Almost 1 in 5 people worldwide live with food intolerance, leading to daily struggles like bloating, tiredness, and stomach upsets which can lower life quality (Nutrients, 2019). Also, they might cause long-term inflammation. Food intolerance can cause more problems with digestion and how much someone reacts can vary. If not managed properly, food intolerance can make conditions worse. These conditions include IBS (Irritable Bowel Syndrome), IBD (Inflammatory Bowel Disease) and whole-body inflammation. This inflammation can lead to issues with the heart and brain function. 

At Sanna Life Health, we apply Kinesiology to assist in the detection of food intolerance — a natural and customized method of realizing how food interacts with your body. By providing this method, we ensure you receive a deeper understanding of your health, so you can improve faster and avoid long-term problems.

This guide will help you get a deeper understanding of food intolerance. It will also explain the cause, the signs to look for and ways to manage them based on science. This guide includes info from great sources like The Healthy Eating Hub and experts like Dr. Will Cole, the Cleveland clinic and Hardvard medical school. With a combination of science, expert advice, and useful tips, this blog will help you. You will be able to identify what foods trigger your body, how to lower inflammation and improve your overall health with confidence.

What Are Food Intolerance?

Food allergies trigger the immune system, causing immediate and severe reactions. They can be diagnosed through blood tests or skin prick tests, while food intolerance, which disrupt digestion, are harder to pinpoint, often linked to enzyme deficiencies, gut imbalances, or food additives. With ultra-processed diets on the rise, our microbiome struggles to adapt, making intolerance more common than ever.



Yet, many doctors overlook them, as standard medical testing doesn’t fully recognize or explain food intolerance. Lots of people suffer unnecessarily with digestion issues.

Why they’re trickier to spot

Unlike allergies, intolerance often have delayed symptoms (hours later or even the next few days), making them harder to pinpoint. The severity also varies based on quantity, small amounts might be tolerable, while larger doses trigger symptoms.

Food Intolerance vs Food Allergies

The Healthy Eating Hub highlights key distinctions between food intolerance and allergies, which are critical for proper management:

Source: The Healthy Eating Hub, informedhealth.org (IQWiG)

For instance, let's take lactose intolerance. If you can't make enough lactase enzymes, lactose in your food won't digest well. It stays in your gut and ferments, giving you bloat and diarrhea. On the other hand, some people are allergic to the protein in milk, which is a different problem. Their immune system reacts and they might get hives or find it hard to breathe. 

Knowing which issue a person is needed help in handling it better. If you're lactose intolerant, maybe you can still have a little bit of dairy or foods that don't have lactose. But if you have a milk allergy, you just need to avoid anything with dairy for sure.

What Causes of Food Intolerance

Many things could lead to food intolerance, for example, enzyme deficiencies, problems with gut health (such as leaky gut), or elements from the environment. The Healthy Eating Hub and experts, such as Professor Sauid Ishaq who studies stomach health at the University of Birmingham, points out a few reasons, all backed up by science: 

Enzyme Deficiencies:

Lactose Intolerance: If your body doesn't have enough of a certain enzyme called lactase, it can make it hard to digest lactose, a kind of sugar. This problem affects around 68 of every 100 people in the world, according to the National Institute of Diabetes and Digestive and Kidney Diseases, or NIDDK for short.

Histamine Intolerance: Imagine a case where your body doesn't have enough of the diamine oxidase (DAO) enzyme. It's a chemical messenger (neurotransmitter) made by your immune system. So you might end up suffering from a typical histamine response which could include: Runny nose, hives, sneezing (like hay fever)

Headaches or migraines

Flushing, itching

Gut issues (bloating, diarrhea, nausea)

Anxiety or sleep disturbances and one that I see in my practice often is a swollen eye for no apparent reason, or a swollen cheek.

Irritable Bowel Syndrome (IBS):

IBS, or irritable bowel syndrome, often causes confusion about which foods might upset someone's stomach. This is frequently because the person's gut bacteria are making too many gasses. A study from 2015, published in the journal Alimentary Pharmacology & Therapeutics, found out that this is a common issue for people with IBS. They often feel unwell after eating certain foods.

Sensitivity to Food Chemicals:

There are several foods that naturally have organic compounds like salicylates (in fruits) or caffeine that can cause adverse reactions in some people.  And then there are the synthetically made ingredients like MSG and sulfites.  According to a study published in Nutrients in 2019, these chemicals can cause sensitivities even if they are not affecting the immune system and hold a substantial role for food intolerance.

According to The Healthy Eating Hub, some people can only tolerate a certain amount of these chemicals before kicking up trouble. If they exceed that limit then they may be between things like migraines and skin glitches.

