Leaky Gut = Leaky Blood Brain Barrier

What is the blood brain barrier?

The blood brain barrier (BBB) is effectively our brain’s own ‘policing system’, a physical barrier that separates our blood circulation from the central nervous system, which includes our brain. The deterioration of this highly intelligent barrier has been linked to many neurological conditions, one of which is Alzheimer’s, the most common form of Dementia (1). Up until recent years the complexity of the BBB was not fully understood, researchers believed that any molecule small enough could penetrate it. However, new technology that allows scientists to look into the brain to a depth of a millimetre, whilst the brain is still functioning, has revealed just how complex this layer of cell junctions actually is (2)

What does the blood brain barrier do?

The homeostatic function of the BBB is essentially to protect the brain from exposure to molecules such as pathogens, viruses and toxins, as well as many other compounds, which can be toxic to the brain. This tightly regulated system is managed by endothelial cells which are closely-fitted together and a myriad of molecular passageways embedded in the membrane of the cells (3) These intelligent structures work by actively pushing molecules across that the brain requires such as nutrients and blocking others that are harmful. It can be likened to having our very own border control, filtering out what we need and don’t need.

Neurological conditions such Alzheimer’s and Parkinson’s, as well as mental health conditions such as depression and psychosis, have been linked to a leaky blood brain barrier, where the tight junctions become lose, therefore allowing through molecules which would otherwise not have been able to (4). Until recent years, dysfunction of the central nervous system and neurodegenerative disease in particular, has excluded the impact of factors outside of the central nervous system. Peripheral factors such as toxins and the adaptive immune system have been shown to play a significant role in the pathogenesis and the development of neurodegenerative disease (5)

The link between gut health and a compromised BBB

A recently conducted study has revealed how a key influencing factor in the permeability of the BBB may well be our gut bacteria. Tests carried out on germ-free mice with no normal gut flora displayed increased blood brain barrier permeability compared to those with normal gut flora. Furthermore, the results demonstrated a reduced expression of the cell junction proteins, which regulate the function of the barrier in endothelial cells (6). This led to a reduced development of nerve cells in the hippocampus, the area of our brain which is known for where we process memory and emotions (7). Studies like these further strengthen the theory that the gut and the brain work in tandem and are in constant communication with each other.

Gut bacteria have the crucial role of producing metabolites, such as short chain fatty acids, that provide fuel to the cells in the lining of our gut. This is essential to prevent permeability in the tight cell junctions embedded in the wall of our intestines. Just like the blood brain barrier, the intestinal wall prevents toxins and bacteria from leaking into our bloodstream and triggering a cascade of inflammation. And it’s exactly this source of inflammation that compromises the blood brain barrier.

Factors that compromise gut bacteria

Medications such as antibiotics, antacids and common painkillers have been known to significantly impact the diversity and number of bacteria in a negative way. A study undertaken in Norway tested 1135 participants to measure how environmental factors such as diet and medication influence bacteria. Results revealed that our bacteria can be affected by up to a year after taking antibiotics (9). 

A diet high in processed foods, low in fibre and high in sugar, has also been shown to lead to low diversity in our gut bacteria, as well as the growth of unfavourable gut bacteria strains, which are disease-inducing and can lead to problems like leaky gut.

Factors that improve gut bacteria balance and blood brain barrier function

• Prebiotics

Our gut bacteria thrive on prebiotics, which are undigestible fibres found in starchy vegetables such as sweet potatoes, butternut squash (and other types of squash), beetroot, parsnips, plantain, celeriac and jerusalem artichoke. When gut bacteria begin to ferment the resistant starches in these foods, they produce those amazing short chain fatty acids previously mentioned, which nourish the intestinal wall and keep the tight cell junctions intact.

• Probiotics

Fermented foods such as sauerkraut, kimchi, miso, tempeh, kefir and natural yoghurt all contain friendly bacteria that help to keep the ecology of your gut in balance.

• Avoiding gluten

Gluten has been shown to elevate “zonulin” , which is a protein in your body that increases the permeability of the intestinal barrier and consequently disrupts the blood-brain barrier.

• Eating sulforaphane rich food

Sulforaphane is a phytochemical that is found abundantly in foods such as broccoli, Brussels sprouts or cabbages. These amazing compound increases a major antioxidant in the body called glutathione, which helps to prevent the breakdown of the blood brain barrier.

• Increasing antioxidant rich food

Antioxidants are molecules that are able to prevent free radicals - unstable molecules - from creating damage in the body and in the brain. Because the brain is so sensitive to oxidative stress, due to its high demand in oxygen, it is essential to be eating antioxidant rich food on a daily basis to quench oxidative stress, which can lead to permeability in the blood brain barrier. Foods such as berries, cacao (this doesn’t mean sugary chocolate, this is pure cacao) and green tea, are some of the richest sources of antioxidants, as well as green leafy veg, beets and tomatoes.

• Omega 3

Omega 3 is high anti-inflammatory and it is for this reason that it is so great in preventing a compromised blood brain barrier. Specifically, its the EPA component of omega 3 fatty acids that has an anti-inflammatory function. Eating small oily fish, such as sardines, herring, mackerel, anchovies and pilchards are the best way to get good quality omega 3 in the diet. However, in cases of poor mental health, it is absolutely necessary to supplement high levels of omega 3 to repair the blood brain barrier and quench neuroinflammation.

There are many more factors that can prevent the blood brain barrier from becoming compromised, however, I wanted to keep it to the most important factors, which I have seen have made the most difference in clinical practice. If you’d like to find out more about how I can help you with your brain health, book in a discovery call with me below.