The easy answer is to say that many of them are hereditary, but the human body tends to reject easy answers. For example, because often what we think is an intolerance is actually an allergy. Let’s take it one step at a time.
Have you ever found a correlation between eating a particular food and your body suffering afterwards? You are possibly facing an allergic reaction (if your immune system is involved) or an intolerance reaction (if your immune system has nothing to do with your suffering).
Intolerance is more common than allergy, and there are several types of intolerances, because variety is the spice of life, classified into three groups. Let’s take a look at some of them so that you can understand the information that tellmeGen’s genotyping tests can give you.
Food intolerances, the immune system is quiet
Food intolerance with an enzymatic or metabolic cause, the most common, is due to the body’s inability to metabolise specific substances in food, which cause the alterations. This is because the genome encodes deficient enzymes for these metabolic pathways. Within this group, lactose intolerance is the major representative.
Lactose intolerance is a curious situation. Lactose metabolism is carried out by lactase, which is produced by the cells of the intestinal epithelium and breaks down lactose into glucose and galactose. However, the gene that carries the lactase information, LCT, in these individuals functions normally and without unusual mutations. But over time it becomes less expressed, less of the enzyme is synthesised and undegraded lactose accumulates, causing abdominal pain, gas and diarrhoea. This is because the real cause of the problem is the MCM6 gene, a regulatory gene that modulates the expression of LCT and decides how much protein is produced. Its status can be seen with a genetic test for lactose intolerance.
This is not to be confused with congenital lactose intolerance, where lactase is either useless or not produced at all and the illness is present from birth. In our case, people gradually lose the capacity, being less severe than congenital lactose intolerance, and many are still able to consume dairy products such as cheese and yoghurt, although not milk.
Fructose intolerance would also be found in this group. Referred to as fructosaemia or ‘hereditary fructose intolerance’, the term fructose intolerance is often used for the condition due to problems in its absorption in the gut, with no enzymatic cause. When absorption fails, the ‘bad guys’ are the fructose transporters in the intestinal epithelium. In our case the ‘bad guy’ is the enzyme aldolase B, which is found in the liver, and is involved in the breakdown of fructose into glyceraldehyde and dihydroxyacetone phosphate, but we have it malfunctioning. Simply put, fructose builds up and messes up your liver and kidneys.
In addition, not being able to work that sugar, it throws the body’s energy pathways out of balance and lowers blood glucose. Fructose is not only found in fruit, but is also one of the components of sucrose, and is used in industry as a sweetener, being the sweetest sugar of all.
On the downside, it is an autosomal recessive disease (you need both genes altered to suffer from the disease) and, by controlling fructose in the diet, it has no other symptoms or alterations. Because the disease is due to the ALDOB gene, the genotyping we perform at tellmeGen allows us to know for sure if you have the functional form or the recessive form that causes the intolerance.
Another type of intolerance is the pharmacological or chemical intolerance. This is not necessarily caused by enzymes, but it is an abnormal reaction to substances present in certain foods.
This group includes histamine intolerance. Histamine is produced naturally by our body and its best-known function is as a messenger of the immune system. For example, it is one of the main causes of immediate hypersensitivity reactions, i.e., allergies.
Although it can be caused by over-consumption of histamine, it is usually because the body is unable to break it down correctly due to errors in the DAO enzyme pathway (yes, it falls into the group of chemical intolerances, but enzymes can still be the culprit). At tellmeGen we look at the AOC1 gene, which encodes the DAO enzyme, to test your ability to metabolise histamine. Individuals with this intolerance present with a clinical picture like an allergic reaction.
There is a final type of intolerance, food intolerances of undetermined cause, which are a bit of a catch-all. These include intolerances due to additives and contaminants, which are on the rise due to ultra-processed foods. Psychological food intolerance would fall into this group.
Food allergies, the immune system on the move
Food allergies follow a different route. As the name suggests, they are reactions in which our body considers a substance in food to be harmful and triggers an exaggerated immune response against it. The damage is due, not to the substance itself, but to the immune system’s own reaction that causes the alterations.
One example is peanut allergy. It is one of the most serious food allergies and can lead to death by anaphylaxis. It is also one of the most common allergens and its incidence is increasing. Several peanut proteins, usually Ara h 1, Ara h 2 and Ara h 3, induce the production of immunoglobulin E within the body.
There are several possible causes for developing this allergy, for example, the SNP rs9275596, in the LOC100507686 gene, is associated with an increased predisposition to have it. Thanks to the information provided by your genome, tellmeGen will be able to tell you if you are predisposed to this allergy.
One final fact is that, although it is not uncommon for a person to have both allergies, peanut allergy is different from nut allergy. Among other things, this is because peanuts are not nuts, but are actually legumes.
If you are curious about your genetics’ ability to direct your diet, your tellmeGen DNA kit will not only give you information on allergies and intolerances, you will also learn about your tolerance to alcohol, how much caffeine affects you or whether you have a sweet tooth.