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Clearing
the air on garlic
April 20, 2006
Suzanne Havala Hobbs
Is
someone you know on a garlic binge?
If so, they’ve likely heard some of the claims floating
around on the web and in health food stores: Garlic kills
germs, protects your heart and prevents colds.
Or these: Garlic cures acne, improves your sex life, and repels
mosquitoes (apparently in addition to vampires).
Garlic – a plant in the allium family, related to onions
and leeks – has been used since ancient times as both
a medicine and a condiment or seasoning in foods. Even if
you don’t use it for medicinal purposes, you probably
eat garlic regularly. It’s a common ingredient in soups,
dips, casseroles and other cooked dishes. The edible bulbs
or cloves (there may be a dozen in a head of garlic) have
a distinctive flavor and odor that tends to linger on the
breath.
The truly devoted pop a whole fresh clove a day in hopes of
health benefits. It’s not hard to identify them.
I’ll never forget the evening I spoke at a community-wide
heart health intervention program in Kalamazoo, Mich., and
was caught up afterwards in a throng of hundreds of participants,
several of whom nearly bowled me over with the overpowering
odor of garlic as they approached to talk diet.
Are the benefits of garlic worth the social cost? What’s
the truth about the health claims?
Here’s what we know:
In addition to vitamins and minerals, plant foods such as
fruits and vegetables contain other health-supporting components
called phytochemicals. There are likely thousands of these
substances in foods, and we don’t know a lot about many
of those that have been identified at this point.
One class of phytochemicals that there is a substantial body
of research on, however, is plant sulfur compounds. Garlic
is a rich source of sulfur compounds.
In fact, the Agency for Healthcare Research and Quality in
2000 published an evidence-based report on garlic and its
health benefits. A summary of the report can be found online
at http://www.ahrq.gov/clinic/epcsums/garlicsum.htm.
The report assessed whether garlic (fresh, cooked or supplements)
lowers blood lipid levels, blood pressure, blood sugar, or
reduces the risk of death or disability from heart disease
or cancer.
According to AHRQ:
* There wasn’t enough evidence to draw conclusions about
the potential for garlic to prevent heart attacks. Garlic
may lower blood cholesterol levels slightly in the short-term
(up to 3 months).
* The evidence did not support the claim that garlic lowers
blood pressure or blood sugar levels.
* A limited amount of research from case-control studies suggested
that eating garlic lowers the risk of laryngeal, stomach,
colorectal, and endometrial cancer as well as colorectal polyps.
However, single case-control studies suggested that garlic
did not protect against breast or prostate cancer.
No word on acne, sex or mosquitoes – an evidence base
built on sound science doesn’t exist yet.
The AHRQ report did document some adverse effects of garlic,
though. Smelly breath and body odor topped the list. Other
potential side effects included gas, abdominal pain and dermatitis.
Another limitation noted in the AHRQ report: Wide variability
in the types of garlic preparations used by study subjects.
Studies reviewed did not always distinguish whether subjects
used raw or cooked garlic or did not give the name or specifications
of garlic supplements.
The bottom line?
Garlic may confer health benefits, but many questions remain,
complicated by a lack of information about the various forms
in which garlic was used in studies. If you can eat it without
suffering side effects, though, there doesn’t appear
to be any reason not to enjoy it.
Unless you eat enough to clear a room.
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