Food Intolerance: Symptoms, Causes & Treatment

Food intolerance occurs when the body is unable to properly digest certain foods, which can cause symptoms such as abdominal pain, bloating, and excessive gas.

Some types of food intolerance include lactose intolerance, fructose intolerance, and gluten intolerance or sensitivity. This condition may occur due to the absence or reduced activity of digestive enzymes or because of intestinal conditions such as celiac disease and inflammatory bowel disease.

Treatment for food intolerance may be recommended by a gastroenterologist or registered dietitian and may include digestive enzymes, reducing or eliminating foods associated with the intolerance, and, in some cases, probiotic supplements.

Food intolerance symptoms

The main symptoms of food intolerance are:

• Abdominal pain

• Bloating

• Excessive gas

• Diarrhea or constipation

• Headache or migraine

• Excessive tiredness

• Nausea and vomiting

A person with food intolerance may also experience muscle or joint pain, red or itchy skin, and mood changes.

Food intolerance symptoms may appear within minutes or hours after eating the food and may be more likely or more severe when larger amounts are consumed.

Food allergy vs food intolerance

A food allergy is an immune system reaction to a specific substance in a food. According to the American Academy of Allergy, Asthma & Immunology, food allergy involves the immune system, while food intolerance typically involves the digestive system and does not carry a risk of anaphylaxis.

Food intolerance, on the other hand, occurs when the body has difficulty digesting or processing a particular food or food component, often causing gastrointestinal symptoms. It may not cause symptoms when only small amounts are consumed, as reactions can depend on the amount eaten and individual sensitivity.

Food intolerance test

To determine whether you have a food intolerance, you should consult a gastroenterologist or primary care provider, who will evaluate your symptoms and medical history.

The doctor may also recommend tests for conditions such as lactose intolerance or problems digesting certain carbohydrates, such as fructans, sucrose, or starch. An intestinal biopsy may be recommended when conditions such as celiac disease or certain intestinal enzyme deficiencies are suspected.

In some cases, the doctor may perform a food challenge, which involves consuming a suspected trigger food under appropriate medical guidance and monitoring for symptoms.

Main types

Different types of food intolerance or food sensitivity include:

• Lactose intolerance, involving lactose, a carbohydrate found in milk and dairy products

• Gluten intolerance or sensitivity, involving proteins found in grains such as wheat, rye, and barley

• Histamine intolerance, involving histamine, a substance naturally present in the body and found in varying amounts in foods such as processed meats, certain dried or preserved fish, wine, beer, vinegar, and aged cheese

• Intolerance to sucrose or certain starches, which may affect the digestion of foods containing these carbohydrates

• Fructose intolerance or malabsorption, involving fructose found naturally in fruits, honey, agave, and some vegetables

• Fructan intolerance or sensitivity, involving fructans found in foods such as wheat, rye, barley, cabbage, watermelon, apples, and leeks

• Raffinose sensitivity, involving a carbohydrate found in foods such as beans, onions, cabbage, nuts, and certain grains

Because food intolerance symptoms can be triggered by different foods, it is important to pay attention to what you eat and whether symptoms develop afterward.

Possible causes

Food intolerance is caused by difficulty digesting or processing a specific food or food component.

This difficulty may be related to reduced or absent digestive enzyme activity, genetic factors, or conditions that damage the intestines, such as celiac disease and inflammatory bowel disease.

Treatments options

Treatment depends on the specific type of food intolerance and may include:

• Reducing or avoiding foods associated with symptoms for the period recommended by a doctor or registered dietitian

• Taking lactase products before consuming milk products to help break down lactose and reduce the likelihood of symptoms, according to the National Institute of Diabetes and Digestive and Kidney Diseases

• Eating probiotic foods or using probiotic supplements if recommended by a doctor or registered dietitian

For certain carbohydrate intolerances or sensitivities, a registered dietitian or doctor may recommend a low-FODMAP diet. This diet temporarily restricts foods high in fermentable carbohydrates, including excess fructose, lactose, fructans, galacto-oligosaccharides, and polyols, followed by systematic reintroduction when appropriate.

It is also recommended to consult a registered dietitian so that an eating plan can be developed according to each person's nutritional needs.