Food Sensitivities: What They Are, When They Matter, and How to Heal: Focus on IBS, Migraines and Depression – Part 2

by , | August 8, 2022 | Articles, Gut Health, Nutrition

In our last article, we discussed the evidence that food sensitivities may play a role in some common, chronic conditions. Blood testing for immunoglobulin G (IgG) antibodies against everyday foods reveals significantly higher reactivity among people with symptoms as diverse as irritable bowel syndrome (IBS), migraine, and depression. But can this knowledge help us improve outcomes? Elimination diets based on IgG testing can be effective for all three of these conditions, holding promise for many more. We’ll unpack what the research says and discuss how to do it right, if it’s right for you.

Irritable Bowel Syndrome (IBS)

At least five clinical trials have tested IgG-based elimination diets in IBS and all have found improvements in symptoms and quality of life. Only one was a double-blind, randomized, controlled, clinical trial – the highest quality of scientific methodology when conducting research. 1 This team tested 150 IBS patients (all subtypes, meaning IBS with diarrhea, IBS with constipation and mixed IBS) and gave them either a personalized “true” elimination diet, excluding their high IgG foods, or a “sham” diet excluding the same number of non-reactive foods, for 12 weeks. IBS has a strong placebo effect, so 15% of people felt better on the sham diet, but among those fully adhering to a “true” elimination diet (no small feat!), 54% showed notable improvements on the IBS symptom severity score.

Two similar trials lacking placebo arms found 65% and 89% of participants experienced at least some improvements after 8 and 12 weeks of IgG-guided elimination diets, respectively. 2,3 As we discussed previously, not everyone with IBS has positive IgG levels, and those who didn’t were excluded from these studies. An integrative or functional medicine doctor or nutritionist can help you determine if an elimination diet might be right for you.

To reap lasting benefits from an elimination diet, it should be followed by a careful, professionally-monitored, and staged reintroduction phase. A strict elimination diet is not a long- term solution, even if it provides relief, as it can lead to nutrient deficiencies and complications. In the first trial, nearly everyone who improved felt worse when reintroducing eliminated foods freely. 1 But in another trial, participants introduced reactive foods one at a time after 3-4 weeks elimination and, if deemed to tolerate them by the clinician researchers, incorporated them in a 6-month rotation diet which encourages mixing up food choices to thwart reactivity. 4 Symptom improvements held, and repeat IgG testing showed a 30% reduction in food sensitivities. Participants also took a probiotic, which may play a role in regulating the immune system response and maintaining symptom improvements long term.

There are many popular diets for IBS, but when several go head to head in a clinical trial, the IgG-based elimination diet appears to be the most effective. In a study on 73 women with mixed IBS, an 8-week personalized elimination diet showed better symptom reduction than the low FODMAPs diet or standard gastroenterologist dietary advice. 5 The elimination diet also improved coexisting migraine and skin symptoms, which the other diets did not improve. In the clinical setting, it is observed that the Institute of Functional Medicine elimination diet, along with the appropriate protocol for supporting selective intestinal permeability, is an effective tool for patients suffering from skin symptoms such as eczema and acne, as well as autoimmune conditions. It is important to speak to your qualified healthcare provider about the most appropriate, science-backed diagnostic tools and treatment approaches before embarking on an elimination diet, supplemental support or food sensitivity testing.


If you’ve tried everything for your migraines, an IgG elimination diet might be worth exploring with a qualified health professional. Three clinical trials have explored the benefits. In one study of people with self-reported migraine-like headaches (without a physician diagnosis), a “true” personalized IgG-based elimination diet reduced headache days by 12% more than a “sham” elimination diet after 4 weeks (using the method described above), but had no benefit at the end of 12 weeks. 6 So, self-diagnosed migraines are unlikely to benefit. However another trial in physician-diagnosed migraine patients without aura found that a “true” elimination diet reduced the number of both headache days and migraine attacks by 30% across 6 weeks versus a “sham” diet, though there was no reduction in intensity and the benefits disappeared as soon as the diet stopped. 7

The benefits, however, are greatest in those with the greatest need. A third study selected 56 migraine patients specifically because they had failed numerous other treatments, and found 43 (77%) reported no migraines at all after 1-6 months on the personalized elimination diet. 8 It may not be the first-line, but an elimination diet can be a life-changer for those who need it. A doctor trained in functional or integrative medicine can help you determine if you should try an IgG- based elimination diet.

