The Definitive Guide to the Mast Cell Activation Syndrome Diet

Mast cell activation syndrome (MCAS) is a condition in which immune cells called mast cells are excessively active, releasing large amounts of chemicals like histamine. The release of these chemicals can trigger a vast array of symptoms in diverse parts of the body.

People with MCAS often find that certain foods trigger their symptoms; this can make eating challenging, to say the least! I’ve been there, dealing with MCAS related to Lyme disease and toxic mold illness. Throughout my healing journey and professional experience working with clients, I’ve curated a nutritional approach for MCAS that can reduce symptoms and address several of the fundamental underlying causes of MCAS, including leaky gut and dysbiosis. Are you dealing with MCAS and reacting to many foods? Read on to learn about the mast cell activation syndrome diet and how it may aid your MCAS recovery.

low-histamine vegetables that you can eat on the mast cell activation syndrome diet, including carrots, radishes, and bok choy

What is Mast Cell Activation Syndrome?

Mast cells are immune cells that release pro-inflammatory mediators, including histamine, in response to allergens and other threats to cellular health, such as bacterial and fungal microorganisms. (1, 2) They are a crucial component of our bodies’ frontline immune system defenses. However, we can run into problems when mast cells become too active. Too much mast cell activity results in high levels of inflammatory mediators in the body, which can, in turn, trigger a vast array of symptoms. (3) Mast cell activation syndrome (MCAS) occurs when the body’s mast cells become overly active, secreting excessive amounts of inflammatory mediators like histamine. Mast cell activation syndrome symptoms can include:

  • Anaphylaxis (in response to foods)
  • Low blood pressure (hypotension)
  • Rapid heart rate (tachycardia)
  • Flushing
  • Swelling of the face or lips
  • Abdominal pain and/or cramping
  • Diarrhea
  • Bloating
  • Nausea
  • Vomiting
  • Headaches
  • Shortness of breath

According to MCAS experts Dr. Lawrence B. Afrin, Dr. Mary Ackerley, Dr. Joseph H. Brewer, and their colleagues in a recent paper on MCAS, up to 17% of the general population may have MCAS. (4) Notably, MCAS differs from Mastocytosis, a condition characterized by excess mast cells in the body’s tissues.

What are the Causes of and Treatments for Mast Cell Activation Syndrome?

This article is not a definitive guide to mast cell activation treatment but a guide to the best MCAS diet. However, I’d like to provide a brief overview of mast cell activation treatments since it will enhance your understanding of the “why” behind the nutrition principles outlined in the mast cell activation syndrome diet.

The key to MCAS treatment is identifying the underlying causes driving hyperactive mast cells. Chronic infections, such as Lyme disease, and toxic mold exposure, may cause MCAS by stimulating mast cells. (5, 6) Imbalances in the gut microbiome and exposure to other types of toxins, such as heavy metals, may also contribute. (7, 8)

Many measures can be taken to address these underlying causes, including antibiotics and herbal antimicrobials for Lyme disease and co-infections, mold avoidance and detoxification for toxic mold illness, and gut healing strategies. While the root causes of MCAS are being addressed, many practitioners employ pharmaceutical mast cell stabilizers, such as Cromolyn sodium (Gastrocrom) and Ketotifen. Low-dose naltrexone (LDN) may also have some gentle mast cell stabilizing properties. Natural mast cell stabilizers may also be employed, such as quercetin. (9, 10) The mast cell activation syndrome diet can be used with these strategies to support the healing process.

Ideally, you should partner with a functional health provider to identify and address the root causes of your MCAS; doing this, in combination with the mast cell activation syndrome diet, will usually yield the best results.

The Mast Cell Activation Syndrome Diet

Food provides information to our bodies. We encourage healing when we choose the right foods for our unique health situation. However, when we choose foods that are not a good fit for our bodies’ needs, we can hinder healing. You have the power to help your body heal from MCAS by making intelligent decisions about your food!

The goals of the mast cell activation syndrome diet are to reduce the consumption of inflammatory foods, reduce the intake of high-histamine foods (if you are sensitive to dietary histamine), and incorporate anti-inflammatory and gut-healing foods that will calm down mast cells and support healing.

