A recent paper (1) published by Dr.
Chopra's research group at the Northern Ireland Center for Diet and Health,
University of Ulster, had some interesting conclusions.
Health benefits from lycopene in tomato products have been
suggested to be related to its antioxidant activity. Dietary fat may influence
the absorption and hence the antioxidant activity of lycopene. The study
compared the effect of consumption of tomato products with extra-virgin olive
oil versus sunflower oil. The different oils did not affect the absorption of
the lycopene into the body, but the tomato/olive oil combination generated
increased plasma antioxidant activity by around 20%. Therefore one conclusion
drawn from the research was that it would seem that consumption of tomato
products with olive oil, but not with sunflower oil, improves the antioxidant
activity of the plasma.
Researchers are faced with the question of whether the
combination of tomato and olive oil does something synergistically, or whether
the beneficial antioxidant effects are caused by olive oil alone. Extra virgin
olive oil is particularly rich in the phenolic antioxidants as well as squalene
and oleic acid, and high consumption of the foregoing in the diet provides
considerable protection against colon, breast and skin cancer, coronary heart
disease and aging by inhibiting oxidative stress. Research has shown that
scavenging of the hydroxyl radical was significantly higher among extracts of
olive oil. This effect was only minimal in seed oils. In addition to their
direct antioxidant capacity, extracts of olive oil are also potent inhibitors of
xanthine oxidase activity. A constant high olive oil intake in the diet,
especially extra virgin olive oil, provides a constant supply of antioxidants.
This may reduce oxidative stress through inhibition of lipid peroxidation, a
factor that is currently linked to a host of diseases such as cancer and heart
disease.
There is a low incidence of skin cancer among Mediterranean
populations, and olive oil consumption could be a contributing factor to this
low cancer rate. Olive oil contains significantly higher amounts of squalene
than seed oils, and squalene is to a large extent transferred to the skin.
German researchers believe that this transfer mechanism is probably accomplished
by scavenging singlet oxygen generated by ultraviolet light. Japanese scientists
also claim that virgin olive oil applied to the skin after sunbathing could
protect against skin cancer by slowing tumor growth.
Researchers at the University Hospital "Germans Trias
Pujol" in Barcelona, Spain, compared the benefits of olive oil with
safflower and fish oil on rats to determine if the type, and not just the
amount, of fat in the diet had an impact on cancer tumor growth. They found that
the research subjects on the olive oil diet had less precancerous tissue and
fewer tumors than the animals fed the other oils.
The researchers believe constituents of olive oil, such as
flavonoids, squalene and polyphenols, may help to protect against cancer.
Flavonoids and polyphenols are antioxidants, which help prevent cell damage from
oxygen-containing chemicals called free radicals.
Another study by researchers at the University of Oxford adds
to the growing body of evidence that shows olive oil is as effective as fresh
fruit and vegetables in keeping colon cancer at bay.
Dr Michael Goldacre and a team of researchers at the
Institute of Health Sciences compared cancer rates, diets and olive oil
consumption in 28 countries including European countries, the United States,
Brazil, Colombia, Canada and China. Countries with a diet high in meat and low
in vegetables had the highest rates of the disease and olive oil was associated
with a decreased risk.
The researchers suspect olive oil protects against bowel
cancer by influencing the metabolism of the gut. They think it cuts the amount
of a substance called deoxycyclic acid and regulates the enzyme diamine oxidase
which may be linked to cell division in the bowel.
A study in the March 27, 2000 issue of Archives of Internal
Medicine, which was produced by Dr. Ferrara's research team, shows that a diet
high in MUFA from olive oil can also help reduce blood pressure levels.
Ferrara and his colleagues found that while consuming the
extra-virgin olive oil diet, research subjects reduced the amount of
antihypertensive medication necessary to control blood pressure levels by 48%,
versus only a 4% reduction on the sunflower oil diet. In addition, eight
subjects on the extra-virgin olive oil diet required no antihypertensive
medications; all subjects on the sunflower oil diet required antihypertensive
medication. The authors conclude that a diet lower in total fat and saturated
fat and a diet that contains higher amounts of MUFA can lower blood pressure
levels and reduce or eliminate the need for medications in people with
hypertension.
So why does olive oil lower blood pressure? One possible
reason is its polyphenol content. Polyphenols are potent antioxidants which help
arteries dilate, thereby reducing blood pressure. Ten grams of extra-virgin
olive oil contains five mg of polyphenols; sunflower oil has no polyphenols.
Constantine Alexander
Certified Olive Oil Consultant
(1)
Lee, A.; Thurnham, D.I.; Chopra, C. Consumption of Tomato Products with Olive
Oil but not Sunflower Oil increases the Antioxidant Activity of Plasma. Free
Radical Biology & Medicine, 29:1051-1055; 2000 [Nov. 15th, 2000 issue]
http://www.eat-online.net/english/education/olive_oil/health_benefits.htm