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Oysters to Prevent Alzheimers? Zinc Imbalance Plays Role in Memory Loss

zinc, alzheimer's disease, memory, nutrition

Zinc is an essential nutrient involved in many aspects of cellular metabolism. In the body, the highest levels of zinc are found in the brain. New research finds that zinc deprivation may be involved in the progression of memory loss associated with Alzheimer’s disease.

The brains of Alzheimer’s patients have two types of lesions: beta-amyloid plaques outside the neurons and neurofibrillary tangles within. Although the plaques do interrupt brain cell communication, it is the tangles comprised of tau protein which are more closely correlated with Alzheimers disease symptoms. The tau proteins are normally adhered to microtubules, but new research finds that a zinc imbalance may disrupt this normal pathology leading to memory loss.

A team of researchers from Harvard University, Boston University, The University of Alberta, The University of Arizona, and The Chopra Foundation came together to study the association between the mineral zinc and Alzheimer’s disease. Dr. Rudolph Tanzi of Harvard had previously found that plaques outside neurons sequester zinc which in turn lowers the levels inside the neurons.

For the new study, the researchers dig deeper into the role of zinc within the microtubules (MTs) of the brain. These structures are polymers of tubulin, a globular protein. Mts regulate synapses, the spaces between brain cells. Zinc binds to tubulin and is critical to the polymer structure of the MT. The highest levels of zinc are found in the hippocampus, the portion of the brain responsible for memory formation.

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Dietary zinc deprivation affects zinc homeostasis in the brain. In children, insufficient levels of zinc have been associated with lowered learning ability and mental retardation. But even in adults adequate zinc supply is important for brain functions and prevention of neurological diseases.

The Recommended Dietary Allowance for zinc for adults is 11 milligrams per day for men and 8 milligrams for non-pregnant, non-lactating women. Oysters contain more zinc per serving than any other food, but red meat and poultry provide the majority of the zinc in the typical American diet. Other good food sources include beans, nuts, certain types of seafood (such as crab and lobster), whole grains, fortified breakfast cereals, and dairy products.

What about zinc supplements? Two major national surveys have found that most Americans easily meet their need for zinc with a healthy balanced diet– important because the body has no storage system for the mineral. However, if zinc deficiency is found, a physician can recommend the appropriate amount for supplementation.

The findings of the new study are exciting for Alzheimer’s research because it presents a new approach to therapies for the disease that is the most common form of dementia and a leading cause of death in the elderly. Dr. Tanzi said, “Protecting microtubules and their association with tau may be the best treatment approach in Alzheimers disease.”

Journal Reference:
Craddock TJA, Tuszynski JA, Chopra D, Casey N, Goldstein LE, Hameroff SR, Tanzi RE (2012) The Zinc Dyshomeostasis Hypothesis of Alzheimer's Disease. PLoS ONE 7(3): e33552. doi:10.1371/journal.pone.0033552

Additional Resources:
Pfeiffer CC, Braverman ER. Zinc, the brain and behavior. Biol Psychiatry. 1982 Apr;17(4):513-32.
Takeda A. Zinc homeostasis and functions of zinc in the brain. Biometals. 2001 Sep-Dec;14(3-4):343-51.
Khalid Iqbal et al. Defective Braiin Microtubule Assembly In Alzheimer’s Disease. The Lancet, Volume 328, Issue 8504, Pages 421 - 426, 23 August 1986 doi:10.1016/S0140-6736(86)92134-3
Duke Health (Duke University) Zinc Regulates Communication Between Brain Cells
Office of Dietary Supplements (National Institutes of Health)