Alzheimer's Disease May Result From Past Brain Infections
June 09, 2016
Story at-a-glance
By 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 DiseaseHarvard 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." 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 DamagingIt 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 VirusMany 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 disease to herpes simplex virus 1 (HSV-1), which is the type that causes cold sores. More than 100 studies have been published since supporting the link, but the scientific community has been slow to accept it as a possibility. Itzhaki told Newsweek:3
Earlier this year, Itzhaki and colleagues penned an editorial, published in the Journal of Alzheimer's Disease, that called for increased attention into the role infectious agents play in the progression of Alzheimer's disease, cognitive impairment and other forms of dementia.4 The researchers explained:5
Infectious Prion-Like Protein Also Linked to Alzheimer'sThe accumulating research that suggests Alzheimer's disease may have an infectious component is becoming too plentiful to ignore. In addition to viruses, bacteria and fungus, an infectious protein called TDP-43 has also been linked to the disease. TDP-43 behaves like infectious proteins known as prions, which are responsible for the brain destruction that occurs in Mad Cow and Chronic Wasting Diseases — two types of bovine spongiform encephalopathy. According to research published in 2011, TDP-43 pathology is detected in 25 to 50 percent of Alzheimer's patients, particularly in those with hippocampal sclerosis, characterized by selective loss of neurons in the hippocampus, which is associated with memory loss.6 Research presented at the 2014 Alzheimer's Association International Conference (AAIC) also revealed Alzheimer's patients with TDP-43 were 10 times more likely to have been cognitively impaired at death than those without.7 The common denominator between Mad Cow and Chronic Wasting Diseases (the latter of which affects deer and elk) is forcing natural herbivores to eat animal parts and byproducts, such as blood and bone meal. This is common practice in concentrated animal feeding operations (CAFOs). The evidence also suggests humans may be infected with TDP-43 via contaminated meats. The most infectious parts of a cow carrying these prions are the brain and spinal cord, which may be found in hot dogs, bologna, and products containing either gelatin or ground meat.8 The human version of Mad Cow disease is known as variant Creutzfeldt-Jakob disease (vCJD). Symptoms of vCJD are similar to Alzheimer's and include staggering, memory loss, impaired vision, and dementia,9 and there's no known cure. An intriguing suggestion is that Alzheimer's is a slower moving version of Mad Cow disease, acquired by eating contaminated CAFO meats. Vitamin D Linked to a Lower Risk of Alzheimer'sA wide variety of brain tissue contains vitamin D receptors, and when they're activated by vitamin D, it facilitates nerve growth in your brain. Researchers also believe that optimal vitamin D levels boost levels of important brain chemicals and protect brain cells by increasing the effectiveness of glial cells in nursing damaged neurons back to health. Vitamin D may also exert some of its beneficial effects on your brain through its anti-inflammatory and immune-boosting properties. It also helps produce 200 to 300 different antimicrobial peptides in your body, which kill bacteria, viruses and fungi and could be important if Alzheimer's does turn out to be infectious in nature. Seniors with severe vitamin D deficiency may raise their risk for dementia by 125 percent, and vitamin D deficiency is associated with a substantially increased risk of all-cause dementia and Alzheimer's disease.10 Sufficient vitamin D (50 to 70 nanograms/milliliter) is imperative for overall health, and likely, for brain health as well. Lifestyle Strategies to Prevent Alzheimer's DiseaseThere are an estimated 5.4 million Americans living with Alzheimer's disease, and rates are expected to increase rapidly. By 2050, the number of people age 65 and older with Alzheimer's may reach nearly 14 million, "barring the development of … breakthroughs to prevent or cure the disease," the Alzheimer's Association reported.11 For now, the underlying causes and cures for Alzheimer's are unknown, but there are some lifestyle strategies that may boost your immune system health and significantly lower your risk. Diet is part and parcel of a successful prevention plan, and my optimized nutrition plan can set you on the right path in this regard. In terms of your diet and other lifestyle factors, the following suggestions may be among the most important for Alzheimer's prevention:
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