Nov. 13, 2004
The
volunteers consumed gazpacho, a Mediterranean-style
cold soup of uncooked
vegetables.
It contained generous amounts
of tomatoes, which are rich in vitamin C, along with
peppers, cucumbers, onions, garlic, oil, and seasonings.
Many studies
have shown that vitamin C is a potent antioxidant that
counters damage to human cells and tissues caused by
highly reactive
molecules called free radicals. But this study indicates
that "the
protective effect of vegetables may extend beyond their antioxidant
capacity," says lead investigator Antonio Martin.
The results,
he says, point to other important functions of vitamin C at
the molecular level. These functions include a major role in
preventing the formation of compounds involved in abnormal
inflammation and a biochemical process called oxidative stress,
both of which can alter cells in ways that set the stage for
chronic diseases.
People probably don't have to consume vegetables
in the form of a soup to get the benefits seen in the study,
Martin and his colleagues note in the November Journal
of Nutrition.
They don't rule out, however, that additional nutrients in
the particular mix of vegetables used in the gazpacho may provide
a synergistic effect.
They fed the volunteers the prepared
soup, they explain, because "it's a simple way to ingest generous
amounts of vegetables." Gazpacho is a popular food in Spain,
Martin's native country.
His team recruited 12 volunteers,
half men and half women. All were in their early 20s and none
had a major health problem. The participants maintained their
usual lifestyles and ate as they normally would, except for
the bonus soup. None of them took vitamins and minerals or
medications before or during the study.
Before the volunteers
began the twice-daily soup regimen, the researchers collected
blood samples from them and measured concentrations of vitamin
C as well as several compounds that indicate inflammation and
oxidative stress.
The gazpacho was prepared in a home-style
blender, then vacuum packed in individual portions. The volunteers
consumed a total of 17 ounces of the soup every day for 14
days. The researchers collected blood samples again on the
7th and 14th days of the study.
The results showed that as
of the 7th day, the amount of vitamin C in the volunteers'
blood increased by 26 percent for the men and 25 percent for
the women. The concentrations remained elevated during the
final week of the study.
Less
stress
The researchers
also measured blood concentrations of several molecules
that the body secretes
in response to stress. High readings for these molecules
can indicate increased vulnerability to various illnesses
because
stress molecules, such as various hormonelike prostaglandins,
induce inflammation and oxidative stress. Inflammation
normally aids the repair of injured tissue as part of
the body's infection-fighting
defenses, but when a person's internal regulatory
mechanisms are faulty, systemic low-grade inflammation
can cause
progressive damage.
After a week of consuming the soup
consistently, the
volunteers had a significant decrease in blood concentrations
of prostaglandin E2, which is produced during inflammation
and influences immune responses.
The young men and
women also had lowered their amounts of two other stress
markers: a particular
isoprostane molecule that increases with age and
in chronic diseases, and a molecule called monocyte chemotactic
protein-1,
which has been found in high concentrations in artery-clogging
plaques that pave the way to heart disease.
The blood
concentrations of these three compounds dropped inversely
in proportion to
the increase of vitamin C concentrations in the volunteers'
blood. This clear inverse correlation, the researchers
say, suggests that the vitamin C gave strong protection
against
the damaging effects of inflammation and oxidative
stress.
Moreover, the volunteers had decreased amounts
of uric acid
in their blood. A buildup of uric acid causes the
joint
inflammation called gout. Research suggests that high
amounts of uric acid
may also contribute to the development of vascular
dysfunction and heart disease by impairing some cells
that line blood vessels.
In this study, uric acid concentrations were 18 percent
lower in the male volunteers and 8 percent lower in the
women on
the 7th day of the soup experiment than on the first
day.
Yes,
make it soup
Current
dietary recommendations say that everyone should eat at
least five portions of fruits and
vegetables
a day to reduce the risk of major illness, including
cancer and heart disease. The results of this study,
Martin says, "strongly
suggest that increasing vegetable consumption could improve
human health."
Martin says he and his colleagues designed this
and some earlier studies to examine the effects of ingesting
vitamin C through diet rather than in the form of vitamin supplements.
While vitamin C is a critical nutrient in a number of biological
processes, the human body can't produce it naturally and must
acquire it from dietary sources.
A year ago, Martin's team
did a study that found similar benefits from regular consumption
of orange juice. Blood concentrations of vitamin C rose significantly
among a group of volunteers who drank two glasses or orange
juice every day for 2 weeks. Citrus fruits are the chief source
of vitamin C in Western diets, Martin points out, but tomato-based
products are also an important source.
Martin says "hundreds of studies" have demonstrated that vitamin C is an important
nutrient for human health, "although we don't know the exact mechanisms behind
these healthy effects." Analyzing the effects of vitamin C in the bloodstream,
he says, is a stand-in for studying various functions of vitamin C in human tissues.
"Vitamin
C is one of the most amazing nutrients in the human diet," Martin says.
Among other things, it's important in the production of collagen proteins,
which
form bone and cartilage in vertebrates. It's also a cofactor in the production
of
several signal transmitters in the brain.
Brain tissue, Martin notes, contains
the highest concentrations of vitamin C in the body. In a study 2 years
ago, he and his colleagues found that increased concentrations of vitamin
C in
cells of human brain tissue improved the function of lysosomes, which are
cell parts
containing enzymes that break down and eliminate waste products. Scientists
now know that the function of lysosomes decreases as people age, Martin
points out.
While the present study examined the effects of increased vitamin C intake
in healthy young people, Martin says he's convinced that the results would
hold
in other populations, including the elderly.
Sources:
Antonio Martin Nutrition and Neurocognition Laboratory
Jean Mayer U.S. Department of Agriculture-Human Nutrition
Research Center on Aging
Tufts University 711 Washington
Street
Boston, MA 02111-1524
From
Science News, Vol.
166, No. 20, Nov. 13, 2004
Copyright (c) 2004 Science Service
