Are food allergies genetic?

The reasons behind food allergies are diverse, and currently there exists a situation where the only available prevention for food allergies is to avoid the foods that you are allergic to altogether. We investigate the causes of allergies, by looking at genetics, the environment and their relationship.

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The difference between allergies, sensitivities and intolerances 

There are definite and distinctive differences between allergies and a sensitivity or an intolerance. A food allergy is where your body or rather your immune system reacts to the food. While a sensitivity or an intolerance is a reaction to a certain type of food, for example milk or wheat, is a result of a reaction from your digestive tract.

In most cases, an allergic reaction to one type of food (such as prawns) may mean that a person might be susceptible to reactions from other similar types of food (such as crayfish or crabs). This is because allergies and the properties in the food causing an allergy are linked.

In this article we’ll delve into the research surrounding food allergies and identify the causal links between genetics, the environment and other factors that can account for why some people have allergies, and others don’t.

Common food allergies

Up to two million, or 8% of children in the United States are affected by food allergies. Making up 90% of all food allergies are: eggs, milk, peanuts, nuts, fish, shellfish, wheat, and soy.

According to Kids Health, here is a brief breakdown of each of these allergies:

  • Cow's milk: Between 2% and 3% of children younger than three years old are allergic to the proteins found in cow's milk and cow's milk-based formulas. Most formulas are cow's milk-based. Milk proteins can be a hidden ingredient in prepared foods. Many kids outgrow milk allergies.
  • Eggs: Egg allergy can be a challenge for parents. Eggs are used in many of the foods kids eat — and in many cases they're classified as "hidden" ingredients. Kids tend to outgrow egg allergies as they get older.
  • Fish and shellfish: These allergies are some of the more common adult food allergies and ones that people usually don't outgrow. Fish and shellfish are from different families of food, so having an allergy to one does not necessarily mean someone will be allergic to the other.
  • Peanuts and tree nuts: Peanut allergies are on the rise, and as are allergies to tree nuts, such as almonds, walnuts, pecans, hazelnuts, and cashews. Most people do not outgrow peanut or tree nut allergies.
  • Soy: Soy allergy is more common among babies than older kids. Many infants who are allergic to cow's milk are also allergic to the protein in soy formulas. Soy proteins are often a hidden ingredient in prepared foods.
  • Wheat: Wheat proteins are found in many foods, and some are more obvious than others. Although wheat allergy is often confused with celiac disease, there is a difference. Coeliac disease is an autoimmune disease where you see a reaction from the gluten that is found in food containing wheat.  Celiac disease is a sensitivity to gluten (found in wheat, rye, and barley). But a wheat allergy can do more than make a person feel ill — like other food allergies, it also can cause a life-threatening reaction.

What causes food allergies?

Food allergies usually appear in the first years of life and manifest themselves in the form of itchy rashes and facial swellings, which occur shortly after food ingestion. Food allergies can, however, also cause severe allergic reactions involving breathing difficulties, vomiting, or diarrhoea, and are the most frequent triggers of anaphylaxis in children. Anaphylaxis is the most extreme form of an immediate allergic reaction and can be life threatening.

While many people with allergies develop them during childhood, it is still possible for people to develop allergies at any stage of their lives. This is also true for people who may have had an allergy when they were younger and had it go away, only for it to return later in life.

Are allergies genetic or environmental?

Can allergies run in the family? It has been found that a person’s genetics could play a key role in understanding why they have certain food allergies, as these allergies could be hereditary.

What is known is that although there are also environmental factors at play, which will be discussed further down, the likelihood of a person having an allergy increases if one or both parents have the same allergy.  

The human genome contains a vast amount of information and data to do with everything about a person, the key lies in adequate research being done so genes can be understood in more detail.

Research on genetics and food allergy

In their study, the Johns Hopkins Bloomberg School of Public Health-led research team, principle investigator, Dr Xiaobin Wang, MD, ScD, MPH and her colleagues analysed DNA samples from 2,759 participants (1,315 children and 1,444 of their biological parents) enrolled in the Chicago Food Allergy Study. Most of the children had some kind of food allergy. They scanned approximately 1 million genetic markers across the human genome, searching for clues to which genes might contribute to increased risk of developing food allergies, including peanut.

