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Food, Health, and Eco-news
Extra Virgin Olive Oil Protected Livers from Pesticide
by Craig Weatherby

The unstable oxygen molecules called free radicals are often perceived as enemies that accelerate aging and promote chronic diseases.
But free radicals play a role in virtually all of the myriad chemical reactions essential to life.
In healthy people, free radicalsknown medically as reactive oxygen speciesare controlled very effectively by the body's own “antioxidant network,” which includes enzymes, alpha lipoic acid, CoQ10, and vitamins E and C.
However, poor diets and genetic factors can make it hard for the body to control free radicals, and the resulting imbalance can promote major chronic conditionsincluding cardiovascular disease, diabetes, cancer, and Alzheimer's.
Left uncontrolled, free radicals tend to inflict “oxidative damage” on human cells and genes, and exert malign, pro-inflammatory influences on our cells' gene switches (nuclear transcription factors).
Antioxidants in extra virgin olive oil
In cell, animal, and human clinical studies, the tyrosols and other polyphenol compounds found only in extra-virgin grade olive oil (EVOO) display unusually potent antioxidant and anti-inflammatory powers, exceeding those of their cousin compounds in berries and other plant foods.
However, rather than acting as antioxidants in the body, it's increasingly clear that polyphenols exert indirect antioxidant effects through their “nutrigenomic” properties.
The so-called nutrigenomic factors in foodsincluding polyphenolscan throw genetic switches that help control the body's antioxidant and inflammation systems, from “off” to “on” or vice versa.
Fortunately, the polyphenols in plant foods tend to push our gene switches toward beneficial positions.
And as the authors of a new animal study note, growing evidence indicates that EVOO may enhance artery health, reduce the risk of some cancers, and inhibit excessive, damaging inflammation.
(For more on the health effects of EVOOversus refined olive oils, which provide few or no polyphenolssee “Olive Oil Earns More Cardiovascular and Anti-Cancer Kudos,” “Olive Oil Antioxidants Douse Inflammation Genes,” and “Olive Oil Curbs Breast Cancer Gene: Extra Virgin Grade is Best.
Now, a team of scientists from Tunisia and Saudi Arabia report that the polyphenols in EVOO appear to offer substantial protection against oxidative liver damage.
Rat study shows EVOO benefits to liver
The Tunisian-Saudi team tested the effects of feeding EVOOor its water-soluble polyphenolson oxidative damage and liver fatty acids in rats exposed to the free-radical-generating herbicide known as 2,4-D m (Nakbi A et al. 2010).
(By the way, 2,4-D is the third most commonly used herbicide in North America, despite evidence that it may increase the risk of Non-Hodgkin's lymphoma cancer and ALS.)
The researchers separated 80 rats into several groups, all of which were exposed to 2,4-D:
  • A control group given no EVOO.
  • Test groups that were fed whole EVOO, its polyphenol-rich hydrophilic (water) fraction, or its polyphenol-free lipophilic (fatty) fraction.
All of the rats showed some signs of liver damage.
However, the rats fed either whole EVOO or its polyphenol-rich watery fraction displayed two advantages:
  1. Fewer signs of liver damage (lower levels of CD, MDA, and TBARs).
  2. More activity among the body's antioxidant enzymes (SOD, CAT, GPx, and GR).
The first effect probably stemmed from the second, because protection of liver tissues is one of the key jobs of the body's antioxidant enzymes.
And the increased antioxidant enzyme activity effect fits with fast-growing evidence that the polyphenols in plant foods exert nutrigenomic effects, rather than direct antioxidant effects.
(As we've said, food-borne polyphenols display strong antioxidant effects in test tube experiments, but they don't appear to exert direct antioxidant effects in the body… at least not to a substantial extent.)
Confirming that the polyphenols in the EVOO accounted for its observed benefits, the rats that were fed only the polyphenol-poor, fatty fraction of the EVOO suffered substantially greater oxidative damage to their livers.
The researchers concluded that the protective effects of olive oil against oxidative damage are mainly related to the nutrigenomic effects of its polyphenol-rich watery (hydrophilic) components on the body's own antioxidant network.
As they wrote, “The [polyphenol-rich] hydrophilic fraction of olive oil seems to be the effective one in reducing toxin-induced oxidative stress...” (Nakbi A et al. 2010).
Given their findingsand the fact that phenolic antioxidants are metabolized in the liver after being absorbed from the gutthe researchers wisely called for follow-up studies into the liver-guarding effects of food-borne polyphenols.
It's nice to know that a meal made with extra virgin olive oil will blunt the stress on your liver posed by the alcohol in a glass of beer or red wine.
And fortunately, both beverages are packed with polyphenol likely to help EVOO do its liver-loving work!
  • Kasdallah-Grissa A, Nakbi A, Koubaa N, El-Fazaâ S, Gharbi N, Kamoun A, Hammami M. Dietary virgin olive oil protects against lipid peroxidation and improves antioxidant status in the liver of rats chronically exposed to ethanol. Nutr Res. 2008 Jul;28(7):472-9.
  • Nakbi A, Tayeb W, Dabbou S, Issaoui M, Grissa AK, Attia N, Hammami M. Dietary olive oil effect on antioxidant status and fatty acid profile in the erythrocyte of 2,4-D- exposed rats. Lipids Health Dis. 2010 Aug 25;9:89.
  • Nakbi A, Tayeb W, Grissa A, Issaoui M, Dabbou S, Chargui I, Ellouz M, Miled A, Hammami M. Effects of olive oil and its fractions on oxidative stress and the liver's fatty acid composition in 2,4-Dichlorophenoxyacetic acid- treated rats. Nutr Metab (Lond). 2010 Oct 29;7(1):80. [Epub ahead of print]
  • Nakbi A, Tayeb W, Dabbou S, Issaoui M, Grissa AK, Attia N, Hammami M. Dietary olive oil effect on antioxidant status and fatty acid profile in the erythrocyte of 2,4-D- exposed rats. Lipids Health Dis. 2010 Aug 25;9:89.