Scientists examine effects beyond scavenging of free radicals; cell membrane effects cited as key factors behind the benefits of antioxidant pigments in salmon and curry
by Craig Weatherby
Many researchers blame aging on an excess of free radicals… and age-related declines in people’s innate network of enzymes, vitamins, and other antioxidant chemicals.
But two months back, we reported on a study that seemed to undermine the widely accepted idea that free radicals cause or accelerate aging.
Researchers at Montreal’s McGill University published lab results showing that worms actually lived longer when their innate ability to “scavenge” free radicals was partially disabled.
For more on that, see “Worms Weaken Foundations of Radical Theory of Aging.”
However, U.S. researchers who’ve reviewed the literature recently found ample evidence that age-related cognitive decline can be mitigated by diets high in colorful foods, herbs, and spices rich in polyphenol-type antioxidants and omega-3 fatty acids.
Leading examples of such anti-aging super foods include dark leafy greens, walnuts, salmon, cocoa, tea, turmeric, and berries.
How do we explain the discrepancy between the worm study and mountains of evidence in support of dietary antioxidants as anti-aging agents?
The worm study may be partly right… perhaps internal and dietary antioxidants are not the key to slowing aging.
Beyond antioxidants... the myriad roots of plant pigments' powers
An increasing body of evidence indicates that plant “antioxidants” possess other powers that are more important to health and anti-aging.
This evidence consists of direct findings from lab research on cells and in animals, and from epidemiological studies in human populations, which associate antioxidant-rich diets with increased “health span.”
In a review published last August, Daniel Linseman, Ph.D. of the University of Denver noted that a “…significant body of literature…” indicates that free radicals are major factors in the nerve cell death that underlies various neurodegenerative disorders including Parkinson’s disease, Alzheimer’s disease, Huntington’s disease, ALS), and many others.
As he wrote, “…the discovery of novel strategies to mitigate oxidative stress is a principal focus of current therapeutic development programs for neurodegenerative diseases” (Linseman DA 2008).
No doubt that’s true, but it’s looking like plants compounds commonly viewed as antioxidants slow aging, but they may actually do it as much or more by exerting effects in addition to or aside from neutralizing free radicals.
In the April 2009 issue of the journal Mechanisms of Aging and Development, researchers from Ohio State University explained that free radicals generated by inflammation, stress, and environmental toxins damage the membranes of nerve cells, which leads to a decline in cognitive and motor function over time.
The Ohioans went on to say that diet is a key influence on neurological health, with beneficial polyphenol compounds in plants and salmon exerting effects well beyond their antioxidant impacts.
As they wrote, “…polyphenols… and omega-3 fatty acids exert beneficial effects not only through the scavenging of free radicals, but also by modulating signal transduction, gene expression, and restoring optimal neuronal [nerve cell] communication” (Farooqui T, Farooqui AA 2009).
The examples they gave of beneficial polyphenols included flavanols (berries, tea, and cocoa), resveratrol (grapes), curcumin (turmeric), ferulic acid (many plant foods), carotenoids (carrots, peppers, salmon, and other orange-red foods), and quercetin (onions, apples, and many plant foods).
Curcumin found to stabilize cell membranes
For decades, we’ve known that the yellow pigment in turmeric, called curcumin, exerts potent antioxidant and anti-inflammatory effects in cells and animals.
Turmeric has a long history of use in folk medicine for the treatment of wounds, infections, and other health problems, and modern consumers wishing can consume it in supplement form.
Over the last few years, lab and animal research on curcumin has linked the pigment to a range of health benefits, including potential protection against prostate cancer, Alzheimer’s, heart failure, diabetes, and arthritis.
Now, new research shows that the health boosting activity of curcumin may flow from the colorful compound’s ability to stabilize cell membranes and increase cells’ resistance to infection and cancer.
In research supported by funds from the NIH, Ayyalusamy Ramamoorthy, Ph.D. and colleagues at the University of Michigan found that curcumin physically alters the cell membrane at an atomic level (Barry J et al. 2009).
According to Dr. Ramamoorthy, curcumin can induce a negative curvature of the membrane, which would explain the anti-cancer potential of the compound. Other studies have shown that such changes may increase the activity of proteins that play an important role in apoptosis, or programmed cell death.
He and his co-workers reported that molecules of curcumin insert themselves into cell membranes and make the membranes more stable and orderly. This makes the cells more resistant to infection by disease-causing microbes.
The study also revealed that curcumin exerts strong stabilizing effects on the cell membrane structure at low concentrations.
In this sense, curcumin resembles astaxanthin
—the highly potent and colorful carotene-class antioxidant that makes salmon orange
—which is naturally incorporated into the fat layer of the outer cell membrane, thanks to its fat-soluble structure.
Compared to vitamin E and other polyphenols, astaxanthin and curcumin are super-potent antioxidants that also exhibit anti-inflammatory effects.
Both of these antioxidant food factors extend from the outer layer to the inner surface of the cell—the so-called “lipid bi-layer”—a rare characteristic that appears to help protect the cell membrane.
Curried salmon, anyone?
- Willis LM, Shukitt-Hale B, Joseph JA. Modulation of cognition and behavior in aged animals: role for antioxidant- and essential fatty acid-rich plant foods. Am J Clin Nutr. 2009 May;89(5):1602S-1606S. Epub 2009 Apr 1.
- Linseman DA. Targeting Oxidative Stress for Neuroprotection. Antioxid Redox Signal. 2008 Aug 20. [Epub ahead of print]
- Farooqui T, Farooqui AA. Aging: An important factor for the pathogenesis of neurodegenerative diseases. Mech Ageing Dev. 2009 Apr;130(4):203-15. Epub 2008 Nov 21.
- Barry J, Fritz M, Brender JR, Smith PE, Lee DK, Ramamoorthy A. Determining the effects of lipophilic drugs on membrane structure by solid-state NMR spectroscopy: the case of the antioxidant curcumin. J Am Chem Soc. 2009 Apr 1;131(12):4490-8.