They found that a genomic region harbouring genes such as human leukocyte antigen(HLA)-DQ and HLA-DR and located on chromosome six is linked to peanut allergy. This study suggests that the HLA-DR and -DQ gene region probably poses significant genetic risk for peanut allergy as it accounted for about 20 percent of peanut allergy in the study population. This is also the same location that predisposes people to an increased risk of coeliac disease.

In another study, the so-called SERPINB gene cluster on chromosome 18 was also identified as a specific genetic risk locus for food allergies. It involves ten members of the serine protease inhibitor (serpin) superfamily. The genes in this cluster are expressed primarily in the skin and in the mucous membrane of the oesophagus. The researchers thus suspect that they play a major role in ensuring the integrity of the epithelial barrier function. Another important finding of the study is that four of the five identified risk loci are associated with all food allergies. The HLA region, which is specific to peanut allergy cases as stated above, appears to be the only exception.

Studies such as this reveal the value in continuing research in the field of genetics for the benefit of society as a whole. Insight into genetics and the reasons behind why all people are unique and different from each other can offer key ways to understanding food allergies better.

Environmental factors and the development of allergies

As mentioned above, our environment plays a significant role in both our daily lives and in us potentially developing an allergy. A study discovered that the role of gene-environment interaction, gene-gene interaction, and epigenetics in food allergies remains largely unexplored and more research is needed to understand these relationships better.

Given the complex nature of allergies, future studies need to integrate environment, genomics and epigenomics in order to better understand the multi-facet etiology and biological mechanisms of food allergies.

As this field of science grows, being relatively new, the understanding of the relationship between the environment and genetics and what it means to the people it impacts will assist us in furthering our knowledge of how to prevent, treat, and possibly one day cure food allergies that have a debilitating effect on the lives of the people who have them.

Other factors that have been linked to allergies include the surrounding environment and lifestyle habits including:

  • Exposure to smoke
  • Exposure to certain products such as cleaning liquids
  • Household pets
  • Exposure to other children with allergies
  • Viral infections
  • Vaccinations
  • Medications
  • Air pollution
  • Diet

While these factors don’t necessarily cause food allergies per se, there is a possible association between lifestyle and the environment.

Gender-related allergies

Finally, a study has also found that allergies could be gender-related depending on which parent has an allergy. In short, maternal allergy increased the risk in girls and paternal allergy increased the risk in boys. This has implications for childhood allergy prediction and prevention as this information could be used to determine, based on the sex of a child, if they are more likely to have an allergy. However, there is always a risk associated with one parent having an allergy and therefore precautions should be taken with certain foods after a child is born.

What does DNAFit test for?

The DNAFit test, first and foremost, is not to be used as a diagnostic tool under any circumstances. It can provide insights into your response to certain foods but, in terms of allergies, you should always consult with a medical practitioner. 

DNAFit does, however, test for the following food intolerances (not allergies):

  • Lactose intolerance
  • Coeliac disease predisposition

Lactose intolerance

Roughly 65% of the world’s population lose the ability to digest lactose, the sugar found in milk, after weaning. From an evolutionary perspective, this makes sense – humans typically need to digest milk when they are babies because their main source of nutrition is breast milk; however, once the child has stopped breast feeding, historically there was no need for them to continue to digest lactose, because milk wasn’t readily available.

However, as humans migrated out of Africa into Asia, and eventually into Europe, a small polymorphism occurred which enabled some of them to continue to digest lactose into adulthood. This was useful because it now meant that instead of killing their animals for meat, they could consume their milk, thus creating a renewable source of nutrition. This, in turn, allowed humans to migrate even longer distances, spreading into Northern Europe. Today, between 85-95% of Britons are lactose tolerant, compared with around 60-75% of Southern Europeans. The number of lactose tolerant individuals gets smaller as we move into Asia and Africa; in some places 100% of the population are lactose intolerant.

