For those of you who consume capsaicin-loaded foods, there's another positive reason for the burn — it may reduce cognitive decline in Alzheimer's disease and dementia. You heard that right, loading up your food with Scoville units might protect you against Alzheimer's disease.
I've written a lot of articles about the effect of diet on Alzheimer's disease, but this is the first time I've ever written about a spice. I don't know if we have enough evidence to support your carrying a bottle of hot sauce whenever you eat something, but it may not hurt.
As I usually do, I'll review this new systematic review about capsaicin and Alzheimer's disease. I'll tell you about its methodology and whether you need to load up on hot sauce.
What is dementia and Alzheimer's disease?
Before I proceed, it's important to describe what we currently know about Alzheimer's disease (AD). It is a chronic neurodegenerative disease that usually starts slowly and worsens over time. It accounts for 60-70% of dementia cases, even though the terms are sometimes used interchangeably. Alzheimer's disease is a form of dementia. The other forms of dementia include Lewy body dementia, frontotemporal disorders, vascular dementia, and mixed dementia, which is a combination of two or more of the different forms of dementia.
Amyloid plaques (caused by amyloid beta, or Aβ), phosphorylated tau tangles (pTau), and neurofibrillary tangles are generally easily visible pathologies that can be observed by microscopic analysis of brain tissue from autopsies of those potentially afflicted by AD. These plaques and tangles seem to affect nerve functioning. Despite these observations, the precise pathophysiology, or development, of the disease is not known.
Since amyloid plaques are often identified in patients with Alzheimer's disease, a large amount of research is focused on attacking those plaques as a way to reverse the effect on nerves which leads to AD.
The causes of AD are unknown (notice how much we do not know about this disease), although it is speculated that it is mostly genetically related, with a large number of genes that underlie this relationship.
And since we have no clear understanding of the etiology and pathophysiology of AD, there are no effective treatments available today for the disease, although there are some drugs that target the amyloid plaques but have not been shown to change the course or outcomes of AD.
There are a couple of medications that help manage some of the symptoms of the disease, but they are certainly not cures. There are several drugs at the very earliest stages of development that may hold out hope to treat the underlying disease.
One more thing that needs to be made clear. There are no biological tests for Alzheimer's disease — usually, you can only find the amyloid plaques and other pathologies in post-mortem autopsies. Unfortunately. in the absence of an autopsy, clinical diagnoses of AD are "possible" or "probable", based on other findings, such as memory tests and other methods.
In the United States, about 10.7% of seniors (≥65 years) currently have Alzheimer's dementia, and the incidence of dementia and Alzheimer's disease is expected to rise substantially in the coming decades due to population aging, making it imperative to identify modifiable risk factors that may help mitigate its impact. The economic burden of AD is expected to surpass $2.8 trillion by 2030.
What is capsaicin?
Capsaicin is the active compound in chili peppers. It's the compound that gives chili peppers its burning sensation. It is a powerful chemical irritant and neurotoxin.
Chili peppers probably evolved to produce capsaicin as a method to repel mammals that tried to consume the fruit or to inhibit fungal infections. Some animals, such as birds, tolerate the capsaicin and can distribute the seeds widely.
Many domestic chili peppers have been artificially selected for higher levels of capsaicin, making some peppers, such as ghost peppers, have almost intolerably high levels of capsaicin.
Many regional cuisines, such as ones found in Texas, California, Mexico, the Caribbean, and Asia, often have very high levels of capsaicin as part of the base flavor. So, if you live in Los Angeles and partake of all of those foods, maybe you have a lower risk of developing Alzheimer's disease. But let's look at the study before you start eating ghost peppers by the handful.
Capsaicin and Alzheimer's disease paper
In a systematic review published on 15 June 2023 in the International Journal of Molecular Science, Po-Wah So, MD, Department of Neuroimaging, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, and colleagues, examined 11 studies that employed rodents and/or cell cultures to determine the effect of capsaicin on Alzheimer's-associated molecular, cognitive, and behavior changes.
Here are their key results:
- Ten studies showed capsaicin attenuated tau deposition, apoptosis, and synaptic dysfunction; was only weakly effective on oxidative stress; and had conflicting effects on amyloid processing. These biochemical effects are all potentially linked to reducing the underlying mechanisms of Alzheimer's disease.
- Eight studies demonstrated improved spatial and working memory, learning, and emotional behaviors in rodents following capsaicin treatment.
The authors concluded that:
Overall, capsaicin showed promise in improving AD (Alzheimer's disease)-associated molecular, cognitive, and behavioural changes in cellular and animal models, and further investigations are recommended to test the readily available bioactive, capsaicin, to treat AD.
Summary of capsaicin and Alzheimer's disease
Although I found these studies to be fascinating, I need to remind the reader that this data came from animal or cell culture studies. Although almost all clinical research starts with those study models, less than 10% of the time these studies ever amount to anything meaningful from a clinical perspective.
I'd love to recommend to the reader to boost the Scoville units used in their food, but this article is just the beginning. It shows us something, but we need to see clinical or observational data in humans. For example, I'd start with ecological studies that would examine whether cultures that ate higher amounts of capsaicin were linked to a lower incidence of Alzheimer's disease.
For now, this is just an interesting study. But I might put some more hot sauce on my eggs in the morning.
- Inyang D, Saumtally T, Nnadi CN, Devi S, So PW. A Systematic Review of the Effects of Capsaicin on Alzheimer's Disease. Int J Mol Sci. 2023 Jun 15;24(12):10176. doi: 10.3390/ijms241210176. PMID: 37373321; PMCID: PMC10299122.