Allergies and Intolerances Relating to Gut Health
The digestive system is an amazing organisation of organs, which work together to break down and digest food, absorb nutrients, as well as produce certain nutrients like vitamin K, vitamin B12, serotonin and short-chain fatty acids. Within the large intestine we each house trillions of bacteria, the combination of microbes is unique to each of us and referred to as our ‘microbiome’. The diversity in strains of bacteria we each contain evolves in our early years of life and is defined through our environment, diet and lifestyle. This bacteria does much more than just exist in our bodies; it interacts, benefits, contributes and protects. To find out more about gut health, read on…
Allergies and Intolerances Relating to Gut Health
Worldwide, there is extensive research looking into the links between gut bacteria, health and different conditions and diseases. Links between gut health and allergy bring in the ‘hygiene’ hypothesis. This hypothesis argues that a lack of exposure to infection, beneficial bacteria (intestinal flora and probiotics) and parasites in the early years of life increases the susceptibility towards allergic disease. The thinking behind this is inadequate stimulation of certain immune system cells, helper T cell 1 (Th1), which are regulated in the gut.
A further link between allergy, intolerance and gut health is that of intestinal permeability. The intestinal wall is permeable to allow nutrients to pass into the bloodstream, however, it also needs to be impermeable to larger molecules, such as protein antigens or food particles that have not been adequately broken down in the digestive process. A reduction in the integrity of the intestinal wall and an increase in permeability, known as hyper-permeability can allow such particles to pass through. The body identifies these as ‘foreign invaders’ and produces antibodies in order to destroy the antigen and protect the body.
Different Types of Intolerances
There are different types of intolerances; immune-mediated intolerances and enzyme-mediated intolerances, there are additionally those which fit into neither category;
In immune-mediated intolerances larger particles can pass through the wall of the small intestinal lining. The body identifies these as ‘foreign invaders’ and produces IgG4 antibodies in order to destroy the antigen and protect the body.
Lactose intolerance is enzyme-mediated. The body cannot digest lactose, the sugar component found in dairy products, and so symptoms occur such as cramps, bloating, diarrhoea and vomiting. People who suffer from lactose intolerance do not produce enough of the enzyme lactase, and so the lactose is not absorbed properly in the small intestine.
A histamine intolerance or sensitivity is thought to be a build-up of histamine in the body due to an inability to adequately break it down due to an insufficiency of either diamine oxidase (DAO) and Histamine N-methyltransferase (HNMT) or both.
Caffeine is metabolised in the liver by the enzyme CYP1A2. Some people produce less of this enzyme and therefore metabolise and eliminate caffeine less efficiently than others.
In non-coeliac gluten sensitivity the symptoms experienced are very similar to those of coeliac disease and triggered by consuming gluten. However, in persons with NCGS the body does not attack and damage the small intestinal lining, characteristic of coeliac disease. The causes of this intolerance are not fully understood.
In fermentable oligo-, di-, and mono-saccharide and polyol (FODMAP) malabsorption certain carbohydrates can cause them irritation. The inability to break these food items down adequately means they can travel to the large intestine, where they are fermented by bacteria and can cause symptoms.
Enzymes are released in the stomach and work to break down the food so that when it enters the small intestine the body can begin to absorb the nutrients. Inadequate or deficient amounts of certain enzymes can lead to specific food groups not being readily available for absorption leading to physical symptoms, either because they pass through the small intestinal wall provoking an immune-mediated reaction and symptoms. Or because they reach the large intestine not adequately digested, which leads to fermentation and symptoms.
The removal of trigger foods can reduce inflammation and symptoms in a couple of ways. Firstly, the elimination of trigger foods will reduce the production of antibodies, which release histamine and inflammatory molecules. This alleviates the ‘load’ placed on the immune system. Secondly, if the body has identified a food item as allergenic or is unable to effectively digest a food it will provoke symptoms. Either due to the body trying to rid itself of the food item or through the bacteria fermenting the substance in the large intestine. In either situation, removal of the food item from the diet will alleviate these symptoms.
The way we live can be detrimental to our gut health. Various factors can contribute to compromising the integrity of the gut and disrupting optimum digestion and absorption; diet high in sugar, caffeine, alcohol, smoking, high levels of mental and physiological stress and hormones. Antibiotics and medications can affect gut bacteria levels. The daily diet has the ability to either positively or negatively affect gut health. A diet that positively affects gut health is one, which is rich in probiotic foods, contains low levels of added sugar and high in fibre or prebiotic foods.
Probiotic foods contain live bacteria. Good probiotic foods are those, which have been fermented or have used bacteria in the production process such as plain yoghurt, goat’s cheese, soft cheeses, pickles, kefir, tofu, miso, tempeh and sourdough bread.
Probiotic foods are those, which provide sustenance to the gut bacteria, allowing them to feed and flourish. They particularly like fibrous foods such as bananas, onions, leeks, pulses, root vegetables, whole grains and oats.
What are the implications of a vegan or vegetarian diet with regards to gut bacteria?
This is an area that continues to be researched and debated. One certainty is that the content of an individual’s diet is reflected in their gut microbiota and the vegan and vegetarian diets lead to changes in strains of bacteria present. However, over what period of time this change takes place needs further investigation. The vegan diet appears to enhance the levels of protective bacteria strains such as F. praunsnitzii and reduces the levels of pathogenic strains such as Enterobacteriaceae. Such changes stemming from the vegan diet are thought to have protective health benefits; the key may be reduced levels of inflammation.