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Why Gut Health Matters For Depression And Anxiety

Publication date: 25 October 2013

Most people would quite readily accept that the brain can affect gut function. We know from experience that stress can create strange sensations, such as butterflies, or worse, symptoms such as diarrhoea , pain or IBS. But you may not realise that gut-brain talk is a two-way street, to the extent that it is. Science is revealing the details of the connections, giving substance to the not-quite-mainstream medical opinion that healing the gut is vital to emotional and mental health.

Here's how it works.

1. Physical or emotional stress affects the microbiota, or gut flora (population of bugs living in the gut).

One way this can happen is via the stress hormone cortisol. High levels suppress the gut's first line immune defence, secretory IgA, opening the door to harmful bacteria such as helicobacter pylori, or the yeast candida albicans, which may proliferate at the expense of healthy bacteria.

2. Changes in the microbiota trigger increased gut permeability, meaning that the gut lining becomes somewhat leaky.

3. Toxic molecules can now pass through the gut lining. These trigger the body's immune system to respond.

Lipopolysaccharides are an example of such a toxic molecule. They come from bacteria, and science as shown they trigger a particularly strong immune response.

4. The initial immune response triggers a cascade of immune signalling molecules called cytokines - these trigger a general inflammatory response, affecting many tissues around the body.

5. The blood-brain barrier (BBB) is one tissue that's affected. This is a special protective membrane that lines the blood vessels in the brain - the brain is particularly sensitive to toxins and infectious agents so the body maintains the BBB as a means of tightly controlling physical access to the brain. But the BBB is not immutable and, like the gut lining, can become leaky.

6. On the other side of the BBB, the brain in a sense has its own immune system in the form of glial cells, which can be stirred to create brain-side inflammation too.

7. Brain inflammation can cause:

  • altered neurotransmitter levels
  • changes in neural excitability and communication
  • and ultimately psychological and behavioural changes, including some that are characterised as depression and anxiety, also brain fog and chronic fatigue.

8. These changes affect stress tolerance and sleep, etc. and thus the cycle begins again.

I've outlined just one possible pathway, of many. The gut-brain connection is not just a two-way street but a multi-channel network. I haven't even mentioned how poor diet can affect the pathways.

All of these steps are well documented by science. With a little creative thinking (and don't read that as unscientific) you can see how it opens the door to a range of non-drug health interventions that could help depression and anxiety. But if your view of science doesn't go beyond the (in my view over-hyped) randomised controlled drug trial, you wouldn't see it.

Fortunately more and more health practitioners are becoming aware of the new science. Functional Medicine (FM) is a new paradigm of health based on systemic thinking and integrative, personalised therapy. Functional Medicine sees illness in terms of imbalance in underlying body systems, and tries to support the body's own mechanisms to bring back balance and health.

As a qualified Nutritional Therapist I take a great interest in FM. I hear from colleagues that FM is really taking off in the states - how far behind is the UK?

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