Instead of being absorbed through the small intestine, the undigested lactose travels to the colon, where bacteria begin to break it down via fermentation. This process creates a lot of gas, which leads to the symptoms associated with lactose intolerance – bloating, stomach cramps, excessive gas, or diarrhoea. The main cause of lactose intolerance is called primary lactose intolerance; this is where the body doesn’t produce lactase, the enzyme that breaks down lactose. This is genetic, and determined by the LCT SNP.

The LCT SNP has three possible allele variations CC, CT or TT. The T allele  is what gives people the ability to continue to produce lactase, the enzyme which digests lactose, into adulthood.

In summary then, if you have a T allele, you have the ability to produce lactase, which means you should be able to tolerate milk products. Those without a T allele you will likely have lost the ability to produce lactase, and as such will be unlikely to tolerate milk products. However, it’s worth pointing out that having at least one T allele doesn’t guarantee that you can tolerate milk products; this is because some people might have something called secondary lactose intolerance, which is not genetic, and is instead often caused by a bacterial infection, virus, or stomach injury/disease (such as irritable bowel syndrome ). It’s also possible to be lactose tolerant, but have a cow’s milk protein allergy – although this affects less than 1% of people. The flipside of this is that even people with lactose intolerance can often consume small amounts of lactose without any symptoms.

Nevertheless, knowing and understanding your LCT genotype can be important when it comes to seeing which foods you can tolerate, and explaining why you might experience certain symptoms with milk products.

Coeliac predisposition

Coeliac disease is an autoimmune condition that affects the small intestine. If you have coeliac disease, and you consume foods that contain gluten and/or wheat , you will likely suffer from symptoms include diarrhoea, abdominal pain, unintentional weight loss and malabsorption. This is because the presence of gluten causes a reaction in the microvilli, which are finger-like structures found in the small intestine. Their purpose is to increase the surface area of the intestines, allowing for greater absorption of vitamins and minerals. However, in people with coeliac disease who consume gluten, these microvilli become blunted and start to disappear – a process known as villous atrophy. This makes it much harder for the body to absorb nutrients, which in turn can causes uncontrollable weight loss and vitamin and mineral deficiencies.

The DNAFit test, then, can’t tell you whether you do or don’t have coeliac disease. The only way to know for sure if you have coeliac disease is through a small bowel biopsy, which would be done by a doctor. Instead, DNAFit can tell you your likelihood of developing coeliac disease.

Everyone’s risk of developing coeliac disease is 1/100 – and this is true until we test your genes. If we see that you haven’t got the HLA DQ2/DQ8 genes, then your risk of developing coeliac disease is very low; about 1 in 2000. If you have got the HLA DQ2/DQ8 genes, then your risk is elevated to 1 in 35. Still pretty good odds in your favour that you won’t have coeliac disease, but worth being aware.

So, how can you use this information? It’s worth reiterating that the DNAFit test can’t tell you whether you have or haven’t got coeliac disease, or whether you can or can’t get it. It can just tell you the likelihood of developing it. Even if you have a low genetic risk of 1 in 2000, that still means that you can develop coeliac disease.

Conversely, having a higher risk of developing coeliac disease does not mean that you will. It’s worth pointing out that the only known management for coeliac disease is a gluten free diet. However, if you have the HLA DQ2 or HLA DQ8 genes, there is no reason for you to start eating this way. Instead, you should monitor how you respond to gluten containing foods. If you start to develop diarrhoea or abdominal cramps, or feel run down or anaemic, and have a high risk of coeliac disease as per the DNAFit test, it might be worth speaking with your doctor in order to have a proper medical examination.

In summary

To conclude, allergies are mostly contracted from birth and depending on the allergy, children with allergies are likely to carry it throughout their entire lives. However, it is still possible to develop allergies later in life, and in contrast, develop a resistance to whatever is making you allergic, it all depends on your body.

What we know about allergies is that they are caused by genetics and your environment. While the likelihood of a person having an allergy will be higher if one or both parents have an allergy, there are still environmental impacts to take into account that can cause an allergic reaction.

Research surrounding allergies is still developing, and hopefully in time we will understand how to manage or prevent them outside of simply through avoidance of the cause of the allergy. With the growth of genetic and epigenetic research, we are perfectly set in this moment in time to further our knowledge of allergies.

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