11 Warning Signs You Have A Sneaky Food Intolerance


[Last updated 25th October, 2018]

Do some foods just not sit right with you?

Have you noticed that it was not just a one-off, but rather part of a trend or pattern of symptoms?

Food intolerance (also known as food sensitivity) is much more common than you think. Up to 10% of people experience it to some degree, yet most don’t do anything about it.

Not to be confused with food allergy (which involves the immune system), a food intolerance reaction occurs when an individual’s threshold to certain food compounds or chemicals is exceeded. Symptoms can occur hours – even days – after eating the offending food.

Scroll through and see if you experience any of the following signs of food intolerance:

1. You’re rushing to the toilet numerous times per day

Rushing to the toilet often food intoleranceDo you ever consider not eating somewhere or attending an event where there may not be good bathrooms?

This is quite a common mindset of someone with a strong food intolerance, as the most direct and immediate symptom is digestive stress. This includes things like severe abdominal paingas, bloating, and diarrhea–  the hallmark of Irritable Bowel Syndrome (IBS).

The main cause of IBS is thought to be fermentable, poorly absorbed carbohydrates known as FODMAPs. The concept of FODMAPs was developed through research at Monash University, and they continue to be the leading authority on the topic.

The only scientifically-proven dietary treatment for IBS is called a Low FODMAP Diet, with a success rate of up to 76% (1).

2. You experience chronic muscle or joint pain that tends to be widespread

You experience chronic muscle or joint pain that tends to be widespreadDo you suffer from long-term muscle tenderness or joint pain that impacts your day-to-day activities?

Fibromyalgia is a newly-recognised medical condition that affects up to 6% of the population, especially middle-aged women. It is characterised by long-term and widespread pain that is not specific to one particular area (2).

Many fibromyalgia patients report that symtpoms are often triggered by foods they eat. In fact, one study found that almost 50% of those with fibromyalgia reported their symptoms worsened after eating certain foods (3).

Discovering your own food sensitivities, and then cutting down or abstaining completely from those trigger foods, may be the most important thing you can do to treat this condition.

3. Caffeine sends your system into overdrive

caffeine intoleranceIt’s no secret that caffeine is a stimulant.

That’s the major reason coffee is the most popular hot beverage in so many countries.

But some of us are caffeine intolerant (myself included). This is because how well your body metabolises caffeine is actually determined by your genes.  In fact, with the advances in genetic testing it is now possible to test if you are sensitive to caffeine or not.

For those considered “slow” metabolisers of caffeine, a strong coffee can lead to digestive stress, sweating, raised blood pressure, and potentially even an increased risk of heart disease with regular consumption (4).

4. You experience frequent headaches or migraines after certain meals

You experience frequent headaches or migraines after certain mealsThis is quite a common symptom of food intolerance, and largely avoidable when you know what the triggers are.

The most well-known food chemical trigger is Monosodium Glutamate (MSG).

Research shows that those with a sensitivity to dietary glutamate can experience headaches, muscle tightness, numbness/tingling, and weakness after ingesting large amounts (5). Symptoms can take several hours before they hit.

5. You constantly feel exhausted despite sleeping well

Excessive fatigue can be a symptom of food intoleranceDo you often feel exhausted? Not just physically, but mentally and emotionally as well?

Chronic fatigue syndrome is a disorder characterised by severe long-term fatigue that affects a person’s ability to carry out regular everyday activities. It’s estimated that between 1 to 4 million Americans have the condition, yet less than 20% have been diagnosed.

The cause is not well-understood, but food intolerance has long been suspected as a major trigger alongside genetics, inflammation, stress and more. Exploring the best form of treatment is an ongoing process, but diet is likely to play an influential role (6, 7).

6. You don’t tolerate wheat products despite testing negative for celiac disease

You don’t tolerate wheat products despite testing negative for celiac diseaseGluten is a protein found in wheat and other grains that is known to cause digestive stress in certain people.

Those with celiac disease have a physiological response to gluten intake, which can be tested for.

But it is thought between 0.5 to 13% of people who don’t have celiac disease still experience difficulties digesting gluten, a condition known as a Non-Celiac Gluten Sensitivity or Gluten Intolerance. While the mechanism is different to celiac disease, the symptoms are thought to be very similar (8).

Based on current evidence, those who do experience a bad reaction to gluten-containing foods (and don’t have celiac disease) should also consider FODMAPs as a trigger for symptoms (9).

7. You have an underactive thyroid (hypothyroidism)

What is an underactive thyroid (hypothyroidism)?An underactive thyroid (hypothyroidism in a medical context) refers to when the thyroid gland doesn’t produce enough thyroid hormones.

