Last month on the blog I shared Part 1 in this duo of posts that cover some basics about food allergies and food intolerance. Part 1 of the post looked at food allergies, with a spotlight on coeliac disease (which is an autoimmune condition). Part 2 focuses on food intolerance.
The term “food intolerance” is used in everyday speak to cover a very broad range of conditions. For the purposes of this article, let’s consider “food intolerance” to be any symptomatic adverse reaction to consuming a certain food or ingredient.
Unhelpfully – and confusingly – the signs/symptoms of food intolerance are pretty non-specific. Here is a list of some of commonly cited signs and symptoms courtesy of the Allergy UK website:
Aches and pains
Chronic fatigue syndrome
IBS (Irritable Bowel Syndrome)
A common example: Lactose intolerance
Lactose intolerance is actually a bit of a special food intolerance because it’s so well defined. Lactose intolerance occurs because some people are deficient in the enzyme lactase. Your pancreas produce a variety of digestive enzymes which get squirted into your digestive tract to help break down the particles of food you ingest. Lactase digests lactose, which is the primary sugar (yes, lactose is chemically a type of sugar) found in dairy. If you do not produce sufficient lactase, your body will struggle to digest lactose and you are likely to experience digestive discomfort including gas, bloating, stomach cramps, and diarrhea, which typically set in a few hours after you eat. You experience these symptoms because the undigested lactose sits in the small intestine instead of being digested and there it ferments, producing the gas and related digestive symptoms.
It is possible to run some tests to help confirm a true lactose intolerance; the most common test is a hydrogen breath test. You can read more about the relevant tests via this link.
This is NOT the same as an allergy to dairy. It also does NOT mean that you have to avoid absolutely all dairy products. People can experience intolerance in varying degrees (depending on whether they still produce small amounts of lactase). Some people may tolerate a small amount of lactose-containing food, or even a few small amounts spread throughout the day.
A controversial example: Gluten intolerance
Simply pop in a web search for “gluten intolerance” and you come up with a raft of articles each with a slightly different take and some that question whether an intolerance – outside of coeliac disease – exists at all. Non-Coeliac Gluten Sensitivity (NCGS) is frequently associated with symptoms including indigestion, bloating, gas and abdominal pain, which tend to occur a few hours after consuming a gluten-containing meal. Less often people also report “brain fog”, dizziness and/or lethargy, and sometimes even a rash or bumps on the skin. Diarrhea and/or constipation may also be reported as an ongoing issue.
Unlike lactose intolerance, NCGS does not have such a clear-cut cause. Layer that on top of the fact that it’s trendy to be “intolerant” these days and boom. Everyone has an opinion.
I think that the most correct perspective, based on what we know so far, is that some people do not tolerate gluten very well though they are not coeliac, but that the cause of perceived NCGS is not the same for each person – and in fact the culprit may not be, or just be, gluten. The perception of a sensitivity to gluten-containing foods may arise because of:
- Food based causes: (i) actual NCGS i.e. true sensitivity to gluten (not an autoimmune reaction as in coeliac disease, but nonetheless a symptomatic reaction to consuming gluten*) or (ii) a sensitivity to FODMAPs (fermentable oligosaccharides, dissaccharides, monosaccharides and polyols), certain chains of carbohydrates present in a variety of foods including many that also contain gluten. A sensitivity to FODMAPs is often mistaken for gluten intolerance (and is what was identified in many subjects in the press about a recent study which suggested NCGS may not exist).
- Body based causes: (i) Irritable Bowel Syndrome (an ongoing functional bowel condition associated with recurring periods of gastrointestinal distress, diarrhea/constipation etc. and which can be tied up with an intolerance of FODMAPs) or (ii) an otherwise temporarily irritated or inflamed gut lining due to things such as an infection, dysbiosis, trauma, stress or a different and undiagnosed food intolerance or allergy. The reason being that if the gut lining is damaged then maldigestion may result and make you feel like you’re responding poorly to gluten-containing food.
