Food intolerance – a digestive system response – and food allergies – an immune system response – are quite different from other adverse gut related conditions, such as food poisoning that results from spoiled or tainted food, which usually affects all people eating the same food.
Food allergies:
When an ingredient in food – usually a protein that the body is sensitive to – is detected and perceived as harmful to the body, an immune system response is triggered that creates a defence system in the form of IgE antibodies to fight it. While the antibodies fight the harmful invading protein, an allergic reaction occurs and results in symptoms such as a rash, nausea, stomach cramps or diarrhoea, itchy skin, chest pain, shortness of breath, or swelling of the airways to the lungs. A serious type of food allergy reaction called anaphylaxis can be fatal and results in a drop in blood pressure, loss of consciousness or even body system failure.
Food allergies occur each time the food is consumed and even small amounts trigger this immediate reaction. The most common food allergies result from peanuts, tree nuts, and shellfish. The immune cells producing the IgE antibodies have a memory and thus allergies are generally with you for the rest of your life, once you have reached adulthood.
Food intolerance:
While a food allergy is an immune system response, food intolerance is a digestive system response that occurs when an ingredient in the food irritates the digestive system, or when the digestive system is unable to properly digest the food.
Larger quantities of food are required to trigger the intolerance reaction and it takes longer, up to 48 hours, for the reaction to occur. For example, somebody with lactose intolerance may be able to drink milk in tea or coffee, but be affected by larger quantities of milk. Lactose intolerance from milk and other dairy products is the most common form of food intolerance.
Symptoms of food intolerance include stomach pain or cramps; gas; bloating; diarrhoea; vomiting, heartburn; nausea; headaches; migraines; runny nose; coughing; and irritability.
Causes of food intolerance:
- Lacking or having insufficient quantities of some of the enzymes in the digestive system that are needed to properly digest certain chemical compounds (proteins) in food.
- People with lactose intolerance do not have enough of the enzyme lactase that breaks down lactose (milk sugar) into smaller molecules. This results in the undigested lactose remaining in the digestive tract, with no absorption of the milk sugar.
- An intolerance to milk protein has similar symptoms to lactose intolerance, such as spasm, bloating, gas, diarrhea or stomach ache.
- Some of the chemical ingredients that are added to food – as preservatives; as artificial sweeteners; as emulsifiers; as colorants; or to enhance the taste – are often the source of food intolerance. A well-known cause of food intolerance is monosodium glutamate (MSG), a flavor enhancer.
- Grains that contain gluten are a common cause of food intolerance.
- Sulfites are substances that are added to food to prevent the growth of mold and occur naturally in red wine, and is often added to other wines.
- Some people are intolerant to food which can cause intestinal gas build-up, such as beans and cabbage.
- Some chemicals in food and drinks can cause food intolerance, such as amines in some cheeses and caffeine in coffee, tea, and chocolates.
- Processed meats contain nitrates and nitrites, which is a known cause of food intolerance in some people.
- Histamine in food can cause intolerance and occurs in cured food. It is also present in mushrooms and pickles.
- Some people may be intolerant to several types of food.
Prevention of food intolerance:
Food intolerance may have serious longterm consequences, such as neurological or immunological disorders, or conditions such as metabolic syndrome and chronic inflammation.
It is advisable to either avoid the food that triggers the intolerance symptoms, or to limit intake to the known amounts that the body can tolerate without any adverse effects.
Read food labels carefully to check the list of ingredients for any problem foods; remember to also check the ingredients of condiments and seasoning.
When eating out, notify the waiter about your known food intolerances and request them to check these with the chef. The menu usually does not list all the ingredients. When dining with friends, inform them well in advance of any intolerances.
Food intolerance and the gut:
Studies have shown notable differences in the intestinal bacteria between individuals with food allergies or intolerances, and non-allergic/intolerant individuals.
Intestinal bacteria are collectively known as the gut microbiota. Microbiota refers to the microbe population in a specific ecosystem, such as the populations found in the skin microbiota or the gut microbiota. (The term microbiome refers to the sum total of all microorganisms, as well as their genetic material, in or on their host). The gut microbiota are composed of diverse types of bacteria that break down (digest) food and interact with the mucosal immune system of the gastro intestinal tract (gut) in order to promote the immune tolerance of food.
A lack of diversity in intestinal bacteria may predispose individuals to certain food intolerances such as gluten intolerance. Certain species of gut bacteria assist with the breakdown of gluten proteins.
The numbers of beneficial bacteria in the gut can decrease due to lifestyle factors such as poor diet, chronic stress and lack of physical activities. This in turn can impair the immune tolerance in the gut, which contains an estimated 70 – 80% of the body’s immune system. The gut is the body’s largest contact area with the external world, with a larger surface area than the skin.
The inner lining of the gastro intestinal tract, which is in contact with food and the microbes that live in our gut, consists of a wall of cells that are tightly attached to each other. This creates a barrier that prevents gut microbes, and the toxins they can produce, from getting into the bloodstream. When certain ‘bad” microbes land up in the gut, the immune system reacts immediately to combat these microbes, resulting in inflammation in the gut wall. The immune attack and resulting inflammation can damage the cells that form this barrier and cause the cells of the barrier to become less tightly attached. The barrier can then be breached and become permeable to toxins and even the microbes that produce the toxins to cross this barrier into the bloodstream.
This condition is referred to as having a “leaky” gut and an increasing number of medical conditions (of which food intolerance is but one) have been linked to inflammation in the gut and the resulting “leaky” gut.
Food-induced activation of the immune system may initially be subtle, but can have serious consequences over time when local micro-inflammation in the intestinal tissue spreads insidiously and manifests in other tissues. This can affect the functioning of various systems in the body, such as the hormonal system, the nervous system and the immune system. This in turn may lead to complex symptoms that can manifest in various forms, making it difficult to identify food intolerance as the initial cause.
Apart from the main initial type of food intolerance, other intolerances may occur over time that result in multiple intolerances that can influence each other adversely.
Studies have shown that probiotics of human origin, which supplement the diversity of beneficial bacteria in the gut, may reduce permeability of the gut and, along with dietary modification, can be beneficial in the treatment of food intolerance.
Sources:
Food problems: Is it an allergy or intolerance? Published online and last reviewed 5 May 2015. The Cleveland Clinic. (www.clevelandclinic.org)
Food allergies and food intolerance. Published online and last reviewed 12 October 2017. WebMD. (www.webmd.com)
What is a food intolerance? Published online and updated 20 December 2017. Medical News Today. (www.medicalnewstoday.com)
The gut flora-food allergies connection. Published online 19 July 2017. The Kresser Institute. (www.kresserinstitute.com)
Inflammatory symptoms, immune system and food intolerance: One cause – many symptoms. Published online 29 July 2015. Cell Science Systems. (www.cellsciencesystems.com)
What is a leaky gut? Published in the March 2018 edition of the Harvard Health Letter. Harvard Medical School. (www.health.harvard.edu)
