Dr. Michael Ruscio, DC is a clinician, Naturopathic Practitioner, clinical researcher, author, and adjunct professor at the University of Bridgeport. His work has been published in peer-reviewed medical journals and he speaks at conferences around the globe.
Understanding How Diet May Improve Mast Cell Activation Syndrome
The best mast cell activation syndrome diet is the simplest, least-restrictive option that effectively treats your symptoms.
MCAS is an overactivation of the immune system, and since the majority of your immune cells are in your gut, digestive health is essential to immune health.
A great way to start improving MCAS is with a good elimination diet (like Paleo), and only moving on to a more restrictive diet if symptoms persist.
Regardless of which MCAS diet you’re on, it can be modified to contain a low histamine component to address any stubborn MCAS symptoms.
A low FODMAP diet is a good option for those with MCAS who also have significant gut symptoms that don’t respond to a simpler elimination diet.
High FODMAP foods such as onions, fermented foods, and broccoli have been shown to increase mast cell activation and cause histamine release.
Whichever diet you choose, you will want to add fiber at a level that works for you as it can be helpful in MCAS. But too much fiber may increase symptoms in some people, so take it slow.
If you feel like you are sensitive to everything — food, fragrances, heat, and, well, things you may not even know about yet — then you may be dealing with mast cell activation syndrome (MCAS). The hallmark of MCAS is an immune system that’s in overdrive, where anything and everything that you encounter can cause an immune reaction.
While research is lacking on mast cell activation syndrome diets, we see in the clinic that patients with MCAS benefit greatly by focusing on repairing gut health. Though the exact relationship between mast cells and the gut is unclear, we know that the gut microbiome affects the release of histamine. Some evidence even suggests that hyperactive mast cells may lead to serious gut disorders, like inflammatory bowel disease.
Everyone who has MCAS has different symptoms, severity, and triggers (like fiber or leftovers), so it is important to find a mast cell activation syndrome diet that works for you. We find that many people do not need a highly-restrictive diet to get relief, instead starting with an elimination diet (such as a Paleo diet) and probiotics. Alternatively, we may move on to more specific diets, such as a low FODMAP diet and/or a low histamine diet in those with persistent symptoms.
Dealing with mast cell activation syndrome is stressful enough, so you want to find a diet that helps your symptoms, but that is not adding overwhelm and stress. In this article, we will take a look at what mast cell activation is, how it is different from histamine intolerance, and what dietary interventions may help improve symptoms.
Quick Guide to Mast Cell Activation Syndrome (MCAS)
What are mast cells, and why might they be causing so many issues?
Mast cells are a normal part of our immune system. They are specific kinds of white blood cells that release inflammatory molecules, such as histamine, in response to various triggers, including environmental exposures, stress, and/or from certain foods.
Sometimes though, mast cells are triggered too often or when we do not really need them, and this can lead to too much inflammation and histamine in the body. This is why it seems like you are sensitive to almost everything — your immune system is on high alert and is sending histamine to try and help. This leads to the telltale MCAS symptoms of flushing, hives, rashes, headaches, and stomach pain.
While mast cells originate in the bone marrow, mature mast cells are most often found in the skin, gastrointestinal tract, and respiratory system — this is why you get such a wide range of symptoms, from rashes to diarrhea to runny nose .
I’ve compiled the most common symptoms into the following chart to make it easy to navigate. The chart is organized by organ system because one of the diagnostic criteria for MCAS is that the patient has intermittent and recurrent symptoms that affect at least two organ systems .
Diet is one of the main interventions used to help people with MCAS get symptom relief and start healing. Let’s break down why we want to look at diet and the relationship between MCAS and gut health.
Gut Health and MCAS
We are finding more and more of a link between the gut microbiome and MCAS, although more clinical research is needed to really understand what exactly is going on. Here is what we know so far, though:
There is some evidence that hyperactive mast cells may lead to IBD (inflammatory bowel disease) by causing an imbalance in the intestinal bacteria .
The microbiota in the gut can also influence mast cell activation .