Intolerance NOT Allergy
A food intolerance is mediated by different pathways in the body compared to a true food allergy i.e. it is not a response by IgE immunoglobulins (refresh your knowledge using my previous post here). It is not associated with the usually rapid and potentially fatal (in the case of anaphylaxis) response of an allergy. This is not to say that a food intolerance won’t give you painful symptoms, but it’s different. Also, many cases of intolerance do not require total avoidance and individuals may be able to consume small amounts of the offending substance, whereas with an allergy it is essential that individuals strictly avoid the consumption of foods containing, or even prepared on the same equipment as, the substance.
This makes a difference to how you can choose and create meals for yourself at home and also has implications for when you’re eating out. It is helpful to be specific and let staff know what they need to do to accommodate your needs i.e. do they need to prepare your food separately or can the same utensils be used.
What can I do if I think I’m suffering from a food intolerance?
First of all, don’t just read this article. I am studying to become a nutritionist and I wanted to put some background information into a blog post for you, but if you are struggling with digestive discomfort take yourself to a professional and get personal advice. In the lead up to an appointment you may find it useful to keep a food diary for a few weeks so that you can discuss this with your practitioner and also give them an idea of what might be giving you grief.
For most food intolerance, there isn’t a specific, 100% diagnostic test. But…hold on…there appear to be a lot of intolerance tests available? Unfortunately, many of these are unsupported by credible scientific method, and research is ongoing in this field**. The “gold standard” of food intolerance diagnosis is often still an exclusion/re-introduction diet – but this doesn’t mean that you should put yourself on an extensive elimination plan on your own…
Take a sensible approach to food intolerance
- Keep a food diary;
- Seek professional advice if you experience gastrointestinal symptoms that bother you;
- Understand your limits if you have a food intolerance and become familiar with common ingredients and food labeling so you can pick things that are helpful for your digestion (again, seeking professional, personal advice may be helpful here so you understand what foods and food groups will sit well with you);
- Don’t just jump on a strict elimination diet bandwagon;
- If you are scared of eating certain foods, worried about whether you’re doing enough “clean eating”, or feel upset about the food that you eat in any way… also talk to someone. A food intolerance has nothing to do with being healthy (though if you have one and it’s managed well, then you might feel better!). But remember. You can cut out gluten and still eat a load of processed crap. You can eat milk and cheese and be fit as a fiddle and your gut can be happy.
This has been an enormous article and I really want to write more, in particular about FODMAPs as I know that many people experience difficulties with these (me included), but I will save it for another piece. I want to hear from you – do you have a food intolerance? Have you ever been professionally tested? How do you manage your intolerance?
*Note that NCGS is not associated with the same significant, harmful degree of destruction of the intestinal villi as occurs in coeliac disease (in coeliac disease, the body actually attacks itself and causes serious damage to the small intestine when gluten is consumed). NCGS may give you a painful or bloated tummy but in the vast majority of cases won’t eat away at the intestinal lining like coeliac disease. In short; if you are coeliac, eating gluten is really damaging; if you are NCGS, you might not suffer as badly if you nibble the bread basket pre-dinner, though you may feel unwell and there may be some gastrointestinal distress (it varies depending on the degree of sensitivity).
**For a sample article summarising and criticising some current food intolerance tests, see this article. I’m not coming down unfairly on the available tests by the way; I think that certain tests can be used to help guide intolerance management but I just want to make sure you’re aware of the fact that there’s bogus stuff out there and that you should be cautious and tests need to be interpreted carefully. Even natural medicine or integrative medicine practitioners who use some tests are aware of the limitations; for example see this discussion by Chris Kresser here.
Above Image Credit: foodiesfeed.com
Thank you for writing this! So informative and so important for people to understand the difference between allergies and intolerances since a lot of people think they are the same thing. I would love to see an article on FODMAPs, I was recently put on a low FODMAP diet for a few months by my doctor for my SIBO and actually noticed a worsening of my symptoms until I went back to including FODMAPs! Would love to hear your perspective on a low FODMAP diet/experience with reducing FODMAPs!
Hi Christina, thank you so much for this really thoughtful and considered comment, I’m so glad you liked the article 🙂 It’s funny you mentioned FODMAPs; that’s actually next on my list of articles in this subject area and I’ve already got a draft underway! Stay tuned! x