A diet rich in polyphenol-rich fruit like apples, oranges and bananas may protect against oxidative stress linked to loss of cognitive function and Alzheimer's, suggests a new study.
Extracts from the fruit were tested in an in vitro lab study, which showed a reduction in oxidative stress-induced neuronal cell membrane damage, report Korean researchers in the Journal of Food Science.
"[The new] result clearly demonstrated that PC12 cell death by oxidative stress was suppressed by pretreatment with phenolics," wrote the authors from Gyeongsang National University, Korea University and Kyung Hee University.
Alzheimer's disease (AD) is the most common form of dementia and currently affects over 13 million people worldwide. The direct and indirect cost of Alzheimer care is over $100 bn (€ 81 bn) in the US, while direct costs in the UK are estimated at £15 bn (€ 22 bn).
Although the mechanism of Alzheimer's is not clear, more support is gathering for the build-up of plaque from amyloid deposits. The deposits are associated with an increase in brain cell damage and death from oxidative stress.
It is against the oxidative stress that the anthocyanins and other cabbage polyphenols appear to offer protection.
The researchers used neuron-like PC12 cells and exposed them to fruit extracts at different concentrations (100, 300, 600, 2,000 micrograms per millilitre) prior to treating them with hydrogen peroxide (H2O2) to induce oxidative stress.
Significantly more cells were viable after incubation with the fruit extracts, said the researchers, with apple offering the best protection. Despite this, banana and orange phenolics still protected 118 and 103 per cent more cells, compared to the control, at the highest concentration used.
"Our study demonstrated that antioxidants in the major fresh fruits consumed in the United States and Korea protected neuronal cells from oxidative stress," wrote the authors.
"In addition, it has been reported that apple juice with antioxidative phytochemicals protected brain tissue against oxidative damage, and improved cognitive performance in genetically induced AD mice," they added.
"Therefore, additional consumption of fresh fruits such as apple, banana, and orange may be beneficial to ameliorate chemopreventive effects in neurodegenerative disease such as AD," concluded the researchers.
The results follow hot on the heels of a study from Taiwan's National Chung Hsing University and Food Industry Research and Development Institute, which claimed to be the first to report that the flavanones hesperidin, hesperetin, and neohesperidin from citrus could protect against the toxicity of hydrogen peroxide (H2O2), as well as protecting against DNA damage (Journal of Agricultural and Food Chemistry, doi: 10.1021/jf072826r).
Such is the interest in dietary approaches to improve brain health the world's largest food company, Nestlé, recently signalled its intention to get a head start on the competition with the signing of an agreement in November 2006 with the Swiss Federal Institute of Technology (EPFL) to investigate the role of nutrition in cognitive function.
The agreement with the EPFL, Nestlé's largest collaboration with a university of research institute, will see the company contributing up to CHF 5 million (€ 3.1 million) every year for five years, with a review after four years to potentially extend the project further.
Source: Journal of Food Science
Published online ahead of print, doi: 10.1111/j.1750-3841.2007.00632.x
"Effects of Banana, Orange, and Apple on Oxidative Stress-Induced Neurotoxicity in PC12 Cells"
Authors: H.J. Heo, S.J. Choi, S.-G. Choi, D.-H. Shin, J.M. Lee, C.Y. Lee