Essentially, we know that the gut microbiota influences mast cells, and improving gut health can help decrease the overactivity of mast cells, and improve symptoms. The best way to improve gut health is through the right low-inflammatory diet for you (and we will talk about those options in a minute) and probiotics.
While we still do not know exactly how MCAS and gut health are linked, in the clinic, we often see that healing the gut is an effective, long-term way to reduce MCAS symptoms and improve any additional conditions such as IBS, IBD, and SIBO.
Now let’s take a closer look at the dietary options for MCAS.
The Best Mast Cell Activation Syndrome Diet
The best mast cell activation syndrome diet is the one that helps relieve your symptoms. This could be anything from a more general elimination Paleo diet, to a low FODMAP diet or even a combination of a low FODMAP/low histamine diet. How do you know which one is right for you? We will walk you through choosing the right mast cell activation syndrome diet for you and how the important role gut health plays in improving MCAS.
Though we currently do not have evidence-based diets for treating MCAS, a great comprehensive literature review on MCAS notes that a good starting point is to eat a whole foods diet that removes processed and high-preservative foods, additives, and alcohol (literature review). Favor gluten-free whole grains and fresh meat and produce and consider increasing your fiber intake.
Let’s take a closer look at the diets that are the best bet for MCAS relief. We’re going to start with the least restrictive option and then work our way up for those who have persistent symptoms. Then we’ll cover other steps you can take if you continue to struggle with symptoms after putting these diets to the test.
Option 1) General Elimination Diet
In the clinic, I take a stepped approach to improving MCAS symptoms. This helps people get the most relief with the least amount of overwhelm. Most often, we start with an initial elimination diet, such as the Paleo diet, with probiotics, and go from there.
Preliminary research suggests that a nutrient-dense diet with plenty of fiber may help calm mast cells [5, 7]. A Paleo diet removes many of the most common inflammatory foods to the gut, such as grains, legumes, and dairy, and can really help heal the gut lining and calm down any inflammatory response. It is full of nutrient-dense vegetables and meat and is fiber-rich, which has been shown to be helpful for MCAS.
A quick note on fiber: increase fiber slowly, as people with gastrointestinal symptoms often struggle with digesting large amounts of fiber and get abdominal pain, especially if they did not eat that much before. As your gut heals, digestion will improve and you will be able to eat a higher fiber content diet.
Dietary changes take a few weeks to help heal the gut and immune system, so stick with your chosen diet change for a month before you make more significant changes. As you are testing out your dietary changes, track your symptoms and note your improvement. Note if you see a decrease in flares and/or if some of your recurring symptoms get better. Keep up with the diet until you are better, or if your improvement plateaus.
If you’re still struggling with symptoms after using this starter elimination diet, I often recommend moving on to a low-FODMAP diet, which can be combined with a low-histamine diet if you are eating high-histamine foods and have stubborn MCAS symptoms.
Option 2) Low FODMAP Diet
If you are really struggling with persistent MCAS and/or digestive symptoms, then you may want to make some additional dietary changes that have been found to be helpful. In particular, making changes that help support your gut health and stabilize mast cells with a low FODMAP diet. For people with MCAS, high FODMAP foods may be part of what is causing mast cell activation and gut dysbiosis (as seen in rodent studies) .
FODMAPs (fermentable oligosaccharides, disaccharides, monosaccharides, and polyols) are fermentable carbohydrates. Many people eat these carbohydrates without issue, but some are unable to break them down, and/or the carbohydrates ferment too much (often because of gut bacteria dysbiosis.) This may cause symptoms of stomach pain, bloating, and diarrhea.
High FODMAP diets can increase urinary histamine, whereas a low FODMAP diet reduces it. This, along with animal research, suggests that high FODMAP foods could produce histamine that activates mast cells .
One study in mice found that a high FODMAP diet raised lipopolysaccharide (LPS) levels in mice, increasing mast cell activation and gut wall permeability aka leaky gut. In contrast, a low FODMAP diet calmed their mast cells, reduced LPS, and stopped leaky gut, improving their gut health .