Migraine and IBS are common comorbidities, and the benefits of IgG testing and food elimination are even greater when the two present together. Two studies found significant improvements in both migraine and IBS symptom severity and frequency in 6 and 14-week elimination diets, with the benefits appearing to get better over time. 9,10 The categories of foods most reactive for migraineurs appear to vary geographically. In Turkey and South China, spices, nuts, seeds, grains, and seafood top the list, while meat, salads, mushrooms, and yeast are consistently the least reactive. 7,9,10 However, a cohort from Mexico reacted mostly to egg, dairy, yeast, wheat, tomato, pork, and beans. 8


Despite the striking evidence that depressed individuals have significant rates of food sensitivity, there have been no clinical trials for IgG-based elimination diets in major depressive disorder. A single case report of a 34-year-old female with MDD described her greatly improved mood on a generic elimination diet, which worsened whenever easing the restrictions and improved when recommitting. 11 Subsequent IgG testing confirmed dairy and gluten sensitivity, and avoiding these foods has allowed long term improvements. Personalization through testing can be powerful, but more studies are needed to better understand the impact of these interventions.

What Does This Mean for You?

In summary, testing for and eliminating IgG-reactive foods from your diet may be a valuable part of your healing journey. IBS, migraine, and depression have received the most recent research attention, but the benefits of testing and treating food sensitivities may extend beyond these three conditions. Not to all conditions, though. A well-designed trial published in the prestigious journal Lancet found that a radical elimination diet reduced behavior problems in a subset of children with ADHD, though reintroductions of both IgG-positive and negative foods consistently caused relapses. 12 Thus, an elimination diet was helpful in ADHD, but IgG testing was not. However, the study failed to consider a significant confounder: it is well-known that many children with ADHD benefit from consistency in daily routines. A radically-simplified diet may provide benefit in this case on a mental, not an immunological level.

In closing, it is important to make one thing clear: food sensitivities do not mean that everyday foods themselves are the problem. If your immune system is overreacting to the foods you eat, choosing different foods on an elimination diet can help to calm it down. But your immune system didn’t start overreacting in the first place because you ate the wrong foods – it reacts because it gets dysregulated. To address the root cause, we have to also assess and address the triggers of a dysregulated gut-associated immune system.

The science is still unfolding around how this dysregulation occurs and leads to food sensitivities, but there are important clues in the research. Toll-like receptors (TLRs) are some of the immune system’s sensors for danger signals, like pathogenic bacteria and viruses. IBS, migraine, and depression have all been associated with alterations in TLR signaling, 13–15 which could influence the inappropriate immune responses that cause food sensitivities. Increased intestinal permeability or “leaky gut” may play a role as well, by allowing intact food molecules and bacterial byproducts to come in contact with the immune system (and TLRs) behind the gut barrier. A systematic review of 27 studies in IBS found that especially diarrhea-predominant IBS is associated with leaky gut. 16 This correlates with the research we discussed in part 1 showing that food sensitivities are more prevalent in IBS-D than IBS-C or M. Recent research suggests that depression is associated with increased intestinal permeability, 17,18 and may correlate with its severity. 19 Many researchers have speculated a connection between leaky gut and migraine based on laboratory data, though clinical trials are lacking. 20

If you have been diagnosed with irritable bowel syndrome, migraines or depression, consider speaking to an integrative and/or functional medicine doctor about whether food sensitivity testing or an elimination diet is an appropriate next step in your care. It is important to be supervised by a qualified physician and nutritionist, to ensure that your diet is providing sufficient macro- and micronutrients, your intervention is the appropriate duration, and the elimination diet is followed by a methodological food reintroduction. A functional medicine doctor can further work to balance the microbiome with prebiotics and probiotics, support selective intestinal permeability with nutrients and herbs, and optimize digestive function while implementing an IgG-guided elimination diet can help retrain the gut’s immune system for the long term to keep us safe instead of causing harm.

Written by Jonah Udall; Select sections of article written by and article reviewed by Dr. Bojana Jankovic Weatherly. Jonah Udall is a nutritionist, herbalist, and functional medicine practitioner in-training, earning his Masters of Science in Human Nutrition and Functional Medicine at the University of Western States. Chronic health challenges taught him the importance of listening deeply, seeking the root causes of dysfunction, celebrating the individual, and finding collaborative paths to vibrant health with nature’s medicines. Jonah is also a professional musician and movement artist, director of New York City-based ECHOensemble, and a certified Deep Listening instructor.


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