Exploring the Differences Between FODMAPs & Food Chemicals

Exploring the Differences Between FODMAPs & Food Chemicals

Written by Frances Walker APD, The Food Intolerance Dietitian

Food chemical intolerance and FODMAP intolerance have one big overlap- they both can cause IBS symptoms.

If your IBS symptoms have not improved or only partially resolved on the low FODMAP diet, you may have other underlying food intolerances such as food chemicals. Being aware of potential IBS triggers increases the chances of better management of your IBS.

FODMAP intolerance is a sensitivity to the small carbohydrates in food that are poorly digested but are important nutrient sources for our gut microbes. Food chemical intolerance is a sensitivity to food chemicals that that occur naturally in food (salicylates, amines and glutamates) as well as some problem food additives. A number of commercial low FODMAP foods (especially if gluten free) contain these food additives.

FODMAPs are poorly digested so stay in the gut where they attract water into the gut and are rapidly devoured but our gut microbes producing gas. This leads to the symptoms of IBS. In contrast, food chemicals are absorbed across the gut wall and zip into the body where they can access the whole body and cause a range of symptoms. This provides some explanation for the difference in the type and variety of symptoms triggered by FODMAPs compared to food chemicals.


FODMAPs stay in the gut and only cause gut symptoms. Other food related symptoms often be reported such as skin rashes, sore tongue or nausea are not FODMAP symptoms.

FOOD CHEMICALs typically cause a variety of symptoms (5 - 6 on average) which can include IBS symptoms, although sometimes just one organ is affected such as the gut.

The range of symptoms most commonly reported are:

· GUT: IBS symptoms or colic in babies, chronic mouth ulcers, nausea, reflux

· SKIN: Hives, rashes

· AIRWAYS: Sinus, congestion, nasal polyps

· NEUROLOGICAL: headaches, migraines, extreme fatigue, flu-like aches & pains (feel like being ‘hit by a bus’), in kids- anger and defiance, reduced concentration & silly behaviour


If you react within 30 minutes of eating a food, it is generally not a FODMAP reaction. This is because it takes at least 4 hours for food to travel through the gut and reach the large intestine where IBS symptoms are triggered.

An exception to this is when eating stimulates the gut to thrust a high FODMAP food (eaten within the last 24 hours but has not yet reached the large intestine) into the large intestine where IBS symptoms are triggered.

Alternatively, there could be an underlying food chemical intolerance or food allergy. Food chemical intolerance tends to be more of a build-up in the system effect but quick reactions can occur if a high enough dose is consumed or if the personal threshold is crossed. Allergy reactions tend to be very quick.


A low FODMAP diet can bring relief within the first couple of days or the first week, unless sneaky (hidden) FODMAPs are lurking! This is because FODMAPs only trigger reactions while they remain in the gut. Once they are pooped out then they can’t affect you, although it may take a few days to up to a week for your gut to feel normal again (recovery).

In contrast, food chemicals are absorbed into the body and take longer to be broken down and excreted via the kidneys. Three to four weeks is usually needed to exit the system so symptoms tend to last longer.

If the low FODMAP diet is not working well enough for you then food chemical intolerance may be worth exploring either separately or in combination with the low FODMAP diet. If you have non FODMAP food related symptoms such as a sore tongue, chronic mouth ulcers or rashes/itchy skin then food chemical sensitivities may be in play.

Troubleshoot with an experienced dietitian well versed in Food Intolerances and FODMAPs to explore the possibility of an undiagnosed food chemical intolerance.

Frances is an Accredited Practising Dietitian (APD) located in Melbourne, Australia. Frances' passion is helping people with symptoms of IBS pinpoint their food triggers using elimination diets, including the FODMAP and FAILSAFE elimination diets. If you're based in Melbourne and would like to see Frances to help you get to the bottom of your gut issues, click here to book an appointment.



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