How does food affect your mood?

That queasy feeling in your stomach when you are stressed is a classic example of how your gut is closely connected to your brain. The food you eat affects your gut, and your “gut feeling” influences your mood.

How your gut and brain are connected and how stress affects them both

Let’s take a closer look at a disorder called “Irritable bowel syndrome”, or IBS. Monash University, Australia describes IBS as “characterized by chronic, relapsing symptoms including lower abdominal pain and discomfort, bloating, wind, distension and altered bowel habit (ranging from diarrhoea to constipation) but with no abnormal pathology. One in seven adults suffer from IBS”.

Long considered a functional disorder, or something that is not caused by an infection, it is now established that IBS has a significant impact on quality of life of people suffering from it. IBS is now being linked to chronic stress and the gut-brain connection.

Clinical and experimental studies have shown that psychological stresses have a marked impact on intestinal sensitivity and stress acts on the microbiota-gut-brain axis and causes IBS symptoms to flare up. Chronic stress including psychological stress has been found to induce IBS in lab animals.

Gut-brain connection


FODMAPs are a class of short-chain carbohydrates (sugars). The name comes from

Fermentable – when gut bacteria ferment undigested carbohydrates to produce gases

Oligosaccharides – present in foods such as wheat, rye, onions, garlic and legumes/ pulses

Disaccharides – present in foods like milk, soft cheeses and yogurts

Monosaccharides – present in honey, apples, high fructose corn syrups etc.

And Polyols – also called sugar alcohols, present in some fruits and vegetables and which are used as sugar replacements such as malitol, sorbitols etc.

The fermentable carbohydrates in FODMAPs are only partially absorbed in the gut (the rest are fermented – or digested – by gut bacteria). These types of fermentable carbohydrates are restricted in a low-FODMAP diet.When microbiome (the microbes in the gut) digest the FODMAPs, gases are given off, which can then cause you to have the most common symptoms of IBS – gas, bloating, and discomfort. FODMAPs in the gut also draw in water, which can further exacerbate the symptoms causing pain, cramping, and diarrhea. People with IBS have a bacterial composition that promotes excessive fermentation of FODMAPs, making otherwise healthy foods such as garlic, onions, lentils and beans to trigger gastrointestinal distress.


Chronic stress alters gut microbiome

Studies with animal and human subjects have shown that chronic stress can alter gut microbiome through bacterial translocation and cause the bacterial species that ferment FODMAPs to multiply excessively and create an imbalance in the intestines, causing symptoms of IBS. For example, chronic stress can result in a decline in the population of bifidobacterial species in the gut, contributing to IBS.

IBS-GUTIrritable bowel syndrome

Fodmaps and the mood

A recent randomized, double blind study gave a group of people with IBS and another group of healthy volunteers a variety of foods containing fructans (foods like wheat, garlic, onion contain fructans) through a tube directly into their stomachs. The result was that consuming fructans increased feelings of anger in both groups – IBS patients and the control group but the feelings of sadness and anger was especially high in the IBS patient group. This effect was seen within 30 minutes of being given the infusion.

A case study involving an athlete was done to analyze the effects of a low-FODMAP dietary intervention on GI symptoms and perception of wellbeing following heightened physical stress (sports-induced), and the results showed improvement in both GI symptoms as well as perceptual wellbeing with the low-FODMAP diet.

Your gut microbiota (microbial population) also determines your mood. Several studies show that probiotics have a positive influence on symptoms of anxiety and mood in people suffering from IBS and the control group (healthy people). Eating fermented and cultured foods containing Lactobacillus and Bifidobacterial species and supplementing with probiotics could help improve symptoms of stress and anxiety, as well as symptoms of IBS.

How food affects your mood

What it means for you

If you have IBS, you might want to consider a low-FODMAP diet not only for the relief of IBS symptoms, but also for the beneficial effect it is likely to have on your mood and perception of overall wellbeing. Everyone is different, so you probably have a varying degree of intolerance to FODMAPs, and you might not be intolerant to all of them. The FODMAP protocol is a period of elimination followed by a careful reintroduction of FODMAPs under the guidance of a trained professional. The reintroduction is done to identify the FODMAPs that you react to and those that you can safely have. Maintaining low levels of the offending FODMAPs may bring significant improvements to the physical symptoms of your IBS, as well as benefit your mood and mental well-being. And, don’t forget to supplement with probiotics. Lots and lots of beneficial bacteria in your gut will help manage your symptoms better. 

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