Foods to Avoid on the Mast Cell Activation Syndrome Diet

We must avoid foods with a high inflammatory potential to quiet down our mast cells. Here are some of the top dietary inflammatory triggers that can exacerbate MCAS symptoms:

Gluten

Almost without exception, I recommend that people with MCAS avoid gluten. Even if you don’t have celiac disease, gluten consumption can trigger mast cell activity in people with non-celiac gluten sensitivity (NCGS). In fact, mast cell activation may be one of the primary mechanisms driving symptoms, such as abdominal pain, in people with NCGS. (11)

Furthermore, most of the gluten-containing foods that people eat (bread, pasta, cereal) are also processed carbohydrates, which can disrupt the healthy balance of bacteria in the gut and promote gut dysbiosis. (12) Gut dysbiosis, in turn, is linked to mast cell issues. Not everyone with MCAS is sensitive to gluten, but, in my experience, enough people are that I think it makes sense to put this food on the “avoid” list.

Conventional Dairy Products

Conventional dairy products from factory-farmed, grain-fed animals frequently contain contaminants, including synthetic hormones (such as rBGH and synthetic glucocorticoids) and antibiotic residues (13, 14), that may trigger inflammation in individuals with MCAS. In addition, people who are sensitive to casein and whey, the two main proteins in dairy, may experience an inflammatory response to these proteins. If you are not sensitive to dairy products and want to include some dairy in your diet (it is a nutrient-dense food, if you tolerate it!), I recommend sticking with grass-fed and organic dairy products. Also, be careful with fermented dairy if you are histamine-sensitive since the fermentation process produces histamine.

Industrial Seed Oils

Industrial seed oils, including canola, corn, cottonseed, grape seed, safflower, soybean, and sunflower oils, are rich in omega-6 fatty acids. In preclinical research, a high intake of soybean oil is associated with an enhanced mast cell response. (15) The oxidized lipids found in vegetable oils trigger a chain reaction of oxidative stress in the body (16); oxidative stress can, in turn, activate mast cells. (17) To calm hyperactive mast cells, remove unhealthy vegetable oils from your diet and instead focus on eating anti-inflammatory fats, such as extra virgin olive oil and coconut oil.

Pesticide and Herbicide-Contaminated Foods

Try your best to purchase organic produce at the grocery store or from a local farm that may not necessarily be certified organic but hasn’t had chemicals applied to it during the growing process. This is crucial because pesticides and herbicides may disrupt our gut health and make our mast cells more sensitive.

For example, glyphosate, an herbicide that widely contaminates our food supply, induces the expression of an IL-33, an immune signaling molecule involved in Th2 allergy-oriented immune responses. IL-33 enhances the release of histamine from mast cells. (18) In other words, glyphosate exposure could be a triggering factor for mast cells.

I recognize that eating 100% organic isn’t doable for most people, which is ok! You can prioritize which types of vegetables and fruits to purchase organic and which ones you can buy conventional (and thereby save some money!). Choose organic foods as often as your budget allows, or refer to the Environmental Working Group’s Dirty Dozen list to prioritize which foods to purchase organic.

The Low-Histamine Diet and MCAS

In my nutrition practice, I’ve found that about half of my clients diagnosed with MCAS respond well to a low-histamine diet. In contrast, the other half doesn’t seem to notice a significant difference in their symptoms when they consume high-histamine foods, like sauerkraut, spinach, and strawberries. This may be because histamine is just one mediator released by mast cells, so people with MCAS who don’t react to high-histamine foods may have mast cells that predominantly release other inflammatory substances. Some people with MCAS may also have an enhanced ability to clear histamine from their bodies, making them less sensitive to dietary sources of histamine. These are just two of my theories!

If you have MCAS and have never tried a low-histamine diet, I recommend trying it for at least four weeks, as it may help alleviate your MCAS symptoms. Please note that the low-histamine MCAS diet isn’t meant to be followed forever. It should be used as a temporary therapeutic diet until your MCAS and histamine levels are better controlled.

Here are the guidelines for the low-histamine version of the MCAS diet.

