We know that allergies are caused by our immune system over-reacting, but new research shows our gut has an important role to play too.
Runny nose, itchy skin, bloating? You might not immediately think your gut is linked to any allergies you have, but some research is now suggesting that a ‘leaky gut’ may have a key role in causing allergies.
The immune-gut link
More than 70% of your immune system is found in your gut, in the form of a type of lymph tissue called gut-associated lymphoid tissue (GALT).
Your gut’s role in immunity is complex. But as a rough guide, you can see your gut as a sort of gatekeeper; it lets beneficial substances in and out but stops foreign bodies – such as bacteria, funguses and viruses – getting out through its lining.
So your gut is meant to be permeable up to a point, but sometimes this complex process goes wrong. Proteins line the gut in a single layer and are meshed together tightly to form barriers, especially in certain parts of the bowel. If those links become too loose, unhelpful substances can leak into the bloodstream.
This is known as a ‘leaky gut’, but it’s a bit of a controversial topic.
What causes a leaky gut?
Doctors agree that certain conditions can cause an increase in gut permeability. The classic one is coeliac disease, an autoimmune condition that causes an adverse reaction to gluten, a protein found in grains including wheat.
If you have coeliac disease and eat foods containing gluten, your gut lining becomes very inflamed and more permeable, which can lead to a range of symptoms including fatigue, rashes, diarrhoea, bloating, and pain.
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Other conditions, including inflammatory bowel disease (IBD), Crohn’s disease and ulcerative colitis, can also damage the gut lining and potentially cause leakiness.
Alcohol and certain medications including non-steroidal anti-inflammatory painkillers, such as ibuprofen, can also cause irritation and damage the links in the gut lining.
Other causes of leaky gut
Some practitioners believe leaky gut is much more widespread. There’s a theory that a condition called ‘leaky gut syndrome’ is caused by a range of common factors, such as use of antibiotics, poor diet, stress, an imbalance in gut bacteria and/or a yeast overgrowth in the bowel.
The theory goes that these factors cause the bowel to become very permeable and leak undigested food particles and germs into the bloodstream. This is believed to lead to symptoms including asthma, eczema, migraine, food allergies and fatigue.
Your GP probably wouldn’t agree with this idea. Most conventional doctors, including gut specialists, don’t believe the gut can become leaky in most people due to our diet or other everyday factors. And they think even when the gut is leaky because of conditions like coeliac disease, it only leads to gut inflammation and doesn’t cause problems elsewhere in the body.
New studies on leaky gut
However, some emerging research suggests that leaky gut may be linked with a wider range of problems than originally thought. In 2016, a study from Cornell University in the US found people with chronic fatigue syndrome (CFS), had signs of inflammation in their bloodstream, probably because bacteria had leaked through the gut wall. Their microbiome – the community of bacteria living in the gut – were also different to those of healthy people.
Other research has suggested children with eczema may have leaky guts. And when scientists looked at the relationship between migraine and gut disorders, they found people with conditions like IBS and IBD were more likely to experience migraines – this link could be due to the gut leaking inflammatory substances causing the headaches.
Some practitioners think the problems caused by leaky gut don’t stop there. A leaky gut is thought to be one of the underlying causes of an overload of histamine intolerance. Histamine – a chemical released in an allergic reaction, which is also found in certain foods – can cause allergy-type symptoms including brain fog, headaches, eczema and digestive problems when it’s released in large amounts.
A histamine overload can happen partly due to a lack of the enzyme DAO. A small 2015 study found 70% of cases of histamine intolerance could be linked to DAO deficiency. DAO mixes with food in the digestive tract where it breaks down histamines. If you don’t have enough DAO, you could be left with high levels of histamine in your body, which is believed to contribute to gut leakiness.
Eat to heal your gut
While the jury’s out on the extent to which leaky gut causes allergy symptoms – and which comes first, the allergy or the leaky gut – a healthy diet can help.
The fibre in fruit and vegetables is very important as it feeds good gut bacteria. These good bacteria help you release important vitamins and minerals from food which strengthen your barriers to the environment, including the lining of the lungs and gut.
Taking ‘friendly’ bacteria supplements may be useful, too, as they can help boost the gut’s immune cells.
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Advice is for information only and should not replace medical care. Please consult a doctor or healthcare professional before trying any remedies.
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