Most of us have experienced unpleasant symptoms after a meal. When we’ve eaten too much or too quickly, some bloating and stomach pain is not unusual. However, when discomfort after meals becomes a regular occurrence, that’s often a sign of a food sensitivity. And digestive discomfort is just one of many signs.

What are food sensitivities?

Food sensitivities are distinct from food allergies and food intolerances, although many people use “sensitivity” and “intolerance” interchangeably.

Food allergies are classic allergic reactions to food. People with food allergies experience a severe immune response (known as an Immunoglobulin E or IgE reaction) when they eat certain foods. Food allergy reactions often include hives, facial swelling, difficulty breathing and they can be life-threatening.

Food intolerances are primarily a digestive issue. A food intolerance develops when a person is unable to process or digest certain foods. Digestion requires the right enzymes in sufficient amounts, and without them, poor digestion and discomfort result. The most common food intolerance is lactose intolerance, which results from a deficiency in lactase, the enzyme that processes a type of sugar called lactose found in dairy products.

Food sensitivities are reactions to foods that don’t meet the criteria of food intolerances or food allergies. For people with food sensitivities, research suggests that exposure to specific foods creates an Immunoglobulin G (IgG) reaction. While the presence of IgG antibodies is considered a normal response of the immune system to food exposure, studies have shown that IgG food hyperreactivity (i.e., production of IgG antibodies significantly above normal levels) is linked to systemic inflammation and disease. Food sensitivity reactions are mild to moderate, often delayed (up to 72 hours!) and can last longer than classic allergic reactions. Symptoms of food sensitivities are not life-threatening, but they can have a significant impact on daily functioning and quality of life. While some signs of food sensitivities are the kind we would expect (i.e., digestive symptoms), others are more difficult to trace back to food and therefore often overlooked.

What are the signs?

1) Digestive issues

The most obvious signs of food sensitivities are digestive symptoms. These include bloating, abdominal pain, gas, and constipation or diarrhea. These also happen to be the primary symptoms of irritable bowel syndrome (IBS). Studies involving IBS patients have found that eliminating foods based on IgG antibodies significantly reduces IBS symptoms and improves quality of life. Even if you’re experiencing milder digestive issues, identifying and addressing food sensitivities may be beneficial.

2) Headaches & migraines

Headaches are a fact of modern life, and the occasional mild to moderate headache is likely not a cause for concern. However, frequent headaches or more intense migraine headaches can be debilitating. Interestingly, up to 60% of patients report food as a trigger for migraines. Research supports this connection as well. Switching to a diet free of IgG-mediated “reactive” foods can significantly reduce migraine and headache symptoms for many people.

3) Brain fog

Brain fog is a somewhat nebulous term (pun intended!) used to describe symptoms such as poor concentration, memory problems, inability to focus, and fuzzy thinking. Given what we know about the impact of nutrition on the brain, a connection between food and brain fog isn’t surprising. In fact, brain fog is a documented symptom of non-celiac gluten sensitivity (NCGS), an immune-mediated food reaction. Food sensitivities have also been extensively studied in the context of ADHD. Restricted diets are effective in managing ADHD symptoms in a clinically meaningful subset of cases. While more research is needed, if you suspect that certain foods are making you “foggy”, this is definitely worth exploring.

4) Mood changes

The connection between food and mood is such a fascinating topic. While this link has now been well-documented by scientific studies, it’s still mostly ignored by mainstream medicine. A patient seeking guidance for a mood imbalance is unlikely to receive nutritional advice from their doctor. And yet, research points towards immune-inflammatory signaling activity in mood disorders with food sensitivity reactions implicated as a contributing factor. The link between food sensitivities, gastrointestinal issues, and depression is especially strong.

5) Skin problems

Food sensitivities frequently contribute to skin problems, such as acne, rashes, and eczema. Research supports diet as an important factor in these conditions. Once again, inflammation seems to be the root cause. To maintain healthy skin, an anti-inflammatory diet is key. Allergic reactions, including both food allergies and food sensitivities, are one of the earliest signs of inflammation and frequently show up on the skin first.

6) Fatigue

If you’re constantly tired, you may have a food sensitivity. Food sensitivities often lead to nutrient absorption issues and nutritional imbalances which can contribute to fatigue. In addition, research has linked chronic fatigue with IgG-mediated food sensitivities. While fatigue can have a number of causes, if you’re experiencing fatigue along with several other symptoms in this list, you may want to consider a dietary cause.

7) Sleep problems

How’s your sleep? Sleep has a definite link to inflammation. In fact, sleep disturbances can be both a cause — and a result — of dysregulated inflammatory responses in the body. Eliminating foods that cause IgG-mediated immune reactions has been shown to reduce sleep disturbances and improve sleep quality.

8) Joint pain

There is a growing body of research supporting a connection between joint pain and food sensitivities. In fact, this link is so strong that numerous studies now refer to it as the gut-joint axis. Immune-mediated food antibodies are significantly higher in people with with rheumatoid arthritis, a chronic inflammatory disorder that causes joint pain. Other research has shown that joint pain is prevalent in patients with food hypersensitivity. While anti-inflammatory medications are the most common treatment for joint pain, from a root cause perspective it may be more beneficial to consider reducing inflammation through dietary modifications.

9) Weight gain

Inflammation triggered by food sensitivities can lead to weight gain, and make it more difficult to lose weight. Obesity is associated with chronic low-grade inflammation, and immune-mediated food reactions can exacerbate this kind of inflammation. This creates a vicious cycle, as research also suggests that obesity can actually increase the risk of food allergies by causing an imbalance of allergic-related immune cells in adipose tissue, which in turn can damage the intestinal barrier.

10) Cold & flu-like symptoms

As we head into cold and flu season, it’s important to note that food sensitivities can actually cause symptoms such as coughing, sneezing, sore throat, and a stuffy or runny nose! In fact, in one study of food sensitivity reactions, nasal obstruction, sneezing, phlegm, and runny nose were among the most common symptoms. Of course, these symptoms are much more likely to indicate a cold or flu than a food sensitivity. However, if you have chronic nasal congestion or a cough that just won’t go away, you may be dealing with an immune-mediated food reaction.

Think you might have a food sensitivity?

The best way to identify food sensitivities is to do an elimination diet. This involves removing the most common allergenic foods (such as gluten, dairy, eggs, and others) for a specific period of time. After the elimination period, the next step is to reintroduce foods, one at a time, to gauge physical, mental, and mood-related reactions.

Of course, the goal is to have the least restrictive diet possible. While eliminating one food in exchange for significant symptom relief might be manageable, people with multiple food sensitivities are in a much more difficult spot. An individualized nutritional support plan that includes probiotics, enzymes, and other gut-healing supplements can make a significant difference. In time, as the gut heals and symptoms improve, many people find that they’re able to tolerate foods that previously caused problems for them.

While IgG food sensitivity testing is now widely available (including direct-to-consumer tests that can be done at home), these tests are not very reliable. A well-planned and carefully executed elimination diet is generally more accurate, cost-effective, and provides better insights. Check back for an elimination diet “how to” in a future blog post!