Introduction

The consumption of certain food types has led to adverse reactions in particular people. Cases of food tolerances and food allergy have been documented in 3.6% of the Western population, which has risen by 20-35% in the last 20 years. These reactions may cause individuals to develop eating disorders, dysbiosis, and experience a worse quality of life. Furthermore, most of these reactions are food intolerances, pharmacologic reactions, and toxic reactions, rather than allergic reactions.¹

Recent research findings from Clarie L. Jansson supported the associations between food intolerance and conditions like anxiety and depression with diminished health related quality of life (QoL). However, these adverse food reactions that are reported by individuals are treated via therapeutic interventions through self-diagnosis and not dietary or medical consultation.¹ 

What is food intolerance?

Food intolerance is when an individual has difficulty digesting certain food or ingredients in it. In other words, the gut is sensitive to certain foods and cannot tolerate them. Common symptoms associated with food intolerance are diarrhoea, abdominal pain, or gas. Sometimes food intolerance may also be referred to as food sensitivity.²

Food intolerance and food allergies: how similar are they?

Food intolerance and food allergy are not as similar as is often mistakenly believed. The table below compares how a lot of factors and characteristics differ between food intolerances and food allergies:.²

What causes food intolerance?

An enzyme deficiency is the cause of various food intolerances. The enzyme deficiency in the gut leads to symptoms like cramps, diarrhoea or bloating. The digestion of the carbohydrates in the food needs that specific enzyme which is missing.³

Food intolerance can also occur due to sensitivity to particular chemicals present in the food, rather than to the food itself. Furthermore, the cause of food tolerance can be due to irritable bowel syndrome (IBS). IBS is a chronic condition which leads to painful and annoying abdominal and bowel symptoms due to consuming particular foods.⁵ 

Which food causes food intolerance?

Lactose intolerance

This happens due to low levels of the enzyme lactase, which is required to break down the sugar found in cow’s milk for the digestive system. Furthermore, there may be gastrointestinal infection due to the reduction of the lactase enzyme levels. Other dairy products such as cheese and yoghurt have lactose in them.⁴

Gluten intolerance

The combination of rye, barley, and wheat protein is known as gluten. It is present in many common products such as pasta, cakes, biscuits, crackers and bread. In addition, many people with a gluten intolerance have to avoid oats as there is the possibility of contamination issues.⁴ 

Some individuals are required to be careful of food additives and food chemicals as there is a possibility of having a reaction from substances present in them and these including:⁴

Benzoates (Benzoic acid)

These are found in animals and made by various plants. They are also present in berries and milk. Foods such as chocolate, sweets, jams and soft drinks may have benzoates added to them.

Caffeine

Caffeine occurs naturally in plants and is used in tea, energy drinks, coffee, and chocolate. It is a popular stimulant.  

Alcohol (ethanol)

This is normally consumed in alcoholic drinks like spirits, wine, or beer. It is also an organic substance.

Salicylates

These are a naturally occurring groups of chemicals made by plants to fight off disease, bacteria, and insects. They are found in fruits, herbs, vegetables, and species of synthetic made salicylates are added to aspirin and other non-steroidal anti-inflammatory (NSAID) medicine.

Monosodium Glutamate (MSG) 

Found naturally and used in cured meats, ripening fruits and added to savoury food for seasoning. 

Sulphur dioxide (sulphites)

Sensitivity to sulphites most commonly impacts individuals with asthma, particularly those with severe steroid dependent asthma. It is found in beer, dried fruits, wine and beer.

Vaso active amines (including Histamine)                                                                           

Histamine is made via bacteria during fermentation, storage or decay. Foods that commonly contain histamine are vegetables, fruits, fermented soy products, green tea, cured meats, coffee, wine, beer, champagne and fresh fruit juice.

Sign and symptoms of food intolerance

Food intolerance symptoms are totally different for each person as the food they consume and amount they eat can lead to a particular reaction. However, if they consume small portions then there may be no symptoms but vice-versa if they consume large portions.⁵

Food intolerance symptoms may include the following:⁵

• Nausea
• Stomach pain or cramps
• Gas or bloating
• Vomiting
• Heartburn or acid reflux
• Diarrhoea
• Constipation
• Headaches, migraines
• Skin rash or flushed skin
• Hives
• Fatigue
• Irritability or nervousness (from caffeine intolerance)
• Anaemia

What are the complications of food intolerance?

The complications vary from individual to individual as food intolerances differ.

Individuals who are lactose intolerant will have deficiency in calcium and vitamin D if they eliminate dairy products completely. However, these individuals can take supplements to consume dairy products without getting an upset stomach, as well as to supplement their calcium and vitamin D intake.²  

Individuals who are gluten intolerant are required to consume more gluten free whole grains, fresh fruits and vegetables to obtain the required fiber and other nutrients such vitamin B in their diets. Elimination or reduction of foods containing gluten is often strongly recommended.² 

Diagnosis of food intolerances

Diagnosis of food intolerance can be complicated as the substances in food and quantity you consume will determine the severity of the symptoms such as bloating, diarrhoea, hives, rashes, headaches, stomach pain or gas, leading to highly individual reactions.⁶ 

To diagnose an adverse food reaction, a doctor will need to use the individual's clinical history, lab testing and information on their responses to medication. If someone is tested  for food tolerance via blood test or skin prick tests, the results may come back as a false negative as these tests are intended for food allergies as they are used to determine the presence of the antibodies (IgE) present following an allergic reaction, but not a food intolerance reaction. This test is helpful for individuals if they have a history of food allergy, however as this is different from food tolerance, this test is ineffective for people with food intolerances.⁶  

If symptoms occur such as mouth ulcers, recurrent IBS, migraine headaches and hives then it is time to visit a doctor to make a diagnosis. Furthermore, visiting a doctor can help to verify if other conditions or your dietary consumption is causing. These symptoms can be avoided if you and your doctor are able to identify what triggers them.⁶ 

Management of food tolerances via elimination diets

After the diagnosis is verified, the clinical history is crucial in helping identify the role of diet or other factors that cause food intolerances. The most effective way to determine if diet is the cause of food intolerance is by putting individuals on temporary elimination diets under the guidance of a dietitian and doctor. Removing certain foods from the diet can help individuals with intolerances to these specific foods. Following changes in their symptoms under controlled conditions can be helpful to find out which food triggers the adverse reactions, and elimination of this food may be required to avoid these symptoms from happening again.⁶

These elimination diets should be temporary with a short trial period, and carried out under strict medical supervision. As a diagnostic tool as the main goal is to find which food causes food tolerance. A prolonged elimination diet may cause nutritional deficiency, especially in children.⁶ 

Summary

Adverse reactions to food have become much more common in the Western population, now affecting 20-35% of people. Food intolerance affects the digestive system and is often self diagnosed. The causes of food tolerance are deficiencies of certain enzymes, sensitivity to certain chemicals found in food, and IBS. Food intolerances may cause issues such as depression, anxiety, and lower quality of life. The common symptoms of food intolerance are headaches, gas, bloating, diarrhoea, abdominal cramps and nausea. Moreover, intolerances to gluten, lactose and food additives are common. Diagnosis is also tricky and requires a doctor. Diagnosing food intolerance may require the individual to go on temporary elimination diets under medical supervision to find out which food is triggering their symptoms. Finding out which food is the cause and reducing or eliminating it form their diet may help to stop the discomfort and can vastly improve the quality of life of the affected individuals.