How Can Gut Health Contribute to Alzheimer’s Disease?

A tree with AlzheimersJune is Alzheimer’s Disease Awareness Month, and we at Atrantil wanted to shed some light on the research between Alzheimer’s disease and gut health. 

The balance of our gut microbes has been linked to so many different conditions, and Alzheimer’s disease and dementia are some of them. While the microbiome is affected by multiple factors, diet is often one of them that is most easily controlled. 

In this article, we will help you understand the specifics of the link between Alzheimer’s disease and the balance within your gut microbiome. 

What is Alzheimer’s Disease?

Alzheimer’s disease is one of the leading causes of dementia. Contrary to what most believe, Alzheimer’s disease and dementia are not the same things. 

Dementia is a condition in which there is a decline in cognitive function, motor skills, and the ability to do daily self-care practices. Alzheimer’s disease actually accounts for about 60-70% of the cases of dementia. 

Alzheimer’s disease (AD) is a neurodegenerative condition where amyloid-beta plaques and neurofibrillary tangles are found in the brain. The plaques and tangles inhibit normal neuron communication and contribute to neuronal loss. Alzheimer’s disease will start with slight confusion and escalate to loss of complete mental functionality. 

What causes Alzheimer’s disease?

Unfortunately, there is no one exact cause of Alzheimer’s disease. There are plenty of factors that come into play when figuring out the etiology of each unique case of AD. However, there are a few factors that have become clear by researchers to have a potential hand in the development of the disease. This can include (but isn’t limited to):

  • Genetics
  • Environmental conditions
  • Immune system dysfunction
  • Mutations in amyloid precursor proteins (APP)
  • Medications
  • Inflammation
  • Infections
  • Gut microbe disturbances
  • Poor diet

While some of these factors are unavoidable, there are a few you have some control over. One that can control most of these factors is your diet. This is because diet affects your gut microbes and they affect your immune and central nervous system via the gut-brain axis.

 

What is the gut-brain axis?

The gut-brain axis is a series of pathways that connect your gut to your brain. Some of these pathways are physical while others utilize messenger cells to connect and communicate with each other. 

Some of the main communication pathways of the gut-brain axis include:

  • The vagus nerve (a nerve that runs from the base of your brain down to your gut)
  • Short-chain fatty acids (SCFA — metabolic byproducts of fiber being fermented in the gut) examples include butyrate, acetate, and propionate
  • Neurotransmitters (90%+ of our serotonin is derived from the gut)
  • Gut microbes
  • Hypothalamic pituitary adrenal (HPA) axis 

All of these factors work together to form an easy way for your gut to talk to your brain. The enteric nervous system(ENS) is actually referred to as the second brain because of how much interaction and control it has over your brain. The ENS is the only other body part that can function independently of the stimulation from your CNS.

Most of the pathways mentioned above reside in your gut. We’ve always thought of our brain controlling everything that happens in our bodies, so it isn’t a surprise to say that it can control our gut too. However, our gut controlling our brains is the part that most people don’t understand. 

When we consume foods, our gut must break them down into smaller particles that the body is able to use. In its raw form, we can’t use any foods. It’s only once the digestive process begins (with increased saliva production and chewing our food) that we are able to actually extract nutrients from the foods we eat.

The byproducts of our digestive processes are what we need from our foods. And these byproducts are what help our gut to guide our brain functions. 

How does the gut affect Alzheimer’s disease development?

There are several ways your gut can affect your potential for developing AD. Most of them derive from the foods we put in our guts and how well we take care of our gut. Certain foods will cause problems within our gut and lead to disease. 

The problems most to blame include:

  • Gut inflammation/gut barrier dysfunction
  • Lipopolysaccharides
  • Bacterial amyloids

Let’s look at each of these a little deeper.

Spoon with food flying off of itGut Inflammation/Gut Barrier Dysfunction

Gut inflammation is a major concern when it comes to health. When the gut barrier is inflamed, it allows for the translocation of bacteria from the gut throughout the body which creates systemic inflammation

Looking at stool samples of those with intestinal inflammation, researchers often find a protein called calprotectin. Calprotectin is a calcium-binding protein that has antimicrobial properties and contributes to the health of our neutrophils (a type of immune cell). The structure of calprotectin is a similar amino acid structure to that of amyloid polypeptides like amyloid-beta and alpha-synuclein. 

Calprotectin has been found in increased quantities in the cerebrospinal fluid of Alzheimer’s patients — likely due to the translocation from the gut barrier dysfunction.

Lipopolysaccharides

Lipopolysaccharides (LPS) are endotoxins that have been linked to many diseases like chronic gut inflammation, diabetes, and neurodegenerative disorders.  LPS feeds off of sugars and fats. The increase of these foods causes a rise in LPS circulation and therefore inflammation in the gut and throughout the body. This constant state of inflammation creates a fever-like response within the body that doesn’t go away like when you’re sick. 

The inflammation then causes damage to the surrounding tissues which eventually leads to disease, like in the case of AD.

Bacterial Amyloids

Amyloids are often associated with strictly Alzheimer’s disease and the CNS. However, there are bacterial amyloids that reside in the GI tract. The most commonly studied bacterial amyloid is called curli and it is produced by the bacteria Escherichia coli. While in the gut it is fine and our bodies are equipped to fight it off, the exposure to curli can cause the immune system to create all amyloids (even those intentionally expressed by our bodies for good things) as invaders. This means that our immune systems will be hypersensitive to them and attack the amyloids endogenously created causing plaques to be formed and inflammation within the CNS. 

Any of these can be the beginning of the development of Alzheimer’s disease. So doing your best to reduce their impact will set you on a better track.

How can you manipulate your gut-brain axis to best prevent Alzheimer’s disease?

The gut has many requirements to maintain homeostasis and health. Luckily all of those requirements add up to a healthy body. While we can’t promise that following these will absolutely ensure you don’t end up with diseases (since there are so many external factors to worry about) we can say with certainty it will help!

  1. Eat a healthy, well-balanced diet (Check out polyphenol filled diets like the MIND diet — a diet created exclusively for those at high risk for AD)
  2. Exercise regularly
  3. Make getting good sleep a non-negotiable
  4. Meditation

You can find more information about how these will help you to fight off Alzheimer’s disease in our article here

How Can Gut Health Contribute to Alzheimer\'s Disease?How Can Gut Health Contribute to Alzheimer\'s Disease?