High-Histamine Foods to Avoid:

  • Fermented foods, including fermented veggies like sauerkraut and kimchi, fermented dairy products like yogurt, kefir, and cheese, and kombucha
  • Alcoholic beverages
  • Vinegar
  • Chocolate and cacao (carob is a great low-histamine alternative to chocolate)
  • Cured meats
  • Smoked salmon and canned seafood
  • Slow-cooked bone broth. Pressure-cooked bone broth may be fine.
  • Spinach
  • Tomato, eggplant, and peppers
  • Avocado
  • Bananas (I find that plantains are fine for many histamine-sensitive people, even though they are in the same fruit family as bananas)
  • Strawberries
  • Citrus fruits
  • Soured foods, such as sourdough bread and buttermilk
  • Dried fruits, like dried apricots and figs

For some people, walnuts, cashews, peanuts, and pineapple also trigger histamine release.

If you don’t need a strict low-histamine version of the MCAS diet, then you can follow the overarching dietary principles outlined in this article while allowing yourself to have some histamine-containing foods, like spinach, avocado, strawberries, and modest amounts of fermented foods.

Leftovers also accumulate histamine. Tolerance for leftovers varies among people with MCAS and histamine sensitivity. Some can only tolerate leftover vegetables and not leftover proteins. In contrast, others can eat any type of leftover as long as it is consumed within 1-2 days of preparing it.

If you are very sensitive to leftovers and exhausted about preparing food from scratch every day, I recommend you try freezing leftovers and thawing them right before eating. Freezing can inhibit histamine accumulation in food better than simply refrigerating food.

fermented vegetables to avoid on the low-histamine diet for mast cell activation syndrome
Fermented vegetables, such as sauerkraut, pickles, and kimchi, are high in histamine and can worsen mast cell activation syndrome symptoms for some people with MCAS.

Foods to Eat on the Mast Cell Activation Syndrome Diet

One of the overarching goals of the MCAS diet is to eat an abundance of anti-inflammatory foods that will help quiet down mast cells and support gut health since the gut is a significant reservoir for mast cells.

Here are the foods to focus on:

Choose high-quality proteins

Fresh grass-fed beef and bison, organic and pastured poultry, organic or pastured eggs (as long as you’re not sensitive to eggs), and wild-caught seafood are excellent proteins to include on your mast cell activation syndrome diet. If you are histamine-sensitive, avoid cured meats like jerky, salami, and prosciutto.

Eat a wide variety of fresh organic vegetables and fruits.

Fresh produce will provide you with fiber that your gut bacteria can use to make butyrate, a crucial mast cell-stabilizing compound. (19) Many fruits and vegetables contain antihistamine and mast cell-stabilizing phytonutrients like quercetin and sulforaphane. (20) I recommend trying to eat at least 30 grams of fiber a day.

If you are histamine-sensitive, there are many low-histamine vegetables you can choose from, including kale, broccoli, cauliflower, zucchini, radishes, collard greens, watercress, and cabbage.

Choose cellular carbohydrates

Another name for processed, refined carbohydrates is “acellular carbs.” Acellular carbs are foods that contain carbohydrates that have been released from plant cell walls, creating a food with a high carbohydrate density. Think of bread, pasta, cereal, etc. where the carbohydrate has been broken down to make a flour-based food.

Acellular carbs will go through bacterial breakdown in the gastrointestinal tract much sooner than is appropriate for humans, fermenting in the small intestine rather than the large intestine, therefore raising the risk for gut dysbiosis (including possible small intestinal bacterial overgrowth, or SIBO).

A common misconception is that whole grains (oats, rice, etc.) are cellular, but they aren’t. At the time of the harvest whole grains have some fragments of cell wall in there indicating there were cells there once, but in reality, some of the cell wall has been broken down already, creating an acellular carb.

For people with MCAS, I recommend choosing “cellular carbs” instead to better support the gut microbiome and inflammation regulation. Cellular carbs are digested more slowly, producing a lower and slower rise in blood sugar and a healthier gut microbiota. Examples of cellular carbs include:

  • Whole fruits, like berries and apples
  • Starchy tubers, such as sweet potato, cassava, and taro
  • Root vegetables, such as parsnips, rutabaga, celery root, carrots, and beets
  • Winter squash, such as acorn, butternut, delicata, and kabocha squash
  • Plantains

Small amounts of grains and legumes may be fine on the mast cell activation syndrome diet, but I advise against making them your primary source of dietary carbohydrates.

