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June 2005

Quercetin Protects Nerve Cells from Oxidation

Quercetin, a bioflavonoid found in many fruits and vegetables, may protect nerve cells from the oxidative damage associated with conditions like Alzheimer’s disease, report investigators at Cornell University.*

The human central nervous system is highly sensitive to oxidative stress, making it vulnerable to neurodegenerative diseases such as age-related cognitive decline and Alzheimer’s. Scientists have studied many antioxidants, including vitamin C, as potential therapeutic agents against neurodegeneration. The Cornell group has now demonstrated that quercetin is better than vitamin C at protecting nerve cells from damage due to oxidative stress.

In their study, the Cornell researchers used a cell line with nerve-like characteristics. The cells were pre-incubated for two hours with either quercetin or vitamin C, and the treated cells were then exposed to hydrogen peroxide, a significant inducer of oxidative damage. Quercetin was more protective than vitamin C, and less cell death occurred in the quercetin-treated cells than in those treated with vitamin C. Quercetin also protected nerve cell membranes more than did vitamin C. This is significant because the researchers believe that loss of cell membrane integrity contributes to neurotoxicity. Larger doses of quercetin or vitamin C conferred greater protection from oxidative stress.

These findings suggest that quercetin offers significant antioxidant protection to nerve cells. Quercetin may therefore help to prevent or manage Alzheimer’s disease and other neurodegenerative conditions associated with oxidative stress.

—Linda M. Smith, RN


Heo HJ, Lee CY. Protective effects of quercetin and vitamin C against oxidative stress-induced neurodegeneration. J Agric Food Chem. 2004 Dec 15;52(25):7514-7.

DHEA Improves Cardiovascular Health

DHEA (dehydroepiandroste-rone) improves blood flow and other measures of vascular health, report researchers at Australia’s Monash University.*

Epidemiological studies have linked age-related decline in DHEA levels with decreased longevity and an increased risk of heart disease. The Australian team’s findings, published in the Journal of Clinical Endocrinology and Metabolism, help elucidate the mechanisms by which DHEA benefits the cardiovascular system.

Using in-vitro studies, the investigators demonstrated that DHEA, like estrogen and testosterone, stimulates endothelial cells to divide. The endothelial cells lining blood vessels are critically important in cardiovascular health, as injury to such cells leads to the formation and progression of atherosclerotic plaque. DHEA expands the endothelial cell pool, possibly providing a ready source of cells able to “patch” areas of blood vessel injury. Additionally, DHEA provoked endothelial cells to produce greater amounts of nitric oxide, a vasodilator and powerful protector of the heart and blood vessels. DHEA exerted its effects on endothelial cells independently of both estrogen and androgen receptors.

The researchers also administered 100 mg per day of DHEA to 36 healthy postmenopausal women for three months. Using measures of blood vessel function, they showed that DHEA increased blood vessel dilation and reduced blood pressure. Moreover, DHEA supplementation led to increased blood flow and reduced cholesterol levels.

DHEA appears to be both safe and effective in improving cardiovascular health. Its mechanisms of action include optimizing blood flow, blood pressure, and cholesterol, in addition to supporting the health of endothelial cells. As DHEA supplements may be contraindicated in those with a history of hormone-related cancer, always consult with your physician before considering supplementation.

—Linda M. Smith, RN


* Williams MR, Dawood T, Ling S, et al. Dehydroepiandrosterone increases endothelial cell proliferation in vitro and improves endothelial function in vivo by mechanisms independent of androgen and estrogen receptors. J Clin Endocrinol Metab. 2004 Sep;89(9):4708-15.

Berry Extracts Help Prevent Ulcers

Berry extracts help kill the bacteria that cause most ulcers and improve the efficacy of prescription ulcer therapy, according to a report from Creighton University in Omaha, NE.*

Helicobacter pylori (H. pylori), a bacteria that infects the stomach and small intestine, is associated with up to 90% of cases of peptic ulcer disease, as well as with gastric carcinoma and one type of lymphoma. H. pylori may also be linked to gastroesophageal reflux disease, or heartburn. Conventional treatment of H. pylori employs antibiotics combined with an inhibitor of acid secretion and/or a bismuth compound. Treatment failure is common, due either to difficulty in adhering to the complex medication regime or to the bacteria’s resistance to antibiotics.

The Nebraska researchers demonstrated that berry extracts not only inhibit the growth of H. pylori, but also render it more susceptible to clarithromycin, one of the antibiotics used to eradicate the bacteria. H. pylori bacteria were incubated with extracts of raspberry, strawberry, cranberry, elderberry, blueberry, or bilberry, or with a combination of all six berries, for 18 hours. The mixture was then incubated with clarithromycin for an additional hour prior to growth assessment on Petri plates. All of the berry extracts inhibited H. pylori growth and increased its sensitivity to clarithromycin better than controls. The combined extracts exhibited greater potency than did the individual berry extracts.

Because of the serious nature of its associated medical conditions, anyone who tests positive for H. pylori should seek treatment. The Nebraska study suggests that the use of non-antibiotic supplements such as berry extracts improves the efficacy of antibiotic treatments.

—Linda M. Smith, RN


* Chatterjee A, Yasmin T, Bagchi D, Stohs SJ. Inhibition of Helicobacter pylori in vitro by various berry extracts, with enhanced susceptibility to clarithromycin. Mol Cell Biochem. 2004 Oct;265(1-2):19-26.