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It's common knowledge that what you eat affects your health, but recently there's been increased focus on how the gut, or digestive tract, might be a particularly important part of this relationship. The general consensus is that a healthy gut supports a healthy body, and for some people an unhappy gut might even lead to the development of food intolerances.
Food intolerances have a number of symptoms and can cause further dysfunction and disease. Unfortunately, they can be difficult to diagnose as, unlike allergies, symptoms are not clear-cut and the testing for them is not a simple task. Some people may even experience intolerances for years before ever being diagnosed.
When you hear people talk about the gut you'll likely hear the terms 'biome' or 'microbiome'. Put simply, these terms refer to the collection of both good and bad bacteria that exist in your gut.1 When the balance between these bacteria is just right your gut is likely to be healthy, which in turn can help promote better overall health.
The digestive tract, is expansive (spanning from mouth to colon), and microorganisms live throughout: the majority are located in the large intestine, whilst only a few species are found in the small intestine and stomach.2 One common misconception is that because the biome is predominantly in the gut, it must only affect digestive health. But it plays a vital role in other areas like immunity, metabolic health and protecting against pathogens and disease.3
A food intolerance is a negative reaction to a food, drink, or compound within a food. It's generally a slow reaction, with symptoms taking minutes or even hours to develop. Some triggers, such as lactose, are quite common, whilst others are more obscure, such as salicylates - which are commonly found in herbs and spices like curry powder and turmeric.4, 5
A food intolerance is usually caused by an inability to digest and absorb a food properly. There are a number of causes for this, but typically it is caused by a deficiency of an enzyme, malabsorption of a compound, or an improper response from the immune system to a food.
Some symptoms of a food intolerance can include:
Unlike allergies, which generally occur from an early age, a food intolerance can develop at any time. This is likely, in part, because the health of the digestive tract can play an important role in its development.
One example of this is malabsorption of nutrients from the gut into the body. Someone who has a fructose intolerance, for example, cannot absorb every bit of fructose and some therefore remains in the gut. This leftover fructose can then ferment in the gut, and produce symptoms such as gas, in addition to feeding the 'bad' bacteria in the gut, leading to an imbalance in the biome.7, 8
Food intolerances have also been linked to leaky gut. When the gut wall is more porous than it should be it allows particles to enter before they are fully digested. These particles can cause inflammation throughout the body, alerting the immune system, which in turn can't recognise the particles and flags them as invaders. From then on, the body may react to those flagged particles to protect itself. This is a vicious cycle as autoimmune reactions can worsen leaky gut syndrome.9, 10, 11
A healthy biome can protect the gut lining by shielding it from pathogens and minimising inflammation in the gut.12 Therefore, optimising the gut flora is essential when it comes to repairing leaky gut and intolerances.
If intolerances are caused by a digestive issue, healing the gut could be an important step in reducing or even eliminating an intolerance. There are a few key steps when it comes to rebalancing the biome, though, with the first being to remove foods that are irritating or inflammatory for the gut. This includes the food you are experiencing an intolerance to, as well as generally unhealthy foods, such as processed foods, alcohol, and high-sugar foods. By cleaning up your diet and ridding it of intolerant foods, under the supervision of a nutritionist, you can reduce inflammation and irritation in the gut so that the healthy microorganisms can re-establish and strengthen in numbers.
The next step is to rebuild the biome by adding in good bacteria. This can be done by consuming more fermented foods such as kimchi, kombucha, sauerkraut and live yoghurt, in addition to taking a daily prebiotic supplement that contains a variety of different bacteria strains. It's also essential to fuel these good bacteria. Probiotics need prebiotics as a food source in order to create a home in your gut; these can be found in foods such as apples, onions, beans, legumes, and oats. Similarly to probiotics, it might also be worth taking a daily prebiotic supplement to make sure you get sufficient amounts.13, 14
Most importantly, you should make sure your overall diet and lifestyle are healthy. Be sure to obtain a wide range of antioxidant-rich and anti-inflammatory foods, reduce your alcohol intake and pursue regular exercise.15
After following these steps for at least four weeks you can try re-introducing the food you were intolerant to. Some people may need to follow a restricted diet (under the supervision of a nutritionist to avoid deficiencies) for longer, depending on the state of their biome when they started. This should be done under the supervision of a nutritionist, to prevent deficiencies. If you have multiple intolerances or a chronic condition you should consult your local GP for support throughout this process.
It's important to remember that food intolerances aren't the same as food allergies. An allergy is an immediate, and often severe, immune response to a food that can be life-threatening.16, 17 It's important to know the difference and above all to consult your GP if you think you might have an allergy or be intolerant. In terms of what you can do now, a good starting point is to make sure your diet is healthy and that you consume a good amount of probiotic and prebiotic fibres from both foods and daily supplements. If you're interested in learning more about the gut, Select Digestion from the Your health menu above.
Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.
1Hannigan, G. D., Meisel, J. S., Tyldsley, A. S., et al. (2015). The Human Skin Double-Stranded DNA Virome: Topographical and Temporal Diversity, Genetic Enrichment, and Dynamic Associations with the Host Microbiome, mBio, 06(05)
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16Boyce, J. A., Assa’ad, A., Burks, A. W., et al. (2011). Guidelines for the diagnosis and management of food allergy in the United States: summary of the NIAID-sponsored expert panel report, Journal of the American Academy of Dermatology, 64(01)
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