What Is Food Intolerance?
Medically reviewed by Jay N. Yepuri, MD
Food intolerance or sensitivity means you have difficulty digesting certain foods. Eating a food you are intolerant to can lead to symptoms like bloating, gas, abdominal pain, and diarrhea.
An estimated 20% of people worldwide live with food intolerance. Despite how common it is, food intolerance can be difficult to diagnose. No food intolerance test exists, so determining intolerances often requires time, patience, and careful observation.
A healthcare provider, such as an allergist or immunologist (a doctor who specializes in immune-related conditions), can help you identify triggering foods or ingredients and provide guidance on how to prevent and manage symptoms.
Food Allergy vs. Intolerance
A food intolerance is not the same as a food allergy. An allergy causes an immune reaction. The body produces Immunoglobulin E (IgE) antibodies in response to a particular food or food component.
Potential allergic reactions include hives, swelling, and difficulty breathing. These reactions can be life-threatening. They can be caused by touching or inhaling a particular food, as well as by eating it. The tiniest amount of food can result in a dangerous reaction. Reactions can be immediate or occur several hours later.
Food intolerances involve the digestive system, not the immune system. Some food intolerances, like lactose intolerance, are due to enzyme deficiencies. Other food intolerances involve sensitivity to food additives or components.
Though food intolerance symptoms can be incredibly uncomfortable, they are not life-threatening. Reactions generally begin about 30 minutes after consuming the food, but they might not occur until one or two days afterward.
Types
People can experience sensitivity to many foods, additives, and naturally occurring chemicals in foods. The most common types of food intolerance include lactose, gluten, and FODMAPs.
Lactose Intolerance
Lactose intolerance occurs when your body cannot properly digest lactose, a sugar found in dairy. This happens due to low levels of lactase—an enzyme produced by the small intestine that helps break down and digest lactose.
People with lactose intolerance may experience digestive discomfort after consuming dairy products like cheese, milk, or yogurt. Some people who are lactose tolerant can tolerate more lactase than others.
Lactose intolerance is relatively common. It affects about 30 million people in the United States by age 20. About 68% of people worldwide experience lactose malabsorption, which means they have difficulty digesting lactose. However, you're only considered lactose intolerant if you have symptoms.
Gluten Intolerance
Gluten, a protein found in wheat, barley, and rye, can trigger digestive discomfort and other symptoms in people who have a gluten sensitivity, or a non-celiac gluten sensitivity (NCGS). Symptoms are similar to those caused by celiac disease, an autoimmune disorder triggered by consuming gluten. However, unlike celiac disease, gluten sensitivity doesn't damage the small intestine.
Gluten intolerance symptoms also tend to appear more quickly than celiac disease symptoms, which generally appear at least one day after eating gluten.
FODMAP Intolerance
FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) are a group of carbohydrates, or sugars, that are not fully broken down before reaching the large intestine. Instead, they're fermented by gut bacteria when they reach the colon (large intestine). This slow digestion process can cause excess gas and water.
Irritable bowel syndrome (IBS) is a chronic condition that affects the gastrointestinal tract. People with IBS are often more sensitive to high-FODMAP foods, which include garlic, onions, beans and legumes, dairy, and fruits with pits like apples and cherries.
Food Intolerance Symptoms
Food intolerance can cause a wide range of symptoms. Symptoms can develop anywhere from 30 minutes to 48 hours after consuming the food you are intolerant to. Symptoms and their severity vary depending on the type and amount of the food consumed. For example, if you are lactose intolerant, drinking a small amount of milk may not trigger symptoms, but drinking larger amounts might.
Common symptoms of food intolerance include:
Bloating
Abdominal pain
Gas
Diarrhea
Causes
Genetics, digestive disorders, lack of digestive enzymes, and sensitivity to food additives all play a role in food intolerances. The specific cause depends on the type of food intolerance.
Lactose Intolerance Causes
Lactose intolerance is often genetic. It's more common in people with African, Asian, or Native American heritage.
Digestive disorders, infections in the small intestine, and surgery on the small intestine can also lead to lactose intolerance. Crohn's disease is a type of inflammatory bowel disease (IBD) that causes inflammation and discomfort in your digestive system.
Gluten Intolerance Causes
The exact cause of gluten intolerance, or NCGS, is not fully understood. Researchers exploring possible causes suggest that other compounds in wheat, such as fructans and amylase trypsin inhibitors, may cause sensitivity.
FODMAP Intolerance Causes
The causes of FODMAP intolerance are unclear, but it's more common in people with digestive disorders, like IBS. It's also more common in people with other food intolerances, including lactose intolerance.
Risk Factors
Certain factors can increase your risk of developing food intolerance, including:
Genetics: A family history of food intolerance, especially dairy or gluten intolerances, can increase the likelihood of developing food intolerance.
Premature birth: Infants born before 36 weeks might be lactose intolerant.
Late introduction of solid foods: Introducing solid foods to infants after seven months might increase the risk of food allergies and intolerances.
Underlying digestive disorders: People with digestive disorders like Crohn's disease or irritable bowel syndrome often have food intolerances.
Previous illness or injury: Illness or injury that affects the small intestine may increase the risk of certain food intolerances, such as lactose intolerance.
History of weight loss surgery: People with a history of weight loss surgery, such as gastric bypass, may experience food intolerances.
