Candida albicans is a very common yeast infection that has now been shown to cause brain abnormalities that are very similar to dementia and Alzheimer's disease. Candida yeast microorganisms are normally in symbiosis with the human mouth, gut, skin and mucous membranes and genital tract - meaning that they are a normal part of our micro biome. Usually they are harmless but infections like thrush can and do occur from time to time. This yeast is the most common fungal infection affecting humans.
A new study in Nature Communications1 (Nature Communications, volume 10, Article number: 58 (2019)) shows that Candida albicans can pass through the blood brain barrier and lead to inflammation in the brain which in turn leads to memory impairment. Although this study was performed in mice, the study is very interesting since it makes a direct link between fungal infection, respiratory illness and cognitive decline such as dementia.
Water damaged and mouldy homes are well known to display Candida-type yeasts along with other moulds like Aspergillus, Cladosporium, Stachybotrys, Fusarium, Alternaria and Penicillium sp. For example in India, nearly 5% of the total airborne fungal types identified (their CFU/m^3 and average percent contribution) were from Candida albicans2. As well, exposure to Candida can occur from drains in kitchens and bathrooms and laundries3. A further study4 into water-based spread of fungi has also shown a positive correlation in dentistry where the water used to operate dental equipment was shown to be contaminated with biofilms of Candida and other fungi. This means that persons who live or work in such environments are potentially more likely to be exposed to yeasts above levels they would be expected to encounter in dry (non mould affected) buildings and workplaces.
In the Nature study, the mice were dosed with just enough yeast to affect the brain but not enough to cause disease like sepsis. At this much lower concentration, the yeast entered the brain and caused the brain microglia to activate. The microglia are a type of immune cell. Ameloid plaques soon developed in the mouse brains dosed with Candida. The scientists tested memory and found that spatial memory was reduced in the Candida-infected mice. This resolved when the infection cleared.
"the results prompted us to consider the possibility that in some cases, fungi also could be involved in the development of chronic neurodegenerative disorders, such as Alzheimer's, Parkinson's, and multiple sclerosis. We are currently exploring this possibility."
The big take-away from this landmark study is that exposure to Candida albicans could cause cognitive decline also in humans. This is because as much as 0.7% of the global land-surface is covered in buildings3 and building decay/dilapidation, condensation and plumbing failures all contribute to conditions that favour mould and yeasts. This is yet one more reason to test for yeasts and mould in your home or office.
- Wu, Y., Du, S., Johnson, J.L., Tung, H-Y., Landers, C.T., Liu, Y., Seman, B.G., Wheller, R.T., Costa-Mattioli, M., Kheradmand, F., Zheng, H. & Corry, D.B. (2019). Microglia and amyloid precursor protein coordinate control of transient Candida cerebritis with memory deficits. Nature Communications, volume 10, Article number: 58 (2019). https://doi.org/10.1038/s41467-018-07991-4
- Kochar, S., Aslawat, M., Dahiya, P. and Chaudhry, D. (2014). Assessment of allergenicity to fungal allergens of Rohtak city, Haryana, India. Allergy & Rhinology. Summer 2014, Vol. 5, No. 2. e56-e65. doi: 10.2500/ar.2014.5.0088
- Adams, R.I., Miletto, M., Taylor, J.W and Bruns, T.D. (2013). The diversity and distribution of fungi on residential surfaces. PLOS ONE. 2013 Nov 1;8(11):e78866. https://doi.org/10.1371/journal.pone.0078866
- Damasceno, J.L., Dos Santos, R.A., Barbosa, A.H., Casemiro, L.A., Pires, R.H. and Martins, C.H.G. (2017). Risk of Fungal Infection to Dental Patients. Scientific World Journal. 2982478. doi: 10.1155/2017/2982478