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Skriven 2006-10-16 12:52:12 av /m (1:379/45)
Ärende: Food for Thought: Olive Oil's Newfound Benefits
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From: /m <mike@barkto.com>


http://www.sciencenews.org/articles/20061014/food.asp

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Olive oil is a cornerstone of Mediterranean diets, which are renowned for being
good for the heart. Many nutritionists have attributed that benefit to the
oil's high proportion of monounsaturated fatty acids. However, a European study
suggests that olive oil's fatty acid makeup is only part of the story.

The study indicates that lightly processed olive oils—the virgin types common
in Mediterranean diets—offer additional ingredients with a cardiovascular
advantage: abundant antioxidants known as polyphenols.

When healthy men incorporated a virgin olive oil especially rich in these
polyphenols into their diets, characteristics of their blood changed in many
beneficial ways. Before eating polyphenol-rich oil, the men had consumed a diet
low or devoid of the olive antioxidants.

Mar¡a-Isabel Covas of the Municipal Institute for Medical Research in Barcelona
and her colleagues report their findings in the Sept. 5 Annals of Internal
Medicine. The researchers conclude that olive oil "is more than a
monounsaturated fat." The new data are "evidence to recommend the use of
polyphenol-rich olive oil—that is, virgin olive oil"—beyond the benefits
provided by its fatty acids.

Nor is this the only newfound benefit from olive oil. Another European research
team reported this month on a test-tube study showing that compounds in oil
from the skin of olives trigger the death of human-cancer cells.

What is a Mediterranean diet?

Epidemiologic studies have shown that many people from Mediterranean countries
can eat fatty diets and yet not have a high risk of heart disease.

Spaniards José Mataix of the University of Granada and Francisco Javier
Barbancho of the University of Extremadura in C ceres observe in a new book
that the Mediterranean diet "is based on products derived from wheat, olive,
and grape, these constituting the Mediterranean triad of bread, oil, and wine."

In fact, Covas' group points out that several additional features characterize
diets common to the region. Among them: several daily servings of vegetables
and fruits, only a small serving (100 to 150 grams) of red meat per day, few or
no carbonated drinks, at least three weekly meals including shellfish or
legumes, few commercially prepared pastries or sweets, servings of fowl or
rabbit instead of pork or other red meats, and plenty of peanuts and other
nuts.

Some studies have pointed to the alcoholic component as a substantial
contributor of such diets' cardiovascular benefits. However, others have found
that people who drink as much wine and other alcoholic beverages as do
Mediterranean eaters fail to get as many health benefits if they don't follow
the rest of the diet.

For instance, a separate team of all-Spanish researchers that included Covas
recently reported such data in early results from the PREDIMED Study. This
trial is ultimately slated to track for 4 years some 9,000 men and women at
elevated risk of heart disease. Each volunteer is being randomly assigned to
eat a low-fat diet or a higher-fat diet in which much of that fat,
Mediterranean style, comes from either olive oil or nuts, which also are rich
in heart-healthy monounsaturated fats (SN: 11/21/98, p. 328).

In the July 4 Annals of Internal Medicine, Ramon Estruch of the Hospital Clinic
in Barcelona and his colleagues report results from 770 recruits during the
first 3 months of their participation in PREDIMED. People eating either version
of the Mediterranean fare had lower blood glucose concentrations, lower blood
pressures, lower LDL cholesterol concentrations, and fewer markers of
inflammation than did people eating the low-fat diet. All these factors
indicate a reduced risk of heart disease.

Acknowledging that the trial so far is too small and the findings too
preliminary to validate that Mediterranean diets lower heart-disease incidence,
the authors nevertheless point out that data such as these already support the
Mediterranean diet "as a useful tool in managing individuals who are at high
risk for coronary heart disease."

What polyphenols do

In the more-recent Annals of Internal Medicine study, Covas and her team
recruited 200 healthy men, ages 20 to 60. Each man ate the same diet, except
for getting differing types of olive oil for cooking or adding to their food.

The men were randomly assigned to receive 25 milliliters (about 5 teaspoons) a
day of one of three different olive oils: a virgin olive oil containing 366
milligrams of polyphenols per kilogram of oil, a highly refined olive oil with
a polyphenols concentration of just 2 mg/kg, or a mixture of these two oils
with a polyphenol concentration of 164 mg/kg. During each segment of the trial,
the men received a different oil, so that by the end, all had consumed each oil
for one 3-month period. A 2-week "washout" period, during which the recruits
were asked to avoid olives or olive oil, separated trial segments.

The researchers conducted the trial, financed by the European Union, in six
research centers in five European countries: Spain, Denmark, Finland, Italy,
and Germany. Its implications, therefore, shouldn't be confined to any one
ethnic group, say the researchers.

The men's good, or HDL, cholesterol was modestly different—varying by some 1.75
milligrams per deciliter of blood—in the three trial segments, but showed a
clear correlation: highest when they took in the most olive-oil polyphenols and
lowest when they took in the least. Covas calls this trend "the most striking"
of the study.

The new report notes that previous studies by others have shown even a 1 mg/dl
increase in HDL could translate into a 2 to 3 percent reduction in
cardiovascular risk across a treated population.

The polyphenols also appeared to reduce the chemical oxidation of bad, LDL
cholesterol. "Oxidation of LDL is considered a risk factor for coronary heart
disease," notes Covas, a clinical biochemist who focuses on nutrition as a
means to fight heart disease. In this study, the higher the polyphenol content
of the oil, the lower the signs of LDL oxidation in the men's blood.

Concentrations of triglycerides—fats in the blood—decreased with all olive-oil
types, compared with values in the men prior to the trial. This suggests that
this particular effect is attributable to something in olive oil other than
polyphenols.

Antioxidant benefits

Earlier research by Covas' group had also indicated that polyphenols reduce LDL
oxidation. In a study published in the Feb. 15 Free Radical Biology and
Medicine, the researchers recruited a dozen men in their early 20s and had them
eat a breakfast of bread and 40 ml of olive oil on each of three occasions 10
days apart. At each breakfast, the olive oil was different—with a low, medium,
or high concentration of polyphenols. Blood sampled in the hours immediately
after each meal was evaluated to assess whether the LDLs' chemistry and
composition changed from one test day to the next.

The blood tests showed that the men's LDLs picked up olive polyphenols in
proportion to the amounts present in the oil. Moreover, the researchers found
that oxidative stress, as indicated in the men's blood, increased after the
low- and medium-polyphenol breakfast, but not after the breakfast featuring the
high-polyphenol oil.

Olives vs. cancer

Olive oil's benefits appear to extend beyond heart health. For instance, M.
Em¡lia Juan of the University of Barcelona and her colleagues report finding
that triterpenes—waxy hydrocarbons that coat olive skins—shut down the runaway
proliferation of human colon cancer cells.

Juan's team notes that epidemiologic studies have suggested that regular
consumption of olive oil diminishes cancer risk. Although many scientists had
suspected that the fatty acids in olive oil were responsible for the effect,
Juan's team wondered about the possible role of triterpenes.

The researchers isolated the triterpenes from oil and other compounds by
immersing olives for a minute in a solvent. They then purified the compounds
and added them to the growth serum for test-tube colonies of cancer cells.

The extracted chemicals didn't poison the cells, but they did inhibit
proliferation of the cells by triggering them to undergo a natural process of
cell death—something cancer cells typically avoid—the researchers report in the
October Journal of Nutrition.

Moreover, Juan and her colleagues note that concentrations of triterpenes
needed to achieve this effect appear comparable to what

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