From Dr. Mercola:
It’s often stated as fact that Alzheimer’s disease is the result of a buildup of beta-amyloid plaques in your brain. Such plaques may increase in your brain as you age, but tend to be far more abundant in people with Alzheimer’s disease.
Some people have a genetic mutation known to increase the production of beta-amyloid, but in most people the cause behind such buildup is unknown.
Provocative new research suggests that beta-amyloid buildup may not be intrinsically abnormal, and instead, may act as a natural antibiotic that protects your brain from infection. Alzheimer’s disease, then, might be a byproduct of your brain’s attempts to fight off infections.
Alzheimer’s Disease as a Byproduct of Infectious Disease
Harvard researchers have suggested that beta-amyloid proteins are antimicrobial peptides (part of your innate immune response) and have a beneficial role to play in your brain.
If viruses or bacteria cross your blood-brain barrier, the beta-amyloid traps the foreign invader and essentially imprisons it in a sticky beta-amyloid “cage,” where it ultimately dies.
The “cages” left behind form the plaque buildup seen in Alzheimer’s, the researchers suggest. The theory already has some strong scientific backing. So far, the researchers have infected brain cells in petri dishes with bacteria and found beta-amyloid was produced in response.
The experiment was repeated in yeast, roundworms, fruit flies and mice. In the latter case, salmonella infection in the brain led to the development of plaques in the brain’s hippocampus “overnight.”vitami
And according to study author Rudolph E. Tanzi, Ph.D., of Harvard Medical School and Massachusetts General Hospital, “each plaque had a single bacterium at its center.”1 Mice that didn’t produce beta-amyloid were at greater risk of dying from the infection and did not have any plaques in their brains.
Beta-Amyloid May Be Both Protective and Damaging
It could be that a little bit of beta-amyloid is protective, while larger amounts lead to damage. You may develop more beta-amyloid plaques as you get older because your blood-brain barrier tends to become “leaky” with age, allowing the opportunity for more pathogens to enter your brain.
Separate research by Dr. Berislav Zlokovic, the director of the Zilkha Neurogenetic Institute at the University of Southern California, has shown that the leakiest area of the blood-brain barrier is near the hippocampus, where plaques typically form in Alzheimer’s disease.2
Even brain infections that caused no symptoms could potentially lead to the buildup of plaques, which may explain why some people with no known history of brain infections go on to develop Alzheimer’s.
It’s also likely that people have varying abilities to clear the plaques from their brains after infection. Part of this may be genetically based and there are likely other factors involved as well.
Alzheimer’s Previously Linked to Herpes Virus
Many are not aware that Alzheimer’s disease has been linked to viral infections in the past. In 1991, Ruth Itzhaki, Ph.D., professor emeritus of molecular neurobiology at Britain’s University of Manchester, and colleagues first linked the