Consume anti-inflammatory fats

Aim to eat various anti-inflammatory fats, including extra virgin olive oil, avocado oil (if you’re not histamine-sensitive), coconut oil, and ghee. The omega-3 fatty acids EPA and DHA are essential for regulating immune function, so try to eat several servings of fresh fatty cold-water fish a week, like salmon and halibut. (21)

Fresh nuts and seeds can also constitute a source of healthy fats in your MCAS diet. See the “FAQs for the Mast Cell Activation Syndrome Diet” section below for more information on nuts that may be more optimal for those with MCAS.

Focus on eating nutrient-dense foods

To recover from MCAS, you must meet your body’s needs for immune system-regulating micronutrients, such as vitamins C, A, D, and E. By regulating the immune system, these nutrients may reduce mast cell hyperexcitability and offer antihistamine effects. (22, 23, 24) A diet for MCAS recovery shouldn’t be focused just on the foods to avoid; we also need to prioritize nutrient density because if we’re not getting all of the nutrients that our immune system and gut need to repair, then our recovery from MCAS may be hindered.

If you’ve been on a limited diet for more than a few months at a time, you may be deficient in specific anti-inflammatory, immune system-regulating nutrients. If this sounds like you, you may want to pursue micronutrient testing with the help of a functional healthcare provider to determine your unique nutritional needs.

Watch Out for Food Additives!

Watch out for the following food additives, which may trigger mast cell activity and the release of inflammatory mediators like histamine:

  • Carrageenan: This is a derivative of seaweed commonly found in deli meats, dairy alternatives, and other processed foods.
  • Sodium Benzoate: Sodium benzoate is added to foods to prevent spoilage from bacteria and mold. It may trigger mast cell activation. (25)
  • Monosodium glutamate (MSG): This synthetic additive is used to impart an “umami” flavor to food. It is implicated in headaches and nausea. (26)
  • Citric Acid: Citric acid is usually made either from corn (most likely genetically-modified corn) or through a fermentation process using the fungus Aspergillus. I recommend avoiding citric acid mostly because the substrates used to make it (corn and mold) can irritate some people.
  • Maltodextrin: Maltodextrin is a heavily processed carbohydrate derived from corn, wheat, rice, or potato starch frequently added to processed foods. It triggers gut dysbiosis and inflammation and may impact mast cells through these mechanisms.
  • Xanthan Gum, guar gum, gellan gum, etc.: These ingredients are commonly used as emulsifiers, stabilizers, and binders in processed foods. They frequently appear in dairy alternatives such as almond, coconut, and oat milk. These gums may trigger digestive distress in sensitive individuals (which describes most individuals with MCAS!) I recommend steering clear of them as much as you can. Three Trees Original Almond Milk is the cleanest and most MCAS-friendly almond milk I’ve found; it contains just two ingredients, organic almonds, and filtered water. Native Forest Simple Organic Unsweetened Coconut Milk is my preferred coconut milk brand for people with MCAS and sensitive digestive systems.
  • Food colorings: Artificial food colorings such as “Blue 1” and “Red 40” demonstrate numerous detrimental health effects, including potential neurotoxic effects in children. (27) However, artificial food colorings may also increase histamine levels, causing problems for people with MCAS who already run high histamine. (28) Interestingly, children with variants (polymorphisms) in genes involved in histamine degradation appear to have more significant adverse responses to artificial food dyes. (29) This makes me wonder whether people with MCAS, who are already at a disadvantage due to heightened histamine levels, may be susceptible to artificial food colorings.
  • Smoke Flavoring: Smoke flavoring is produced through a wood-burning process called “pyrolysis.” (30) Anecdotally, I’ve found it to be a trigger for some of my clients with MCAS.
  • Yeast Extract: Fungal microorganisms can trigger mast cell activation (31), so it seems possible to me that yeast extracts (like nutritional yeast) could trigger MCAS symptoms. In fact, zymosan, a beta-glucan found in Saccharomyces cerevisiae (the type of yeast that comprises nutritional yeast), has been found to exert inflammation and increase mast cell activity. (32)
  • Other additives that I suspect may trigger MCAS symptoms include potassium sorbate, sodium triphosphate, potassium triphosphate, and sodium nitrate.

almond milk in the mast cell activation syndrome diet
Many brands of pre-made almond milk contain emulsifiers, such as xanthan gum and gellan gum, which may trigger a mast cell reaction.