Preliminary evidence suggests that a low histamine diet or a low FODMAP diet may help some MCAS patients (literature review), [8, 9]. While many patients find benefit with one diet, some may require a combination for the most relief.
Option 3) Low Histamine Diet
If you have looked into histamine intolerance, you will see that a low histamine diet is often recommended for people who have histamine intolerance, but does it work for MCAS?
Though there’s not enough research to definitely show that it does, I’ve seen it work for many at the clinic. While MCAS comes with high histamine levels, it is a complicated syndrome that we don’t fully understand. However, many with MCAS have found relief on a low histamine diet, making it a valuable option that can be combined with other diets, like Paleo or low FODMAP.
One literature review looked at using a low histamine diet to treat MCAS. It noted that dietary histamine is clearly correlated with histamine intolerance, but more research is needed to understand how and if dietary histamine affects MCAS.
While the link between high-histamine foods and MCAS is unclear at this time, a low-histamine diet can be effective for treating digestive issues, which often accompany MCAS. One study in the review found that 58% of IBS patients perceived worsening symptoms after eating histamine-releasing foods.
A low histamine diet removes foods that have high histamine content. These foods are typically anything that has been fermented, cooked for long periods of time (slow cooking), or leftover foods. Histamine builds up in these foods as they cook, sit in the fridge, or ferment. Typically people remove fermented foods, stop using slow cooking methods, and immediately freeze leftovers rather than leaving them in a refrigerator to avoid extra histamine.
Some common high histamine foods that you would want to avoid are :
Foods to Avoid
Naturally High in Histamine
Slow Cooked Foods
Crock pot cooked foods
Pressure cooked foods
Any food that is left out at parties or events
Leftovers kept in the refrigerator (freeze leftovers immediately after cooking)
Because MCAS and histamine intolerance have so much overlap, there is a lot of confusing information out there promoting a low histamine diet as a proven treatment for MCAS. While a low histamine diet often does help people with MCAS, it is important to note that they are not the same syndrome. Unlike MCAS, symptoms of histamine intolerance occur only when eating, and not all MCAS patients find relief from a low histamine diet (literature review.)
However because the immune system of people with MCAS is so overactive, removing high histamine foods can be very helpful for people with MCAS, to help improve symptoms. As a caveat, many of the above foods, like bone broth and sauerkraut, have many health benefits. If removing these foods doesn’t help reduce your symptoms, then keeping them out may be more of a detriment than it is beneficial.
Option 4) A Low Histamine, Low FODMAP Combination
Some people may benefit from a combination of a low FODMAP with a low histamine diet. I generally reserve this for people who, after using an elimination diet alone, still seem to be reacting to everything. If a low FODMAP diet improved many of your symptoms like pain, bloating, and diarrhea, but you still aren’t where you’d like to be, this can be a good option for you.
We also remove high histamine foods because: 1) some high histamine foods, like sauerkraut, are also high FODMAP foods; and 2) if high FODMAP foods activate your mast cells, they may be primed to react to high histamine foods. This can create a vicious cycle that a low FODMAP/ low histamine diet can help tackle.
This diet combination has been successful with people with more severe symptoms. The goal is that over time, as your gut heals and mast cell activation decreases, you can expand your diet a bit more. Often, you can add higher FODMAP and higher histamine foods back into your diet.
Another Gut Fix: Probiotics for MCAS
Along with diet, I often recommend adding in a good probiotic supplement to help improve gut health which, in turn, may decrease MCAS symptoms.
Probiotics can help improve the balance of your gut bacteria [11, 12], which is important for your immune system. And remember, mast cell activation syndrome is an overactivation of your immune system.
Your gut contains the largest concentration of immune cells in your body. Probiotics create a healthy immune response in your gut . Because probiotics are so beneficial to your health, they should be included in a daily health plan if you are dealing with chronic health symptoms. Fortunately, adding in probiotics does not need to be complicated, and you can find the best way to incorporate probiotics into your health with our Probiotics Starter Guide.