Gut Dysbiosis and Leaky Gut:

Imbalances in gut microbiota or increased intestinal permeability (comment, which colloquially would be called, “leaky gut”) increase food sensitivities. Nutrients (2019) examined gut dysbiosis and found links with both IBS and food intolerance.

Potential toxin exposure from environmental chemicals like bisphenol A (BPA) can lessen gut barrier integrity and increase risk of intolerance (Environmental Health Perspectives, 2014).

Stress and Psychological Factors:

Long-term stress can interfere with gut motility and microbiota, worsening symptoms. The Healthy Eating Hub and the Heart Research Institute UK caution that the digestive tract is very responsive to psychological stress.

Genetic and Dietary Factors:

Genetic disorders like mutations in sucrase-isomaltase (everybody eats starch and sugar) disrupt starch and sugar digestion, per a 2018 study published in Gastroenterology.

Dietary patterns high in processed foods and low in fiber may also disrupt our gut microbiota and lead to increased intolerance-related diseases.

Lectins:

Lectins are naturally occurring proteins found in many plant foods, including beans, lentils, whole grains, and nightshades like tomatoes and peppers. While they serve as a natural defense system for plants, in some people—especially those with gut sensitivities or autoimmune conditions—lectins can irritate the digestive lining, contribute to bloating, and may even increase intestinal permeability (often referred to as “leaky gut”).

Proper preparation like soaking, cooking, or fermentation can reduce lectin content significantly, making these foods more digestible. But for individuals struggling with gut issues, temporarily reducing high-lectin foods may support healing and reduce inflammation.

As Dr. Steven R. Gundry discusses in his book, The Plant Paradox, lectins can be problematic for some individuals and should be approached with caution.

Common Foods Linked to Intolerance

Certain foods and compounds are frequent culprits. The Healthy Eating Hub highlights the following:

 Glyphosate Residues in Common Foods:

Another often-overlooked contributor to gut issues is glyphosate, a widely used herbicide commonly sprayed on crops like wheat, corn, and soy. Residues of glyphosate are frequently found in everyday foods such as non-organic bread, breakfast cereals, and snack bars. Glyphosate acts as a broad-spectrum antibiotic, meaning it doesn’t just target harmful microbes—it can also disrupt the balance of the gut microbiome by killing off beneficial bacteria. This microbial imbalance may contribute to increased gut permeability (“leaky gut”), inflammation, and food intolerance in sensitive individuals.

A review published in Interdisciplinary Toxicology highlights how glyphosate exposure can negatively affect gut bacteria, particularly by reducing populations of beneficial strains such as Lactobacillus and Bifidobacteria, while allowing potentially harmful species to flourish (Shehata et al., 2013)

FODMAPS:

FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols) are carbohydrates present in foods such as wheat, onions, apples, and dairy. In some people, FODMAPs are poorly absorbed which allows gut bacteria to ferment them and lead to symptoms of bloating.

The low-FODMAP diet is the gold standard for managing irritable bowel syndrome (IBS) and FODMAP-related intolerance and has been developed by Monash University (Nutrients, 2019).

Gluten-Containing Foods:

Celiac disease is an autoimmune condition where ingesting gluten causes the immune system to attack the small intestine, leading to damage and nutrient malabsorption.

Gluten intolerance (or non-celiac gluten sensitivity) doesn’t involve an autoimmune response or intestinal damage, but can cause symptoms like bloating, fatigue, and brain fog after eating gluten. 

When small amounts of gluten are tolerated, but then lead to symptoms in greater amounts, fructans are implicated.

Fructans are the carbohydrate (fiber) in foods such as wheat, onions, garlic, and some fruits. They are not completely broken down in the small intestine in the body, and rather, they ferment in the colon to produce gases. The fermentation causes the individual with sensitivities such as irritable bowel syndrome (IBS) to experience digestive distress such as bloating, gas, and cramps. Limiting fructan consumption might reduce such symptoms in sensitive individuals.

Food Chemicals:

Natural chemicals (e.g., salicylates, amines) and additives (e.g., MSG, artificial colors), can trigger adverse reactions in sensitive individuals. 

Lactose and Fructose:

Lactose in dairy and fructose in  fruit or sweeteners are common triggers for individuals with deficiency of enzymes to digest these substances or malabsorption issues.