Work with a Nutritionist to Identify Reactions to Other Foods

Besides histamine, people with MCAS can sometimes be reactive to other food components, including oxalates, salicylates, and lectins. If you’re dealing with multiple food sensitivities and MCAS, you need to tread carefully because all too often, I see people with MCAS and multiple food sensitivities remove a TON of foods from their diets, resulting in malnutrition and even adverse changes in the gut microbiome.

If you suspect you’re dealing with multiple food sensitivities, I strongly recommend that you work with a nutritionist who is well-versed in MCAS to figure out how to navigate your sensitivities (and ultimately recover from those sensitivities and expand your diet!) while still maintaining a nutrient-dense, healing diet. I regularly help clients with MCAS and multiple food sensitivities in my functional nutrition practice. If you’re interested in working together, you can schedule a discovery call with me to learn more about how I can help you!

Keep a Food Journal

Parsing out your body’s reactions to foods can be difficult when you have MCAS. This is why I often recommend that clients keep a food journal so they can make note of their responses to various foods. As long as the food journal doesn’t trigger anxiety around food, it can be a helpful tool for piecing together your ideal healing diet.

FAQ for the Mast Cell Activation Syndrome Diet

  1. Are eggs low-histamine?
    • In my experience, eggs elicit a histamine response for some people with MCAS but are fine for others. I consider eggs a “gray area” food for MCAS. If you’re eating a lot of eggs and experiencing MCAS symptoms, you may want to try removing eggs for a couple of weeks and then reintroduce them to see how your body responds.
  2. Are nuts allowed on the MCAS diet?
    • Of course, if you’re allergic to tree nuts, they’re off-limits on the MCAS diet. Some people also have IgG food sensitivities to certain nuts, like almonds, and experience inflammation when they eat them. These situations aside, I’ve found that certain nuts are particularly well tolerated on the mast cell activation syndrome diet, including macadamia nuts, pistachios, pecans, and almonds. Avoid nuts roasted in industrial seed oils, such as canola and safflower oil, as these oils are very inflammatory. I’ve also found that many people with MCAS tolerate soaked and dehydrated or sprouted nuts and seeds better than unsoaked/unsprouted nuts and seeds. The soaking and sprouting processes reduce antinutrients in nuts and seeds that can hinder digestion. By lowering levels of these compounds, we may improve digestive tolerance for nuts and seeds.
  3. Can I eat fish on the MCAS diet?
    • Yes, absolutely! In fact, the omega-3 fatty acids found in fatty cold-water fish, like salmon and halibut, may be vital for regulating mast cell activity inside the body. (ref) You’ll need to avoid canned and smoked fish if you are histamine-sensitive. I recommend purchasing flash-frozen wild-caught seafood. The flash-freezing process preserves freshness and may reduce histamine accumulation in the fish.
  4. Can I eat out on the MCAS diet?
    • It depends. I find that most people can eat out occasionally on the MCAS diet and see improvement in their symptoms as long as they choose anti-inflammatory foods when they eat out, like fish, steak, roasted vegetables, eggs, salads, etc. If you have restaurants near you that offer whole-food, organic, or gluten-free options, that may be your best bet for eating out. However, if eating out involves drinking a lot of alcohol and eating fried foods or foods laden with processed carbs, sugars, and industrial seed oils, then that will most likely not be supportive of your MCAS recovery process; at some point, eating those less optimal foods may be tolerable for your body, but I recommend focusing on healing for a while first before pushing the limits of your body’s tolerance with processed restaurant foods and alcohol.

The mast cell activation syndrome diet is a powerful tool that can support your MCAS recovery as a part of your overall treatment approach. If you need more help customizing your MCAS diet and putting it into action (including personalized meal plans!), I’d love to work with you in my functional nutrition practice! You can schedule a discovery call with me to learn more about how we can work together!

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