Gut Bacteria May Reveal Alzheimer’s Even Before Symptoms Appear

Alzheimer's disease
Alzheimer's disease
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Alzheimer’s disease (AD) is one of the health-related complications which, owing to its increased incidence, are getting the focus of many researchers these days. A complication resulting due to the slow accumulation of amyloid-beta within the brain, the symptoms of Alzheimer’s disease start appearing after a decade or so since the problem first started. This late diagnosis makes the condition hard to treat and almost impossible to reverse the patient’s health state to normal.


The decline in cognitive efficiency due to AD

Keeping this in mind, researchers nowadays are devising novel ways to make an early diagnosis of AD. In one of such studies published recently in Science Translational Medicine, it has been unveiled that the gut microbiome depicts an alteration if a person has Alzheimer’s disease. Let us dive deeply into what AD is, what new data this current investigation has provided, and learn more about the connection between gut and AD.

What is Alzheimer’s disease?

Alzheimer’s disease or AD is an atrophic neuronal condition mainly characterized by dementia or memory loss which can be mild or severe depending on the severity of the disease. The disease impacts the process of perception, comprehension, thinking, learning, memorization as well as the articulation of speech. The major cause of this brain impairment is the deposition of two distinct proteins i.e. amyloid-beta and tau protein in the brain. These proteins form clusters near the neurons which are subsequently affected.

healthy and affected neurons by Alzheimer's

(a)                                         (b)

A comparison of (a) healthy neurons with the (b) neurons affected by the clusters of amyloid-beta (visible as brown deposits)

Signs and symptoms of Alzheimer’s disease

The signs and symptoms of Alzheimer’s disease include:

  • Dementia or memory loss
  • Disruption of day-to-day activities
  • Being unaware of the recent events
  • Confusion related to time and place
  • Impairment of problem-solving ability
  • Troubled identification of things, places as well as people
  • Inability to communicate
  • Increased sleep intake
  • Difficulty in swallowing
  • Decreased body weight
  • Overall poor health
  • Seizures

The gut microbiome as an AD biomarker

A study was conducted in the USA aimed at evaluating the link between the composition of gut microbiome which may act as a biomarker for the early diagnosis of Alzheimer’s disease. For this purpose, 164 healthy individuals with cognitive abilities intact along with similar dietary choices were recruited and tested for the nature and composition of their gut microbiome. The testing techniques included MRI and PET imaging along with lumbar puncture. Apart from these, cerebrospinal fluid (CSF), blood, and stool samples were also drawn and analyzed. It was found that out of 164, 49 people had an alteration in the types and number of certain bacteria residing in their intestines indicating that these individuals had an early stage of AD. Thus, the findings of the study have confirmed the presence of a direct correlation between the modification within the cranial mass and the gut bacteria. This indicates that at a stage where Alzheimer’s disease has started changing the brain, although not so significantly as the cognitive impairment has not become detectable yet, the gut bacteria are also altered.

gut bacteria and ADHD

The connection between the brain and gut

Although previously published literature has already given insights into the gut-brain connection and how the fluctuation in one of them changes the other as well, the recent study is a breakthrough in terms of detecting pre-symptomatic Alzheimer’s disease.

Notable bacterial species in the gut microbiome

The bacterial species which are found to be altered during dementia and Alzheimer’s disease include:

  • Collinsella
  • Ruminococcus
  • Bifidobacterium

Can I slow down the AD?

Completely bypassing the occurrence of Alzheimer’s is quite impossible at this stage but to delay it is something achievable. With simple lifestyle modifications, this bigger goal can possible within reach. These changes include the following:

  • Management of blood pressure
  • Maintenance of healthy blood sugar levels
  • Regularly exercising
  • Maintenance of healthy weight
  • Getting enough sleep
  • Avoidance of smoking and alcohol
  • Dietary modifications

How to prevent Alzheimer’s disease with diet?

Although it is early to say that by deliberately altering the gut microbiome, one can avoid the incidence of Alzheimer’s disease. However, according to brain experts, certain foods can reduce the chances of getting brain-related impairments if the consumption of certain foods is ensured. These foods famously called the ‘brain foods’, include:

  • Water
  • Coconut water
  • Turmeric
  • Chocolate
  • Broccoli
  • Eggs
  • Almonds
  • Blueberries
  • Wild salmon
  • Avocados
  • Pumpkin seeds
  • Flax seeds
  • Walnuts
  • Chia seeds
  • Whole grain
  • Tea
  • Coffee
  • Probiotics
  • Vitamin supplements
  • Zinc

Food for brain health

Some of the foods highly beneficial for brain health

Foods to avoid for a healthier brain

Apart from adding brain foods to your diet, you might need to exclude some items as well which do not positively impact your cognitive abilities. These items include:

  • Sugary drinks or foods
  • Foods with refined carbohydrates
  • Trans fat-containing dietary options
  • Red meat
  • Aspartame
  • Alcohol
  • Seafood with elevated levels of mercury as well as other heavy metals


The incidence of Alzheimer’s disease has significantly increased over the past decade. Initially, the patient suffers minor changes in perception and comprehension but, as soon as the disease progresses, neurodegeneration speeds up resulting in dementia. Scientists have been working tirelessly, not only to find a treatment for the condition but also to understand its underlining causes. The present article summarizes a recently published study that has indicated the connection between the initiation of Alzheimer’s disease and the alteration in the gut microbiome. Although different brain scanning techniques have been helpful in the diagnosis of AD, this new method of early detection by observing gut bacteria is far more convenient.