Can You Prevent Alzheimer Disease with L-Lysine?

Intriguing research suggests that the dementia we call Alzheimer disease may be triggered by a common infection: herpes virus. Although the story is not yet complete, the brain’s immune response to the viral intruder may initiate the development of amyloid beta plaques and tau tangles that are so distinctive. Yet there are hints that antiviral drugs might prevent Alzheimer disease. Could a simple supplement, L-lysine, also help?

Will L-Lysine Ward Off Dementia?

Q. I have a strong family history of Alzheimer disease. If I cannot remember a word or an important date, it scares me half to death.

I have been doing a lot of research on what and what not to do to try and prevent dementia. I recently read that herpes infections might be a contributing factor. This is very worrisome because I have suffered from cold sores for many years.

I have started taking L-lysine to speed healing. It seems to be helping. Do you think it will help prevent dementia?

A. The herpes theory of Alzheimer disease has been kicking around for roughly 40 years. A Canadian pathologist suggested that the herpes simplex virus (HSV-1) that causes cold sores might also be causing “degenerative lesions” within the brain (Canadian Journal of Neurological Sciences, Aug. 1982).

Although this idea languished for decades, researchers are now reconsidering the “Viral Hypothesis and Antiviral Treatment in Alzheimer’s Disease” (Current Neurology and Neuroscience Reports, July 14, 2018).  There are now at least two randomized controlled trials underway to test the antiviral drug valacyclovir (Valtrex) against Alzheimer disease (ACS Chemical Neuroscience, April 7, 2021).

What About L-Lysine?

Valacyclovir is a pharmaceutical, of course, while L-lysine is an amino acid supplement. A retired geriatrician first proposed that this nutraceutical could be used to treat HSV-1 and prevent Alzheimer’s disease (Neuropsychiatry Disease and Treatment, Oct. 27, 2010).  Sadly, scientists have never tested this hypothesis in a clinical trial. As a result, they classify it as “highly speculative.” Without well-controlled clinical trials, clinicians cannot determine whether L-lysine can speed healing of cold sores or help reduce the risk of dementia. You are not the only one wondering about this, however. Read on.

Could L-Lysine Prevent Alzheimer Disease?

Q. Whenever I feel a cold sore coming on (the telltale “tingly feeling”), I take L-lysine tablets. When I take 1000 mg a day, often the cold sore will never develop. If it got a head start, it disappears several days sooner than it would otherwise.

I read your article about herpes and cold sores being linked to Alzheimer’s disease. Is there anything in L-lysine that could be helpful in preventing dementia? I’m going to start taking it every day, maybe 500 mg a day.

No Good Studies of L-Lysine to Prevent Alzheimer Disease:

A. There are few well-controlled long-term studies of the amino acid L-lysine to prevent or treat cold sores (HSV-1 or herpes labialis). A review in the dermatology journal Cutis (July, 2005)  concluded that L-lysine benefits against HSV-1 are unclear. It might help prevent recurrences in selected patients. That said, many readers report success like yours.

There is growing evidence to suggest a link between herpes infection and the risk of developing Alzheimer’s disease (Frontiers in Genetics, Sep. 10, 2018).  A study from Taiwan found that people taking antiviral medicines for herpes were significantly less likely to develop dementia (Neurotherapeutics, April, 2018).

No one knows yet whether L-lysine will prove beneficial. There is, however, some very technical modeling that suggests key lysine residues may help the brain clear itself of certain toxic metabolites (Interdisciplinary Sciences, Computational Life Sciences, Dec. 2019). We’ll be watching for further research to see whether this translates into an ability for L-lysine supplements to prevent Alzheimer disease.