Garlic is a popular culinary herb, related to onions and lilies,
that is steeped in a rich mythology suggesting it repels werewolves
and vampires. Replace these ancient devils with modern scourges
such as raised cholesterol and hardening of the arteries and
research supports its positive effect on health. The main
beneficial substance derived from garlic is allicin. Allicin is
present in whole garlic cloves as an odourless precursor called
alliin. When garlic is crushed or sliced, alliin comes into contact
with a garlic enzyme, alliinase, which breaks it down into the
allicin (diallyl thiosulphinate) that gives crushed garlic its
characteristic smell. Sulphur compounds formed by the degradation
of allicin also have a beneficial antioxidant action.
Lowers cholesterol: Allicin reduces cholesterol
production in the liver, prevents cells from taking up cholesterol
and hastens excretion of fatty acids to discourage hardening and
furring-up of the arteries. Garlic can lower levels of harmful
LDLcholesterol by up to 12% and triglycerides - another type of
circulating fat - by 8% to 27% 1-2. Antioxidants derived
from garlic also reduce oxidation of circulating fats which may
have a beneficial, protective effect in people with cardiovascular
disease3.
Inhibits arterial plaques: Researchers
following 152 patients for over 4 years found that garlic tablets
could reverse hardening and furring-up of the arteries
(atherosclerosis). In those not taking garlic tablets, arterial
thickenings (plaque) built up by 15.6% over the four years, while
in those taking garlic, plaque volume decreased by 2.6% - a
combined difference of 18.2%4. Another study found that
garlic tablets can increase the elasticity of the aorta so the
heart has to work less hard to pump blood out into the
body5.
Lowers blood pressure: Taking garlic extracts
can reduce blood pressure by around 8%, making it beneficial for
people with mild hypertension6.
Improves circulation: Garlic can reduce
abnormal blood clotting and improve blood flow to the skin and nail
folds by almost 50%7, making it useful for people with
symptoms due to poor peripheral circulation such as Raynaud’s
disease, chilblains and calf pain on walking.
Lowers homocysteine: Elevated blood levels of
the amino acid, homocysteine, are linked with hardening and
furring-up of the arteries. Garlic extracts have recently been
shown to help lower homocysteine levels - a beneficial effect that
is under further investigation.
Something for the winter months: Garlic has
antioxidant, antiseptic, antibacterial and antiviral properties. It
is used to treat intestinal, respiratory and skin infections by
stimulating an immune response known as t-cell proliferation.
People taking garlic extracts have significantly fewer colds and,
if they do succumb, a significantly shorter duration of symptoms
than those taking an inactive placebo8.
1. Silagy C, Neil AW 1994. Garlic as a lipid
lowering agent - a meta-analysis. J R Coll Phys London 28:39-45
(1)
2.Mader FH 1990. Treatment of hyperlipidemia with garlic
powder tablets. Arzneim-Forsch Drug Res 40:1111-1116 (2)
3. Ou CC et al. 2003. Protective action on human LDL
against oxidation and glycation by four organosulfur compounds
derived from garlic. Lipids. 38;3:219-24. (3)
4. Koscielny J et al. 1999 The antiatherosclerotic
effect of Allium sativum. Atherosclerosis 144:237-249 (4)
5. Breithaupt-Grogler K et al. 1997 Protective effect of
chronic garlic intake on elastic properties of aorta in the
elderly. Circulation 96:2649-2655 (5)
6. Silagy C, Neil AW. 1994. A meta-analysis of the
effect of garlic on blood pressure. The Journal of Hypertension,
12:463-468 (6)
7. Kiesewetter H et al. 1991 Effect of garlic on
thrombocyte aggregation, microcirculation and other risk factors.
Int J Clin Pharm Tox Therapy 29;4:151-155 (7)
8. Josling P 2001. Preventing the common cold with a
garlic supplement: a double-blind, placebo-controlled survey. Adv
Ther 18;4:189-93 (8)
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