Sometimes further help may be needed, such as other interventions like quercetin. In those cases, it is best to work with an MCAS specialist, who may also recommend temporary antihistamines.
Common Symptoms and Diagnosis
Diagnosing MCAS is difficult because there are so many symptoms, they often come and go and are not consistent, and it is hard to pinpoint symptom triggers. There are a few lab tests that may be used, but, it can be hard to time a blood draw for when you’re experiencing a flare.
Additionally, MCAS is not yet widely known among doctors. While conventional doctors may not think to check for MCAS, some estimate that it might affect up to 17% of the population .
To learn more about MCAS, check out my interviews with Dr. Lawrence Afrin on the podcast (Part 1 and Part 2), as they can really help give you hope and understanding of this syndrome that might be causing your issues.
There are three criteria that can be looked at in diagnosing MCAS. A doctor may look at one or all of these criteria.
Patient has intermittent and recurrent symptoms of mast cell mediator release (symptoms in the above chart) that affect at least two organ systems .
Symptoms resolve completely or become less frequent or severe after taking antihistamines, leukotriene blockers, and/or mast cell stabilizers .
Blood or urine tests show a validated serum marker of MCAS, such as tryptase , or elevated metabolites of mast cell mediators during a flare (literature review) (I do want to note here that lab test timing is very difficult since it needs to be done during a flare.)
You will want to work with a doctor well-versed in MCAS to get a proper diagnosis by using the criteria above, and ruling out other things that look very similar such as systemic mastocytosis, histamine intolerance, and other inflammatory conditions. Also, there are a few diagnostic options that we often see suggested on the internet that’s not been found to be reliable.
Intestinal or other biopsy tests looking for mast cells have not been shown to be useful in diagnosing MCAS (literature review.) Additionally, some have claimed that dermatographia (skin writing) can be used as a diagnostic tool. You’ll often be prompted to take your fingernail and lightly scratch or write, on your skin and see if a raised red line appears and resolves within 30 minutes . This is not a way to diagnose MCAS. It is only a way to diagnose the symptom of dermatographia.
Is it MCAS or Histamine Intolerance?
You may hear MCAS also called “histamine intolerance,” but they are not the same thing, although they have overlapping symptoms and both involve high levels of histamine.
In histamine intolerance, too much histamine has built up in your body because: 1) you lack diamine oxidase (DAO), an enzyme that breaks down histamine, 2) certain gut microbes are making too much histamine, or 3) you eat a lot of high histamine foods (literature review.)
Whereas in MCAS, there are three subtypes, each with a different cause :
Primary MCAS is caused by an identifiable KIT gene mutation.
Secondary MCAS is caused by underlying IgE-dependent (immunoglobin E) allergy or another identifiable IgE-dependent trigger.
Idiopathic MCAS has no clear cause.
As you can see, there is a lot of confusion about MCAS vs. histamine intolerance, and even how MCAS is diagnosed. I hope this summary helps give you the resources you need to start your healing journey.
A Mast Cell Activation Syndrome Diet Can Put a Stop to Your Symptoms
Treating MCAS can be complicated because of its wide variety of symptoms and how difficult it is to find a specialist who really knows how to diagnose and treat MCAS. If you have tried diet after diet, and maybe even had test after test from multiple doctors, and you still have not found relief from symptoms, a good starting place is to improve your gut health.
Start with a month of a simple nutrient-dense and fiber-rich elimination diet along with a probiotic, and see how you progress — a Paleo diet is a great place to start.
If you still have symptoms after a month, you can consider removing high-histamine foods. If you are someone that has pretty severe general MCAS symptoms along with significant gastrointestinal issues, combining a low histamine diet with a low FODMAP Paleo diet may be a good choice for you.
If you are not seeing enough results or you hit a plateau, and you want to work with a clinician that has experience in MCAS, we are always happy to help at the Ruscio Institute for Functional Medicine.
I hope that this article has given you a better understanding of how to eat for mast cell activation syndrome, and has given you a clear path forward to feeling better.
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