12 Of The Most Common Food Intolerances

A “one-size-fits-all” diet would be nice, but some people experience allergies or intolerances to foods that are both common and healthy.

A food allergy is a harmful — sometimes fatal — health effect caused by the immune system's response to a specific food (1). On the other hand, food intolerance is a nonimmune response to a specific food from the body, which is never life-threatening.

There are a handful of foods that are problematic for most people. Let’s take a look at some of the common food intolerances that I see the most often in my telehealth functional medicine clinic.

1. Dairy

Lactose intolerance is one of the most common food intolerances out there. Lactose intolerance occurs when your body cannot digest lactose, a sugar in milk and dairy products. (2) This inability to digest lactose is called lactose malabsorption. A lack of lactase enzymes in the body causes this inability to digest lactose. (3)

Now, some people can consume more lactose than others, but some cannot have dairy or lactose in any form. Lactose intolerance causes digestive symptoms like bloating, diarrhea, and gas.

It is important to note that a milk allergy is very different from lactose intolerance. A milk allergy is an allergic reaction to casein and/or the other proteins in milk and dairy products. (4)

Since most dairy farm cows are given hormones & antibiotics, unclean living conditions, and bad feed, their milk is typically pasteurized (superheated), homogenized (blended), and fat is often removed. To make up for this processed product having so little nutrition, synthetic vitamins are added back into the milk in an attempt to simulate what was included in its whole-food form.

Organic dairy is better because it does not allow hormones and antibiotics. Fermented dairy, such as grass-fed kefir and yogurt, is even better, as it mitigates some of the problems people have with casein sensitivity. It also includes beneficial bacteria, which is why it may be better tolerated.

2. Gluten

Gluten – the protein that’s found in grains like wheat, rye, and barley – is another one of the most common food sensitivities that I see.

To understand gluten intolerance, we need to understand autoimmune conditions. Many people think when we talk about gluten intolerance, we are referring to the autoimmune condition celiac disease. Yes, celiac is an autoimmune disease, but it is the extreme end of a broader gluten-intolerance spectrum. (5)

Related: The Negative Effects Of Gluten + The Best Way To Go Gluten-Free

You can be on the autoimmune-inflammation spectrum without having celiac disease, and that can result in gluten intolerance or non-celiac gluten sensitivity (NCGS). You may not have tests that come back saying you have an autoimmune disease, but I believe that gluten reactivity is a warning you could eventually be headed in that direction if you don’t change your diet and health habits.

Interested in taking action for your autoimmune condition? Check out my video course on Mastering Autoimmune Conditions & Inflammation With Functional Medicine.

Those who avoid gluten but still have symptoms may be grain-intolerant, even when those grains are gluten-free. You can have a sensitivity to any particular grain or all grains.

Cross-reactivity occurs when the proteins in grains such as rice and corn are similar enough in structure to gluten that the body mistakes them and reacts as if they were gluten. Many of my patients have sensitivities to some gluten-free grains, although not all.

Some cross-reactive foods include:

• Gluten-free grains
• Milk and dairy products
• Soy
• Coffee
• Chocolate
• Eggs

3. FODMAPs

FODMAPs stands for Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols. In short: fermentable sugars. These short-chain sugars are contained in many different foods and are not fully digested in the gut, which can cause them to be excessively fermented by gut bacteria.

This fermentation releases hydrogen gas that could lead to distension of the intestines, which can cause uncomfortable irritable bowel syndrome (IBS) symptoms in some people, such as pain, gas, bloating, constipation, and diarrhea. This FODMAP intolerance tends to be related to functional issues like small intestinal bacterial overgrowth (SIBO).

Most of the high-FODMAP foods are actually healthy, whole foods. Again, though, that doesn’t mean they work well for everyone. If you think you are FODMAP intolerant, try avoiding or severely limiting the following foods – at least temporarily – to see if it helps:

• Vegetables: Artichokes, asparagus, beetroot, celery, garlic, onions, leek bulb, legumes, Savoy cabbage, sugar snap peas, sweet corn
• Fruits: Apples, mango, nectarines, peaches, pears, plums, watermelon
• Dairy: Milk, cream, custard, ice cream, soft cheeses, yogurt
• Grains: Rye, wheat-containing breads, cereals, crackers, pasta
• Nuts: Cashews, pistachios

The goal of treating a FODMAP intolerance is not to remove the trigger foods forever but to heal the gut so you can eventually increase your intake of these particular foods. This is especially true when it comes to high-FODMAP fruits and vegetables, which are valuable sources of nutrients

Listen: How FODMAP Intolerance & SIBO Hurt Our Mood & Gut Health + What To Do About It

4. Fructose

Fructose, a FODMAP sugar, is one of the more common intolerances. Fructose intolerance is where the body lacks the enzymes needed to breakdown fructose. (6) This causes a build up of fructose, which is toxic to the liver.

5. Histamine

A histamine intolerance is when your body cannot produce enough enzymes to break down histamines or it produces too many. Your body releases histamines naturally in response to allergens. Many foods contain histamines or cause a release of more in your body.

