One of the most overwhelming aspects of daily life for patients with mast cell activation syndrome (MCAS) lies in dietary decisions, particularly when the gastrointestinal system is inflamed or dysfunctional.

Heidi Turner, MS, RDN is an Integrative Registered Dietitian and Nutritionist who works with patients with MCAS and other chronic conditions at her practice Food Logic in Seattle, Washington. She is passionate about increasing education and awareness for the mast cell activation syndrome patient population and is a wonderful resource with an abundance of clinical expertise in this area.

In a 2018 interview, Heidi shared some insight into nutritional strategies that may assist this patient population. Ultimately, the bottom line is that there’s no cookie-cutter approach to navigating the tricky world of diet with patients who have MCAS. It’s crucial that the approach is individualized and guided with the help of a licensed professional. However, she notes that the tendency is for patients to jump on the internet and start experimenting with things, an approach that can certainly lead to trouble.1

It’s quite difficult to give generalized dietary advice due to the spectrum of characteristics possible with patients who have MCAS. And by the time patients end up in Heidi’s office, they are typically extremely restricted in what they can do dietarily.1

As a general approach, Heidi tends to start by reviewing the basics: Has the patient already looked at the usual food suspects like gluten and dairy? Are they being exposed to processing, chemicals or pesticides in their diet?1

Once these areas are addressed and the obvious factors (like true allergies) are considered, Heidi tends to start thinking through the lens of histamine. She notes that while some patients do fine, for others, foods with high histamine content may be adding to the bucket. In these patients, it’s most likely that their DAO and HNMT (histamine breakdown) systems are overtaxed, so removing that constellation of foods can temporarily calm the system down.1

The next consideration is typically investigating whether the patient is being influenced by high FODMAP foods. Heidi notes that, particularly in patients who have small bacterial intestinal overgrowth (SIBO) or are in a dysbiotic state, fermentation can be adding to the overall histamine load.1 In 2017, researchers McIntosh and colleagues found that a 3-week low FODMAP diet reduced circulating histamine levels by 8-fold.2

If the above doesn’t work, Heidi may then resort to investigating other factors like salicylate, oxalate and sulfur intolerances with her patients who have MCAS. However, she notes that these areas tend to be the “bottom of the pyramid” in terms of priority, as they involve great difficulty to implement and are generally utilized for the more severe cases.1

For some patients, there’s no discernible pattern. Heidi notes that, in a subgroup of patients with MCAS, the issue is not necessarily a class or type of food, but that the digestive process is so taxed that anything entering it is reactive. She clarifies, “The digestive tract is a large immune system and sometimes becomes overly hypersensitive, leading to reactivity to the digestive process itself.”1

At the end of the day, Heidi’s approach tends to be more focused on the big picture in terms of helping calm down the system and get the gastrointestinal system moving optimally and with more options for increased “input” over time. She notes that you have to be careful, because if you take too much out, the body adapts. Heidi adds, “We’re dealing with a petulant child of an immune system that doesn’t want to be messed with.” Removal of non-trigger foods on the premise of their content of a particular substance can sometimes backfire and cause more sensitivities. This is one of the many reasons why it’s so important to work together with a professional throughout this process.1

Heidi Turner, MS, RDN practices at Food Logic in Seattle, Washington

Heidi explains that she doesn’t tend to see a lot of true allergies in patients with MCAS, but more often she notes reactivities. Reactivities to a food one day that was previously tolerated prior to that point is more of an indicator that the body’s pathways are struggling; the pathway is in disorder which can create a bigger build-up of histamine. A number of daily factors (like environment, stress, time of day) can influence chemical mediator levels and create day to day variations in the bucket spill-over effect. Heidi notes, “It’s not that the patient has allergies to these foods… it’s that the body does not want to digest them.”1

Aside from dietary modifications, Heidi also works with patients to optimize gastrointestinal bacterial balance, facilitate optimal levels of stomach acid and digestive enzymes, assist the body in removal of toxins with binders, and upregulate the parasympathetic nervous system (PNS). Just as there is no single approach to medications or dietary strategies, Heidi notes that probiotic supplementation advice is individualized. While many patients with MCAS don’t tolerate any probiotic very well, she recommends starting small and going with single strain options.1

Stomach acid is a common concern for patients who have MCAS. Heidi notes that hypochlorhydria (low stomach acid) seems more common in this patient population, particularly in patients with chronic constipation and delayed gastrointestinal transit issues. For these patients, she tends to see positive results with digestive bitters sprayed on the tongue before a meal. She recommends Better Bitters by Herb Pharm which may help stimulate the gut and the vagus nerve to let the body know that food is on the way. Many patients with MCAS may end up on a high protein diet following food eliminations and Heidi explains that the more we can help the body process proteins, the better, since high protein combined with low stomach acid may go hand in hand with a poorly functioning vagus nerve and gastroparesis. For patients who present on the diarrhea end of the spectrum, hyperchlorhydria (high stomach acid) may be a bigger reality and these patients may need to work more in the medication realm to get things calmed down.1

Heidi’s focus is less on adding specific foods to influence motility and more on calming everything down in order to open the door and get more food and nutrients options in. She finds that magnesium and vitamin C supplements may be tolerated by this population (though high dose vitamin C appears to exacerbate some patients, particularly those who have interstitial cystitis). Epsom salt baths are a great option for gaining magnesium and assisting the body’s detoxification systems. Going as organic as possible is also important, and she suggests that patients prioritize shopping organic for the Environmental Working Group’s dirty dozen at a minimum.1

Heidi also notes that she is seeing a positive trend for the use of toxin binders (such as activated charcoal, Great Plains liquid bentonite clay, and GI detox products) in patients with MCAS. Specifically, she is getting about 80% positive feedback in tolerance to once-daily binder use from patients who are severely compromised. Of course, caution and assistance are warranted with binders as they can also compromise nutrients and medication absorption when not used properly.1

Lastly, Heidi discusses the importance of addressing the parasympathetic nervous system which is often poorly functioning in patients with MCAS. She recommends utilizing exercises for the vagus nerve, exercises for breathing patterns, acupuncture (or acupressure if needles are not tolerated), visceral manipulation, and craniosacral therapies as useful adjuncts to nutritional approaches.1

At the end of the day, when it comes to nutrition considerations for the MCAS patient, the bottom line parallels other aspects of patient care: advice must be individualized and guided by a well-qualified professional. The importance of working with a nutrition expert who is familiar with MCAS, POTS, EDS and other comorbidities cannot be underestimated. Patience and discipline are essential aspects of the gut healing process, but the rewards can be plentiful when the patient has a comprehensive and holistic medical team in place to help them navigate the proper path.

You can learn more about Heidi’s clinical practice here:



  1. Turner H. Phone interview on July 13, 2018.
  2. McIntosh K, Reed DE, Schneider T, et al. FODMAPs alter symptoms and the metabolome of patients with IBS: a randomised controlled trial. Gut. 2017;66(7):1241-1251. doi:10.1136/gutjnl-2015-311339


This content is Copyright © Mast Cells United and is not intended to diagnose or treat anyone. Always consult your medical professional for any health guidance or advice.

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