Could Alzheimer’s Be Caused by a Microbe?

By Kelley Herring

For many years, the scientific research has clearly demonstrated a connection between chronically high-blood sugar and the development of Alzheimer’s disease. In fact, the role of metabolic dysfunction is so well established that some doctors refer to Alzheimer’s as “Type 3 Diabetes.”

But as with most chronic illness, the factors that can cause disease are many and varied. And very often what happens in the gut also plays a starring role. So, it should come as no surprise that researchers now believe there is a strong connection between impaired gut health and the development of Alzheimer’s.

Today, we look at startling new research that points to specific microbes linked to developing cognitive impairment. Plus, we discuss the unique diet found to target these potentially harmful organisms, improve cognition and reduce the risk of Alzheimer’s.

Your Microbiome and Disease Risk

You probably already know that a healthy gut contains a diverse balance of bacteria. And this is important because the type of microbes you host can contribute to everything from diabetes and cancer, to Parkinson’s and autoimmune disorders.^1,2,3

“For a long time, scientists assumed that these bacteria, despite their numbers, neither did us much harm nor much good. But in the past decade or so, researchers have changed their tune.”

 – Scientific American

And while most research focuses on the bacteria in the gut, there’s another important class of microbes that is often overlooked: Fungus!

In fact, the populations and types of fungi in your gut (called the mycobiome) have just as big an influence on disease risk as bacteria do.

For example, research shows people with Crohn’s disease have more fungi and fewer bacteria in their guts than people without the disease. What’s more, Crohn’s disease flare-ups can be linked to a surge of fungi in the gut.^4,5

And according to a recent study conducted at Wake Forest, fungi in your gut could even play a role in your risk for Alzheimer’s!

The Link Between Gut Fungus & Mild Cognitive Impairment

In a randomized, double-blind pilot study, researchers evaluated 17 older adults, 11 of whom were diagnosed with mild cognitive impairment (MCI) – a precursor to Alzheimer’s disease.

By sequencing the fungal rRNA ITS1 gene, researchers were able to identify the specific organisms in the gut microbiomes of the subjects. Researchers sequenced this gene twice during the study: First, at the beginning of the trial and then six weeks after starting either the Mediterranean ketogenic diet or the low-fat American Heart Association Diet.

The researchers also extracted and analyzed the participants’ cerebrospinal fluid (CSF) to assess specific markers for Alzheimer’s.

What they discovered is that certain families of fungi were far more abundant in the guts of people with mild cognitive impairment those without it. What’s more, the presence of these fungi was also linked to markers for Alzheimer’s disease in the samples of cerebrospinal fluid.

The researchers concluded that these fungi have the ability to increase Alzheimer’s risk, but specific dietary interventions can make a big difference.

Principal investigator of the study Hariom Yadav says:

“Although we do not fully understand how these fungi contribute to Alzheimer’s disease, this is the first study of its kind to reveal their role in our mental health, which we hope will ignite thinking in the scientific community to develop a better understanding of them in relation to Alzheimer’s disease… It also indicates that dietary habits such as eating a ketogenic diet can reduce harmful fungi in the gut which might help reduce Alzheimer’s disease processes in the brain.”⁶

Not surprisingly, the low-fat American Heart Disease Diet – which contained 50-60% carbohydrate – did not reduce the fungal colonies associated with mild cognitive impairment (MCI). This makes sense as fungus thrives in the presence of carbohydrate.

Target Cognitive Impairment with the Mediterranean Keto Diet

To beneficially shift the fungal populations in the gut, researchers used a modified Mediterranean ketogenic diet (MMKD) containing no more than 20 grams of carbohydrates daily. The diet also included liberal amounts of extra virgin olive oil, along with meats, fish and low-carb, nutrient-dense veggies.

Here’s a sample of what a day on this diet might look like:

• Poached Eggs with Avocado

• Wild Salmon Salad with Artichokes & Olives, dressed with a Lemon-Olive Oil Vinaigrette

• Raw almonds, grass-fed cheese, grass-fed beef jerky

• Pasture-Raised Pork Chops with Sauteed Red Cabbage and Asparagus

In addition to addressing fungal imbalances with a keto diet, several well-known supplements with anti-fungal properties may also help. These include caprylic acid, monolaurin and undecylenic acid (primarily derived from coconut). As always, talk with your natural-minded health care practitioners before starting any new diet or supplement.

Read more of Kelley Herring’s health and wellness articles on our Discover Blog. 

References

1 Hasegawa, S. et al. Intestinal Dysbiosis and Lowered Serum Lipopolysaccharide-Binding Protein in Parkinson’s Disease. PLOS One. 2015;10(11):e0142164.

2 Junjie Qin,Yingrui Li,  Zhiming Cai. A metagenome-wide association study of gut microbiota in type 2 diabetes. Nature  490, 55–60 (04 October 2012) doi:10.1038/nature11450

3 Storoni M1, Plant GT1. The Therapeutic Potential of the Ketogenic Diet in Treating Progressive Multiple Sclerosis. Mult Scler Int. 2015;2015:681289. doi: 10.1155/2015/681289. Epub 2015 Dec 29.

4 Miyoshi J, Sofia MA, Pierre JF. The evidence for fungus in Crohn’s disease pathogenesis. Clin J Gastroenterol. 2018 Dec;11(6):449-456. doi: 10.1007/s12328-018-0886-9. Epub 2018 Jul 19. PMID: 30027368.

5 G. Hoarau, P. K. Mukherjee, C. Gower-Rousseau, et al. Bacteriome and Mycobiome Interactions Underscore Microbial Dysbiosis in Familial Crohn’s Disease. mBio Sep 2016, 7 (5) e01250-16; DOI: 10.1128/mBio.01250-16

6 Nagpal R, Neth BJ, Wang S, Mishra SP, Craft S, Yadav H. Gut mycobiome and its interaction with diet, gut bacteria and alzheimer’s disease markers in subjects with mild cognitive impairment: A pilot study. EBioMedicine. 2020 Sep;59:102950. doi: 10.1016/j.ebiom.2020.102950. Epub 2020 Aug 30. PMID: 32861197; PMCID: PMC7475073.