Symptoms of Food Intolerance

Food intolerance symptoms don't necessarily present immediately. Sometimes these symptoms can come on gradually even 12 to 24 hours after eating a certain food. The symptoms of food intolerance usually affect the stomach and digestion, but can also affect symptoms outside the stomach such as in your skin, head, and energy.  If you regularly feel unwell after eating, or experience symptoms like bloating, headache, or fatigue for no known reason, food intolerance may be responsible.  Here are a list of common symptoms to be aware of:

Digestive Symptoms

• Bloating or gas – Stomach feels swollen or tight after meals.
• Stomach pain or cramps – Achy or sharp pain in the belly area.
• Diarrhea or constipation – Irregular or uncomfortable bowel movements.
• Fullness or discomfort – Feeling too full even after a small meal.
• Nausea – Uneasy feeling in stomach, may also lead to vomiting. 

Extraintestinal Symptoms

• Headaches or migraines - Ongoing discomfort in the head and possibly intense.
• Fatigue - Above average tiredness or feeling drained of all energy.
• Itchy or red skin - Rashes, hives, other skin irritation without knowing why.
• Joint pain - Unexplained aches or stiffness in joints.
• Brain fog - Difficulty concentrating, memory issues, or just a tired mind.

Emotional & Behavioral Symptoms

• Mood swings – Rapidly changing moods for no clear reason.
• Anxiety/irritability – Excessive restlessness, nervousness, or irritability.
• Sleep disturbances – Difficulties getting to sleep, or staying asleep.
• Hyperactivity (particularly in kids) – Excess energy, unable to focus, avoidant or acting out.
  
   

How Food Intolerance Contribute to Inflammation

The role of chronic inflammation in a number of disease processes, such as cardiovascular disease, diabetes, and decreased cognitive function, is well documented (StatPearls, 2023). Food intolerance contribute to the inflammatory process via the following means:

Gut Irritation: Undigested foods or other irritating agents compromise the gut barrier and increase gut permeability, known as "leaky gut", allowing inflammatory molecules to be released into the bloodstream.

Microbiome Imbalance: Trigger foods, such as high-FODMAPs (Fermentable Oligosaccharides, Disaccharides, Monosaccharides, and Polyols.), affect beneficial gut bacteria and decrease the anti-inflammatory short-chain fatty acids (SCFAs). A 2019 Nutrients study cautions that long-term low-FODMAP diets have the potential to reduce SCFA-producing bacteria. Careful, thoughtful use of the low-FODMAP diet can help offset potential adverse effects of trigger food consumption.

Low-Grade Immune Activation: Chronic exposure to trigger foods can stimulate low-grade immune responses, exacerbating conditions like eczema or migraines, per Dr. Will Cole.

Systemic Effects: Inflammation from intolerance increases the risk of IBS, GERD, and IBD. A 2023 Health.com article links lactose intolerance to GERD symptoms. Managing intolerance reduces gut irritation, restores microbiome balance, and lowers systemic inflammation, improving overall health.

Diagnosis of Food Intolerance

Diagnosing food intolerance is challenging due to delayed symptoms and lack of reliable biomarkers. The Healthy Eating Hub advises against self-diagnosis, as symptoms in the lower digestive tract (large intestine) reflect foods eaten 12–24 hours earlier, not the most recent meal. Evidence-based diagnostic methods include:

Food and Symptom Diary

Record meals, portion sizes, and symptoms for 2-4 weeks to identify patterns. The Cleveland Clinic recommends this as a first step.

Elimination Diet: According to the University of Wisconsin-Madison School of Medicine, the "gold standard" is to eliminate suspect foods for a period of 2–4 weeks, then working closely with a professional, to reintroduce them stepwise to identify and confirm triggers. An example of this is the FODMAPS diet, which is clinically recommended by the UK's National Institute for Health and Care Excellence (NICE) and phases of identification include restriction, re-challenge and maintenance.

Specific Tests:
Hydrogen Breath Test: Diagnostic test Measures levels of hydrogen in breath after consumption of test solution to assess lactose intolerance or fructose malabsorption.

Genetic Testing: Genetic testing is used to determine enzyme deficiencies (such as sucrase-isomaltase variants), but it has limited clinical utility in the diagnosis of carbohydrate malabsorption.

Professional Consultation

A registered dietitian or gastroenterologist will guide diagnosis based on evidence gathered from food diaries, and elimination diets. The Healthy Eating Hub will aim to create a structure that will limit unnecessary restrictions of food and maximize food variability.

Treatment and Management Strategies

Food intolerance cannot be resolved however you can manage your symptoms with dietary changes, lifestyle changes and treatment. Here are the reviews of best evidence based recommendations based on The Healthy Eating Hub and other credible sources.

Dietary Modifications

Elimination and Reintroduction: Decide which trigger foods to avoid completely. Avoid any triggers for 2 to 4 weeks. Then challenge each food one at a time with an interval of 3 to 5 days between foods to see any toleration. The Healthy Eating Hub have resources to help with working with the dietitian any remaining nutritional deficiencies.

