vegetables and fruit, which are fibre rich. They also act as prebiotics to the beneficial gut bacteria – this means they are a fuel to help them thrive and grow. The most important thing we can do is to keep feeding these beneficial bacteria, as this crowds out space for pathogenic bacteria to grow.

 A healthy microbiome is dependent on diversity and an abundance of plant food. yet 75% of all the food produced in the World comes from only 12 plant species!

We may be encouraged to consume “5 a day” of fruit and vegetables, but many experts believe (me included) that it should really be “10 a day”. And we should be consuming 40 different plant foods every week to optimise the gut ecosystem.

It is not surprising to learn that long-term intake of a low-FODMAP diet is known to adversely affect the intestinal microbiota composition:

In particular, one study has identified that consuming 50% less FODMAP foods led to a 6-fold decrease in an essential gut bacteria called Bifidobacteria.

As the numbers of beneficial bacteria decline, it creates space and an environment allowing pathogenic bacteria to grow.

In addition, when these carbohydrates are fermented by beneficial bacteria, they produce short chain fatty acids like butyrate. Butyrate provides fuel for other bacteria and is a fuel for the epithelial cells of the gut wall. It helps to provide a robust gut mucosal barrier, helping to protect against inflammation and intestinal permeability.

A chicken-and-egg situation

Is FODMAP good for your gut health

So what comes first- a lack of bacterial diversity or a pathogenic overgrowth? Is it due to a low fibre diet initially but to resolve the symptoms people are encouraged to follow- a low fibre diet?!

Long-term intake of a low fibre diet lacking in diversity is further depletion of beneficial bacteria and potential increase in pathogenic bacteria.

Solutions to consider

Is FODMAP good for your gut health

Don’t fall into the trap like some of my clients who have followed FODMAPS for years! It’s important to move off such a restricted diet after 4–6 weeks for the reasons explained above. 

Certain in-depth DNA based stool tests are an excellent way to understand what is happening in your gut. It can help to identify poor digestion, intestinal permeability, bacterial species that can be associated with SIBO, pathogen overgrowth and depletion of beneficial bacteria.  Armed with this information, protocols can be put in place to help bring the gut back into balance. Be aware though that the information provided by these tests varies widely. An experienced practitioner will have researched the best tests available.

If you follow a FODMAP diet with success (as it relieves symptoms), then start a reintroduction in a controlled manner. Start by introducing a very small quantity of one food. Record reactions if any. If no reaction, increase the portion size the next day. After a few days, move onto another food. In this way, you can start to identify your own trigger foods and tolerance levels. It takes time and patience, but by doing this you should be able to reintroduce some of the restricted foods. This will help to encourage gut diversity without triggering symptoms.

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Keep your eye out for more articles and Peyton Principles in the media.


Gut Health Nutritionist Caroline Peyton Principles
Caroline is a Professional Nutritionist, Naturopath based in Wiltshire.

A little more about me…

Providing expert, personalised, health advice utilising 10 years of nutritional therapy and naturopathy experience with a strong emphasis on digestion and gut health. Zoom or face to face Consultations.

I also develop and deliver well-being in the workplace workshops.

Helping people live happier, healthier more active lives.

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Caroline Peyton

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