A Step Toward a Dietary Factor in Alzheimer’s Disease?

Drinking 3 or more glasses of fruit juice per week may delay, and possibly moderate, the onset and progression of Alzheimer’s disease. Those are the results of a study conducted by Qi Dai, MD and colleagues at the Vanderbilt (TN)

School of Medicine and published in the September, 2006, issue of the American Journal of Medicine.

The study involved 1,836 participants in the Kame Project(Kame, in Japanese, means “tortoise”), a population-based study of Japanese Americans residing in KingCounty (Seattle), Washington. These participants were free of cognitive defects upon entry into the study between 1992 and1994. The participants were then followed at regular intervals until the study’s conclusion in 2001.

A statistical analysis of the data obtained during the study revealed that those participants that drank at least 3 glasses of fruit and/or vegetable juice per week demonstrated a hazard ratio of 0.24 for the development of Alzheimer’s syndrome as contrasted by a hazard ratio of 0.84 among those that drank less than 3 glasses per week.

Writing in the article’s “Conclusions” section, the group commented that “Growing evidence suggests that oxidative damage caused by the beta-amyloid peptide in the pathogenesis of AD may be hydrogen peroxide-mediated…Many polyphenols, the most abundant dietary antioxidants, possess stronger neuroprotection against hydrogen peroxide than antioxidant vitamins.”

[Author’s Note: “Beta-amyloid peptide” refers to the chemical composition of amyloid plaque, the abnormal substance that is the diagnostic hallmark of Alzheimer’s Disease. As an interesting aside, those born with Down syndrome also exhibit an increase in amyloid plaques as they age but in Down Syndrome the plaques appear at an earlier age.

Polyphenols are chemical substances found to be effective antioxidants. Unfortunately, naturally occurring polyphenols are usually destroyed by food processing. In the Vanderbilt study, the authors note that the currently-touted antioxidant vitamin and nutritional supplements (vitamins C, E, and beta-carotene) did not seem to have the same effects as reported among those who consumed 3 or more glasses of fruit/vegetable juice per week.

Hydrogen peroxide is a powerful oxidizing agent that occurs as an intermediary step in the process of aerobic (in the presence of oxygen) metabolism. Given the brain’s vital dependence on oxygen, it isn’t surprising that hydrogen peroxide’s potential biologic effect on the central nervous system has attracted considerable attention].

However, the authors of the Vanderbilt study reported that only consumption of 3 or more glasses of fruit/vegetable juices per week seemed to affect the subsequent development of Alzheimer’s syndrome. The authors also noted that there was no evidence that the use of antioxidant vitamin supplements had any demonstrable influence on subsequent declines in cognitive ability. The study did demonstrate that the reported reduction of risk for Alzheimer’s syndrome appeared to be most pronounced in those subjects that were also carriers of a specific genetic marker known as the APOE Ã?µ-4 allele. The specific benefits reported among APOE Ã?µ-4 carriers is consistent with results from previous studies, particular those of Peterson et al (2005) and Seshadri et al (1995).

The Vanderbilt study’s authors did note that their results are based on a relatively small population sample and further that their findings will require validation among larger and more ethnically-diverse study populations. However, the reported study is a positive step in understanding the many factors that may contribute to a better understanding of this tragic disease.

Comment

This study is the latest to dispute claims made by those touting the “preventive” effects of “antioxidant vitamin therapy” regarding the onset and clinical course of Alzheimer’s disease. As of this writing (September 2006), the author of this article has yet to read a single reputable report supporting the claims made by these “progressive researchers” and their pseudoscientific “evidence.”

For those interested in following the most recent scientific contributions to understanding of Alzheimer’s syndrome, the author of this article recommends the National Institute of Aging’s Alzheimer’s Information pages.

References

Dai, Q. et al. Fruit and Vegetable Juices and Alzheimer’s disease: The Kame Project. Am J Med 2006; 119:751-759 (Abstract).

Peterson, RC, et al. Vitamin E and Donepezil for the Treatment of MildCognitive Impairment. NEJM 2005; 352:2379-2388 (Abstract).

Seshadri, S et al. Apolipoprotein E epsilon 4 allele and the lifetime risk of Alzheimer’s disease. What physicians know, and what they should know. Arch Neurol. 1995; 52:1074-1079 (Abstract).

Disclaimer

The information presented in this article and its included links is of an informational nature only and is not intended as a recommendation of any changes in the reader’s health care program. Before making any changes in diet, medications, or other treatments the reader is strongly advised to consult with their health care provider.