Example: Lactose intolerant individuals may tolerate dairy (hard cheeses) or lactose-free products in limited quantities.

Low-FODMAP Diet: Nutrients, this diet limits fermentable carbohydrates, which can have a role in IBS and FODMAP-related intolerance the diet includes:

Restriction phase (2 - 8 weeks): high-FODMAP foods, such as wheat, onions and apples to reduce consumption.

Re-challenge phase: introduces foods back into the diet to identify specific triggers.

Maintenance phase: personalize the diet to reduce symptoms to the lowest level while maximizing food variety.

A dietitian will monitor nutrition adequacy and ensure the diet does not lead to excessive reductions in calcium or fiber over the long term.

Anti-Inflammatory Diets: The Mediterranean diet, and its emphasis on vegetables, fruit, nuts, fish, and olive oil consumption, should play a role in reducing inflammation and promoting gut health. The PREDIMED study (2013) reported that the associated weight loss improved cognition and reduced cardiovascular risk factors.

The Healthy Eating Hub outlined eating holistically, increasing fibre intake, and decreasing processed foods which normally contain sugar, fat, and salt.

Diverse Plant-Based Foods: Stephen Ward (2022) - Nutritional therapist has presented a case for dietary diversity to optimise gut microbiota. The intake of a variety of vegetables and berries increases production of Short Chain Fatty Acids (SCFA) to reduce inflammation.

Enzyme Supplements

Lactase supplements will offer assistance with the digestion of lactose. A study conducted in 2023 showed that taking an enzyme supplement did reduce symptoms in people with non-celiac gluten sensitivity.

DAO supplements may be helpful in cases of histamine intolerance, although the evidence is limited. I recommend you consult with a health care provider.

Gut Health Optimization

Probiotics: A systematic review in the PMC in 2021 demonstrated that probiotics with different strains improved symptoms of lactose intolerance by improving gut microbiota.

Fiber: Gradually increase fiber from low-FODMAP foods (including carrots and rice) to help increase the number of gut bacteria. The Healthy Eating Hub states that meeting your daily fiber requirements may also relieve some gut symptoms.

Address Dysbiosis: Functional medicine practitioners can help identify and treat bacterial overgrowth or imbalance of yeasts.

Stress Management

Stress exacerbates symptoms by changing gut motility. The Healthy Eating Hub and Heart Research Institute UK advocate for mindfulness, yoga, or movement to enhance digestive health.

Symptom Relief

There are over-the-counter medications such as antacids (Tums), anti-diarrheals (Pepto-Bismol), and anti-gas pills (Beano) that may aid symptoms. 

Antihistamines may help for histamine intolerance but should always be discussed with your general practitioner or healthcare professional.

Professional Guidance

A dietitian takes care of a balanced diet while avoiding triggers. The Healthy Eating Hub explains their responsibility in maintaining variety in the diet, an important predictor of long-term health.

Long-Term Benefits of Managing Food Intolerance

Effective management yields significant benefits:

Reduced Inflammation: Following strict avoidance of trigger foods and strict adherence to anti-inflammatory diets decreases systemic inflammation which reduces risk of chronic disease (StatPearls, 2023).

Improved Gut Health: Rebalance the microbiome and regulate digestion and nutrient absorption (PMC, 2021).

Enhanced Quality of Life: Alleviating symptoms will improve energy, diminish bad moods, and boost functioning in day-to-day activities.

Lower Risk of Complications: Lower Risk of Complications: Careful management of intolerance will lessen IBS, GERD, and eczema flare-ups.

Practical Tips for Living with Food Intolerance

Read Labels: Study the ingredients of your packaged food items for hidden triggers like lactose, wheat, or additives. When eating unpackaged food, ask what ingredients are in it.

Cook at Home: When cooking for yourself, you have control of the ingredient used and can fully mitigate accidentally being exposed to your food intolerance.

Stay Hydrated: The Healthy Eating Hub indicates that drinking enough water will aid digestion and reduce symptoms.

Join Support Groups: Support, both practical tips and emotional support, can be found on various online and public forums.

Monitor Nutrients: Dieticians can help you monitor whether you are getting enough fiber, calcium, and B vitamins, especially when avoiding the dairy and gluten food groups.

Final Thought

Food intolerance, although not life-threatening, can result in unpleasant symptoms and can contribute to chronic inflammation if left unaddressed. However, with education on the underlying factors, knowledge of the symptoms, and evidence-based recommendations that include elimination diets, low-FODMAP diets, and anti-inflammatory eating, both the symptoms can be reduced, therefore leading to improved physical health. Hearing from dietitians and specialists such as gastroenterologists will ensure you will be using a safe and tailored approach that incorporates variety into the diet and avoids deficiencies.