The strong majority of all hypothyroid cases are caused by an autoimmune disease known as Hashimoto’s. Preliminary studies suggest a strong link between Hashimoto’s and an intolerance to gluten (specifically celiac disease). In fact, around 16% of those with celiac disease have antibodies that attack the thyroid (10).

Several studies have also found that a gluten-free diet reduces the number of anti-thyroid antibodies, which is favourable for hypothyroid treatment and in preventing new issues (11, 12).

In other words those with an underactive thyroid may be more likely to have a food intolerance, namely gluten.

8. Milk and yoghurt upset your stomach

Milk and yoghurt upset your stomachLactose is the natural sugar found in milk. We require the enzyme Lactase to digest it properly.

But it is estimated that 65% of humans experience some difficulty in digesting lactose after infancy, with rates as high as 90% in those of East Asian decent. This is known as lactose intolerance and is one of the most widely-recognised food intolerances.

Reaction severity varies widely depending on the individual, but in most cases it can cause gastrointestinal symptoms similar to IBS.

9. Your rheumatoid arthritis continues to get worse

Rheumatoid arthritis and food intoleranceUnlike osteoarthritis, rheumatoid arthritis (RA) is not caused by standard wear-and-tear.

It’s almost always caused by a combination of genetics and environmental triggers, including diet. Much like with Hashimoto’s and celiac disease, it is thought that an autoimmune response to certain food compounds may trigger symptoms.

The theory is that certain food sensitivities may trigger an inflammatory immune response that prolongs or exacerbates the joint inflammation that causes the pain and swelling in RA patients (13). Note that this is only a theory and has not been proven or disproven .

Considering there is no known cure for RA, and the only dietary supplement that shows any (slim) promise is high-dose fish oil, eliminating the possibility of a food intolerance is a logical phase of treatment.

10. Certain foods give you rashes, eczema or other skin conditions

certain foods cause skin conditions like eczemaWe usually associate skin reactions with a food allergy because blood tests can supply a reasonable diagnosis for allergies.

But it is now well-understood that food intolerances can cause skin reactions too (such as eczema), albeit a much more delayed response than allergies.

Remember that with food intolerance most can tolerate a reasonable amount of the food compound, but if they eat too much (or too often) then symptoms begin to show.

A natural food chemical called Salicylate is one the biggest culprits when it comes to skin conditions, the other being Histamine. It has been proposed that roughly 2.5% of Europeans have a salicylate sensitivity (14).

While eliminating all salicylates is virtually impossible, limiting the amount consumed to within a tolerable threshold is most effective way to manage it. Tomatoes and peppers (also known as paprika or capsicum) are some stand-out sources of salicylates most commonly reported by patients.

11. You know that a meal rich in onions or garlic gives you gastro

Garlic can be a big triggerSome of the most common food triggers of digestive stress are onions and garlic.

This is because they are so commonly used to add flavour, yet are also extremely high in FODMAPs. More specifically, both contain fructans that are known triggers in those who are a bit sensitive.

While it’s best to cut them out of your diet during the elimination phase of a low FODMAP diet, there are a few workarounds for flavour, including using garlic-infused oils.

Do you experience any of these warning signs?

If you frequently experience one or more of these warning signs, you should consider trialling a Low FODMAP diet. I suggest you start with this 7-day diet plan.

Up to 10% of people experience food intolerance to some degree, yet most don’t realise or do anything about it. Here's 11 warning signs to look out for.

About Joe Leech, Dietitian (MSc Nutrition & Dietetics)

Joe Leech is a university-qualified dietitian from Australia.

He graduated with a Bachelor's degree in exercise science, followed by a Master's degree in Nutrition and Dietetics in 2011.

Learn more about him on the About page

21 responses to “11 Warning Signs You Have A Sneaky Food Intolerance”

  1. Great list! I know someone who could definitely use this article. She doesn’t want to believe she has a food intolerance, but all signs says she does. I’ll show this to her. Thank you so much!

  2. I have been trying to research this for a year now. Mayo clinic seems to have done research on Histamine Intolerance which seems to be somewhat linked to this. Is it the same thing or is this something different? Your article was amazing and easy to understand! Do you have an easy list of what to eat and not to eat? I have bought books on the Paleo diet. Is that a good diet to follow? I am a vegetarian, i know there are vegetarian choices also, correct? Thank you in advance for your help!

    • Hi Sue,
      Thanks for the kind words.
      Oh yes I’ve been meaning to do a write-up about histamine intolerance to clarify and make it simple to understand.
      So it is a different intolerance to FODMAPs. But taken from a 2007 study: The ingestion of histamine-rich food or of alcohol or drugs that release histamine or block DAO may provoke diarrhea, headache, rhinoconjunctival symptoms, asthma, hypotension, arrhythmia, urticaria, pruritus, flushing, and other conditions in patients with histamine intolerance.
      Do you mean a list for food intolerance, or just for healthy eating? What is the health aspect you are aiming to improve?
      You don’t need to worry about paleo, especially if you are vegetarian.