Food Intolerance Testing and Diagnosis
Very few diagnostic tests can help diagnose food intolerance. Identifying triggering foods often involves time, patience, and working with a healthcare provider.
Your healthcare provider will review your medical history and discuss your symptoms. They may recommend the following to pinpoint the cause of your discomfort:
Food diary: Keeping a detailed record of what you eat and any resulting symptoms can help reveal patterns and determine which foods cause reactions.
Elimination diet: This is a fundamental approach for investigating food intolerance. It involves removing suspected trigger foods from your diet for particular periods of time and monitoring whether or not your symptoms improve. You will then slowly reintroduce suspected trigger foods, one at a time, and monitor symptoms. This process takes several weeks.
Hydrogen breath test (BT): This test measures the amount of hydrogen in your breath after consuming specific foods containing sugars, such as fructose and lactose. This can help determine how well your body breaks down these sugars to identify food intolerances.
Related: How Are Allergies Diagnosed?
Treatment
There is no cure for food intolerance, so treatment focuses on preventing and managing symptoms. Dietary modifications and supplements are the most common treatment approaches. A healthcare provider can help tailor a treatment plan that fits your needs.
Dietary Modifications
Modifying your diet is the best way to manage food intolerance. This may involve eliminating or reducing your intake of foods or ingredients that trigger symptoms. Once you have identified foods that cause discomfort, avoiding or limiting your consumption can help prevent symptoms. For example, you could try lactose-free milk or gluten-free products.
Related: Dairy Elimination Diet: How to Start Cutting Out Dairy
Enzyme Supplements
Enzyme supplements can help improve digestion and reduce intolerance symptoms. For example, you can add lactase enzymes to milk or take them in tablet form. One small study of 30 people with non-celiac gluten sensitivity found a significant improvement in symptoms, as per a questionnaire, following a two-week regimen of enzymes.
Dietary supplements are minimally regulated by the FDA, and the effects depend on many variables, including type, dosage, frequency of use, and interactions with current medications. Always speak with your healthcare provider or pharmacist before starting any supplements.
Probiotics
Probiotic supplements contain beneficial bacteria that may help support gut health and relieve some gastrointestinal symptoms associated with food intolerance.
For example, in one small study of 104 people with IBS, people who took a probiotic supplement for four weeks had more gut Bifidobacterium (a group of probiotic bacteria) than people who did not take the supplement. People who follow a low FODMAP diet to reduce IBS symptoms might have fewer gut probiotics as a result of restricting foods rich in probiotics. Therefore, this research suggests that a supplement might help increase these lower probiotic levels in the gut.
More research is needed to determine the possible effects of specific types of probiotics on different food intolerances.
Related: What's The Difference Between a Probiotic and Prebiotic?
Prevention
While there is no guaranteed way to prevent food intolerance completely, you can reduce the frequency and severity of your symptoms. Here are some preventative steps you can take:
Portion control: Monitoring the amount of trigger foods you consume can help reduce the likelihood of symptoms.
Read food labels: Awareness of ingredients in foods you eat can help prevent unintended consumption of foods or ingredients that lead to digestive symptoms and discomfort.
Stress management: Chronic (long-term) stress can worsen food intolerance symptoms, so adopting stress-reduction techniques that work for you may be helpful. Stress reduction strategies include meditation, regular exercise, and limiting social media.
Related Conditions
Food intolerance can sometimes increase the likelihood of related conditions. Conditions associated with food intolerance include:
Irritable bowel syndrome (IBS): IBS often coexists with food intolerance, particularly FODMAP intolerance.
Inflammatory bowel disease (IBD): Some people with food intolerance, particularly gluten sensitivity, may have a slightly higher risk of developing IBD, including Crohn's disease and ulcerative colitis (a chronic inflammatory bowel disease that causes inflammation in your digestive tract).
Gastroesophageal reflux disease (GERD): Certain food intolerances, such as lactose intolerance, are linked to an increased likelihood of experiencing GERD symptoms like heartburn and chest pain.
Eczema: People with food intolerance are at an increased risk of eczema, an inflammatory skin condition that causes itchy, dry patches of skin.
Migraine and headaches: Certain food intolerances are linked to an increased risk of migraine and headaches.
Living With Food Intolerance
People generally have food intolerances their entire lives. Navigating life with food intolerance can be uncomfortable and frustrating at times, but you can manage symptoms and reduce the effects it has on your life. Adopting a mindful approach to eating can make a positive difference.
Ensuring you're getting adequate nutrients is important. A registered dietitian can help you create a balanced eating plan that meets your nutritional needs.
Connecting with other people who have food intolerances through online forums or support groups can provide a sense of community, valuable insights, and emotional support.
Frequently Asked Questions
What is the most common food intolerance?
Lactose intolerance is the most common food intolerance. An estimated 68% of people worldwide are lactose intolerant. About 36% of people in the United States live with lactose intolerance.
Can you be intolerant to something but not allergic?
Yes, it's possible to be intolerant to certain foods without having a true allergy. Food allergies involve the immune system's response. Intolerances are often related to difficulties digesting or absorbing certain foods or food components.
Can you develop a food intolerance later in life?
Yes, you can develop food intolerance later in life. Changes in gut health, enzyme levels, underlying health conditions, and other factors can make you intolerant to foods you previously tolerated well.
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