The Gut Microbiome and Alzheimer’s Disease

August 19th, 2022 | Posted in Info

The Gut Microbiome and Alzheimer’s Disease

The human gastrointestinal tract is home to a diverse and dynamic population of microorganisms known as the gut microbiota or the microbiome. The microbiome influences many organs and body systems beyond the gut, including the brain via the gut-brain axis.

Recent evidence has found that the gut microflora play a role in the bidirectional communication between the gut and the brain.  It is suggested that the gut microflora act as a “second brain” and may play a key role in neurodegenerative disorders. Many studies appear to confirm the relationship between Alzheimer’s disease and the gut microbiota.

The gut microbiota may be altered by factors such as ageing, antibiotics and other drugs, diet, lifestyle, geographical location and environmental toxins such as pesticides. These factors often lead to gastrointestinal disturbances as well as central nervous system disorders such as Alzheimer’s.


Dysbiosis of gut microbiota can induce increased intestinal permeability, systemic inflammation and neuro-degeneration. This may lead to the development of AD pathologies and cognitive impairment via neural, immune, endocrine, and metabolic pathways. Thus, the modulation of gut microbiota through diet and oral bacteriotherapy may induce beneficial effects on neuronal pathways leading to a delay in the progression of Alzheimer’s disease (1).

Poor dietary habits and ageing, along with inflammatory responses due to dysbiosis, may contribute to the pathogenesis of AD. Here are some possible strategies for modulating the make up of the gut microbiome in order to affect brain health and possibly prevent or slow the progression of Alzheimer’s Disease:

Diet – research suggests that specific gut microbial signatures may be implicated in cognitive impairment and that eating a ketogenic Mediterranean diet may modulate the gut microbiome and metabolites in a way that is associated with improved biomarkers of AD in the cerebrospinal fluid (2).

Prebiotics and Probiotics – probiotic and prebiotic rich foods and supplements can be used to modify gut microbial composition. This may be a possible preventive/therapeutic option for AD (3,4). Probiotic and prebiotic foods include sauerkraut, yoghurt, kefir, kimchi, kombucha, cider vinegar, sourdough bread, tempeh and miso.

Faecal microbial transplantation – could be a potential therapeutic intervention in AD (5). This is when microbes from a healthy person are transplanted into the bowels of patients with dysbiosis in the hope that they will colonise the bowels and transform the make up of the microbiome.

Antibiotics and Alzheimer’s

Antibiotics are normally used to remove or prevent bacterial colonisation in the human body. However, they do not usually target specific types of bacteria. As a result, broad-spectrum antibiotics can have a lasting impact on the gut microbiota, reducing its biodiversity, and delaying re-colonization for a long time after administration. There is a hypothesis that using custom made antibiotics in a targeted way could alter the gut microbiome in a way that alters brain activity (6). Herbal antibiotics have long been used to affect gut health. The use of herbs in the treatment of Alzheimer’s could be a rich seam of research.

See blog posts Diet to Prevent Dementia and Healthy Habits to Prevent Dementia for ideas on what to eat and how to live to prevent dementia.


1. Prog Neuropsychopharmacol Biol Psychiatry. 2021 Mar 2;106:110112. Emerging role of gut microbiota in modulation of neuroinflammation and neurodegeneration with emphasis on Alzheimer’s disease. Goyal D et al.

2. 2019 Sep;47:529-542. Modified Mediterranean-ketogenic diet modulates gut microbiome and short-chain fatty acids in association with Alzheimer’s disease markers in subjects with mild cognitive impairment. Nagpal R et al.

3. Life Sci. 2021 Jan 1;264:118627. Role of gut-brain axis, gut microbial composition, and probiotic intervention in Alzheimer’s disease. Kesika P et al.

4. Aging (Albany NY). 2020 Mar 19;12(6):5539-5550. Gut microbiota and pro/prebiotics in Alzheimer’s disease. Pluta R et al.

5. 2021 Feb 21;13(2):690. Crosstalk between Gut and Brain in Alzheimer’s Disease: The Role of Gut Microbiota Modulation Strategies. Shabbir U et al.

6. J Neuroinflammation. 2019 May 22;16(1):108. Antibiotics, gut microbiota, and Alzheimer’s disease. Angelucci F et al.