Histamine intolerance is like an allergic reaction but without the allergen. The symptoms of this intolerance are similar to those of other allergic reactions (e.g. runny nose, nausea, headache, fatigue, etc.).

Learn more: Histamine Intolerance: Causes, Symptoms, and Natural Treatments

6. Eggs

Eggs have so many nutrients, mainly in the yolk, but that doesn’t mean this food isn’t problematic for some people. In my experience, it is actually the egg white that is typically more immunoreactive for people.

Ovalbumin, a protein in the white, is one of the most common allergens. (7) The yolks are generally better tolerated, although it’s important to note that some people can’t handle the yolk, either.

7. Nuts And Seeds

If you experience symptoms after consuming nuts or seeds, you may have a salicylate intolerance. Salicylate acid is a compound found in plants such as legumes and tree nuts (e.g. peanuts). (8) Many of the common symptoms of this intolerance are respiratory-related.

8. Caffeine

Caffeine sensitivity is when a person experiences stronger reactions to caffeine than most people, often due to genetic factors. (9) It can lead to symptoms such as restlessness, anxiety, rapid heartbeat, or insomnia – even with small amounts of caffeine.

The body's ability to metabolize caffeine varies, and those with higher sensitivity break it down more slowly, causing the effects to last longer. Reducing caffeine intake is an easy way to start managing this intolerance.

9. Alcohol

Regular consumption of alcohol can potentially negatively influence almost every system in your body. For the gastrointestinal system in particular, alcohol can be a trigger for leaky gut syndrome and gut inflammation in certain people.

People can also have an intolerance to the sulfites (food additives) found in beer, ciders, and wines. (10) This intolerance can cause asthma, skin rashes, or gastrointestinal distress. Sulfites may cause reactions by releasing sulfur dioxide that irritates the lungs and digestive tract. People with asthma or certain enzyme deficiencies are more susceptible to sulfite sensitivity.

10. Nightshades

A plant group that consists of tomatoes, peppers, potatoes, eggplant, goji berries, and some spices containing alkaloids, nightshades can be inflammatory for many people. These alkaloids act as a natural pesticide to keep bugs and mold away from the plants. The small amounts of alkaloids in the edible nightshades are not enough to harm humans.

However, specific people can be more sensitive to alkaloids and thus be intolerant to these foods. Nausea, vomiting, inflammation, brain fog, migraines, acne, rashes, hives, and achy joints after eating nightshades are all signs and symptoms of this type of sensitivity.

11. Sugar

Sugar is the favorite food of more pathogenic gut bacteria that can cause many gastrointestinal problems. This means that when you eat sugar, you are feeding the bad gut bacteria so they can crowd out the good bacteria that actually support your gut and overall health.

An imbalance of bacteria in your gut can also lead to negative effects on your body’s metabolism and immune responses. (11) Overgrowth of bad (sugar-loving) bacteria can also cause inflammation, eventually leading to an autoimmune-inflammatory response.

Research shows that artificial sweeteners also decrease the good bacteria in the gut, which could also cause glucose intolerance and lead to diabetes. (12)

Read More: How To Heal Your Gut: A Complete Functional Medicine Guide To Restoring Microbiome Health

12. Shellfish

Reactions to shellfish are caused by the body not having the enzymes to break down the proteins in shellfish. (13) Shellfish reactions can be both an intolerance or an allergy. Additionally, people can have reactions to crustaceans (e.g. shrimp and crab) and/or mollusks (e.g. clams and scallops).

Symptoms that indicate you might be experiencing a shellfish sensitivity are mainly digestive-based and can include​ abdominal pain, bloating, nausea, vomiting, and diarrhea.

Symptoms To Watch For

Some of the most common symptoms of food intolerances include (2,6,9,10)

• Bloating
• Gas
• Abdominal pain
• Diarrhea
• Nausea
• Restlessness
• Nervousness or anxiety
• Rapid heart rate
• Insomnia
• Upset stomach
• Headaches
• Skin reactions (e.g. hives)
• Respiratory issues (e.g. asthma)
• Dizziness

Food Intolerance Testing

One of the most common ways of testing is an Immunoglobulin Test (IgG Test). This test is done by an at-home finger-prick test or a lab blood draw. The sample is then tested for IgG food or drink antibodies within the blood.

An elimination diet is another easy way to determine if you have an intolerance. Simply remove a certain food (or many) from your diet for a period of time and start to reintroduce the suspected trigger foods one at a time. Watch for reactions and signs of intolerance as you add back the foods you eliminated.

In gluten cross-reactive testing, you consume foods with proteins that are similar to gluten or that are cross-reactive with gluten.

Read More: Your Complete Functional Medicine Guide To At-Home Food Intolerance Testing

Don’t Know Where To Start? We Can Help

If you have witnessed any symptoms or think you may have a food intolerance, we can help you determine exactly what foods could be the cause. We aim to provide an individualized approach for you and your unique symptoms and needs.

As one of the first functional medicine telehealth clinics in the world, we provide webcam health consultations for people around the globe.

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