Findings in mice offer reason to accelerate research in people; Polyphenols from tea, coca, and colorful plant foods seen as potential allies against Alzheimer’s
by Craig Weatherby
Some four million people in the US suffer from Alzheimer’s and the annual cost of their care is about $100 billion. Sadly, those numbers are expected to triple by 2050.
Given the strictly limited efficacy of current Alzheimer’s drugs, the search for lifestyle measures that could curb the disease is increasingly urgent.
Many epidemiological (population) studies find statistical links between diets high in polyphenol-rich foods and reduced rates of chronic diseases… including Alzheimer’s, cancers, and cardiovascular disease (Singh M et al. 2008).
Polyphenol antioxidants abound in colorful foods such as berries, grapes, extra virgin olive oil, tea, un-Dutched cocoa or dark chocolate, nuts, and whole grains.
(Wild salmon is the only animal food rich in natural antioxidants—specifically, the bright-orange carotenoid compound called astaxanthin. Sockeye salmon—commonly called “red” salmon—offers more of this super-potent antioxidant pigment than other salmon species.)
Growing research boosts food antioxidants as brain allies
And it’s become increasingly clear that polyphenols’ brain benefits extend beyond their antioxidant actions, which reduce the “oxidative stress” caused by free radicals in the brain.
It remains unproven whether polyphenols can cross the human blood-brain barrier in concentrations and forms that actually exert protective effects in people.
However, the links between plant-rich diets and reduced Alzheimer’s rates seen in numerous population studies suggest that they do bring brain benefits, either by direct or indirect means.
Now, an animal study from Spain indicates that diets dominated by antioxidant-rich plant foods could delay the onset of Alzheimer’s disease... at least in mice (Valente T et al. 2009).
The results of this study suggest that in mice, polyphenol antioxidants do two valuable things:
The Spanish team wrote that the outcomes they saw in mice support other indications that diets rich in polyphenols could delay the onset of Alzheimer’s and slow its progress in the brain.
- Stimulate production of new brain cells
- Strengthen the brain’s neural networks
The study consisted of two parts: a feeding study in mice, and a test tube study.
Feeding study finds plant foods spur brain growth
First, the Spanish team divided mice into two groups:
The cream was a mixture of plant-food extracts, including dried fruits and nuts, coconut, vegetable oils, and a flour rich in soluble fiber.
- Standard mouse chow diet (control group)
- Standard mouse chow plus a plant-extracts “cream” high in polyphenols and polyunsaturated fatty acids
We were unable to find the precise fatty acid composition of the cream, but we suspect it was dominated by saturated and omega-6 fatty acids in which coconut and nuts, respectively, abound.
Both groups were fed these diets for 40 days, which corresponds to about five years of human lifespan.
We should assume that the cream was not particularly rich in plant-form omega-3 fats, which abound only in walnuts and flax or hemp seeds, and are less impactful than fish-derived omega-3s.
Compared to the control group fed standard chow, mice that were also fed the custom plant-extracts cream showed more cell growth in their brains’ olfactory bulb and hippocampus… both of which are damaged in patients with Alzheimer’s disease (Valente T et al. 2009).
Test tube study shows plant extracts curb Alzheimer’s process
The Spaniards’ second objective was to see whether the custom cream could prevent oxidative damage caused by free radicals, or prevent the death of brain cells.
Cultures of the animals’ hippocampal and cortical brain cells were pre-treated with the cream.
After causing oxidative damage with hydrogen peroxide, which killed 40 percent of the brain cells, the scientists found that pre-treatment with the plant-extract cream reduced, and in some cases completely prevented, oxidative damage.
And, in an exciting finding, pre-treatment with the plant-extract cream reduced, and in some cases completely prevented, brain cell damage caused by the “rogue” protein (beta-amyloid) that forms the brain plaque characteristic of Alzheimer's disease, which kills brain cells and generates damaging free radicals.
The Spanish researchers say their twin studies indicate that plant-rich diets can help generate new brain cells (neurons) and neuronal networks while protecting brain cells from the causes and kinds of damage associated with Alzheimer's, Parkinson’s, and other diseases affecting the central nervous system.
For more on this subject, see our coverage of past research:
- Bastianetto S, Dumont Y Han Y, Quirion R. Comparative neuroprotective properties of stilbene and catechin analogs: action via a plasma membrane receptor site? CNS Neurosci Ther. 2009 Winter;15(1):76-83. Review.
- Mandel S, Weinreb O, Amit T, Youdim MB. Cell signaling pathways in the neuroprotective actions of the green tea polyphenol (-)-epigallocatechin-3-gallate: implications for neurodegenerative diseases. J Neurochem. 2004 Mar;88(6):1555-69. Review. Erratum in: J Neurochem. 2004 Apr;89(2):527.
- Mandel SA, Amit T, Weinreb O, Reznichenko L, Youdim MB. Simultaneous manipulation of multiple brain targets by green tea catechins: a potential neuroprotective strategy for Alzheimer and Parkinson diseases. CNS Neurosci Ther. 2008 Winter;14(4):352-65. Review.
- Singh M, Arseneault M, Sanderson T, Murthy V, Ramassamy C. Challenges for research on polyphenols from foods in Alzheimer's disease: bioavailability, metabolism, and cellular and molecular mechanisms. J Agric Food Chem. 2008 Jul 9;56(13):4855-73. Epub 2008 Jun 17. Review.
- Valente T, Hidalgo J, Bolea I, Ramirez B, Anglés N, Reguant J, Morelló JR, Gutiérrez C, Boada M, Unzeta M. A Diet Enriched in Polyphenols and Polyunsaturated Fatty Acids, LMN Diet, Induces Neurogenesis in the Subventricular Zone and Hippocampus of Adult Mouse Brain. J Alzheimers Dis. 2009 Aug 3. [Epub ahead of print]
- Vingtdeux V, Dreses-Werringloer U, Zhao H, Davies P, Marambaud P. Therapeutic potential of resveratrol in Alzheimer's disease. BMC Neurosci. 2008 Dec 3;9 Suppl 2:S6. Review.