  3. I have lactose intolerance. I have to take Lactaid pills to consume dairy products at all, even cheese, which I love. Otherwise, I get bloated, I have gas, and 2 days later, I’ll have the diarrhea. In the meantime, my stomach will be cramping like no tomorrow.

  4. Hi my wife suffer from sibo is really hard for her to get herself to get to work because she constantly running to the bathroom. She is scare to eat anything because she has to go right after so if she is in the train or in the car she get very uncomfortable. This is the worst life someone could have. Please help

  5. I have active diverticulosis but recently have been experiencing symptoms of IBS. The diet plan for IBS is different from my normal eating habits, as I do not eat nuts, seeds or beef. What would I substitute for these items?

  6. Hello, I am suffering from chronic, episondic abdominal stomach spasms, gas, and bloating, accompanied by painful diarrhea. This has been going on for years, and I’m at my whit’s end.. After every single episode, I end up getting rashes all over my abdomen, back, spreading towards my arms and neck. These rashes last a few days, and then vanish, until the next attack . I had allergy blood tests, gallbladder; few small polyps, liver; small hemongioma and small cyst; follow up due in 6 months. Basically, I’m so far in the clear.
    So, what’s with the allergic reation????? Is it still food allergies, or food intolerance? I do have irritable bowel. As an asthmatic, my symptoms have been well under control over the past 40 years.

  7. Hi I have fibromyalgia and also a hyatusurnia. I suffer chronic pain and burning in my muscle fibres. I get a lot of tendonitis. I also think my lymph nodes do not work as they should. Do you think I would benefit from the FODMAP diet. Not sure I could do it on my own and I’m not sure if my doctors have a dietician with this knowledge. Your pages are very interesting and I have downloaded the info to take to my doctors .

  8. Hi .I had a flexible Sigmoidoscopy ,suspect diverticulosis, it was confirmed, some diverticula.
    Trying to find the foods that seem to upset me isn’t easy, so I was wondering if this would help me to find foods that upset my stomach.
    For sometime before the first episode of diverticulosis, I was aware of some foods that didn’t suited me.

  9. This list has this and that on it, but when I eat fruits I tremble and shake and need the bathroom and end up in great abdominal pain. Exhaustion, my cell count is low for both. but no one will listen that fodmap works but doesn’t work for me. I’m dying for something sweet but it gives me a bad reaction and that’s not helping the stress which isn’t helping the condition, I’ve heard. I get a lot of mucus dscharge vaginally when I eat sweet things and fruit, or some other food that bothers me like pork, onions, garlic, certain nuts, not even lactose free milk works for me because of the sugar in it or maybe it’s something else, I don’t know- which I’ve stopped eating- all the ‘tols bother me like crazy that even brushing my teeth with sensadyne screwed me up with rapid heart beat for hours. It ruined my sleep. Please, help me get my sweet back, however slight.

  10. this list definitly helped me out, I knew I was lactose. I also do have a question could oranges create some digestive problems as well ?

    • Oranges most definitly can cause stomach problems due to their high citric acid content. I had a friend who was extremely sensitive to oranges and would get severe cramps and explosive diarrhea from eating them. So YES, oranges can definitly cause digestive problems in those who are sensitive to them, as well as with regular people if they eat a lot of oranges (or drink a lot of orange juice). Also, orange juice is high on the FODMAP diet. Please talk to your doctor if you’re experiencing any stomach problems after eating certain foods. Your doctor can advise you much better than strangers on the internet can. Good luck!

    • Yes, exactly as Shaffer says, only its the SOLUBLE FIBRE that is the problem. Oats and oranges both cause me grief. And I’ve got IBS and do low fodmap, except for foods that hurt me.

  11. I have just about all these things on this list ….?
    Why does my heart feel like it beating out of my chest , I get very hot have to go the bathroom, after even just 2 glasses of wine… Hashimoto’s & pre diabetes( diet managed) I drink very little , I eat Paleo. I use what the diabetic dietitian told me to do an I apply it to Paleo! Taking Dairy & Gluten was key for me cleared up my acid reflux & elbow Eczema !! I have noticed that I have issues with Kumbatcha(sp) & vinegars sometimes but not the same extent, those are fermented. (feel like they are more histamine , an sometime wine does that too) have done the whole 3 months without any alcohol thing … I am not sure but I wonder its the sugar intolerance with that with wine .. I am drinking dry!

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