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Can Eating Garlic Prevent or Cure Common Cold and Flu?

Garlic (Allium sativum) has been used for centuries both as a medicinal and culinary herb. This pungent health promoting herb is touted to possess strong antiviral, antimicrobial, antioxidant and antibacterial properties, and it is popularly believed to be an effective remedy for the common cold and flu. As a result of the strong interest in the use of garlic as a potential cold and flu remedy, several studies have been carried out to investigate whether garlic can indeed fight and cure the common cold and flu.

Eating garlic
Eating garlic may prevent a cold but not cure an existing cold, study shows.

However, according to a Cochrane review published in 2012, many of these studies were conducted improperly, affecting outcomes. The researchers behind this Cochrane review searched the Cochrane Central Register of Controlled Trials for placebo-controlled trials that investigated the relationship between garlic and common cold prevention or treatment. Of all the studies conducted on the ability of garlic to prevent and/or cure the common cold and flu, only one met the quality criteria set by the reviewers.

The clinical trial that met the set criteria involved 146 participants, all of whom were recruited through advertisements in London daily newspapers. The participants were randomly assigned to receive either a daily garlic supplement (containing 180 mg of allicin, the main active compound in garlic) or a placebo for 90 days. All participants were asked to keep a diary in which they could record their well-being on a five-point scale during the trial period. If they came down with a cold during the trial, they were additionally asked to record the number and variety of symptoms as well as details of the recovery.

The trial reported 24 occurrences of the common cold in the group that received the allicin-containing garlic supplement, compared with 65 occurences in the control group. This suggests that garlic may indeed help prevent the common cold and flu. However, the study reported no significant differences in the number of days it took the participants to recover from a bout of the common cold (4.63 days in the garlic group versus 5.63 days in the placebo group).

Cold-Fighting Mechanisms of Garlic

Garlic has been shown to possess antiviral, antimicrobial, antioxidant and antibacterial properties, all of which may contribute to the alleged ability of garlic to prevent common cold and flu symptoms. Many of the beneficial properties of garlic have been associated with allicin, a compound that is produced when raw garlic is crushed or chopped. To reap the potential cold and flu fighting effects of allicin, it is best to let chopped or crushed garlic sit for a while before using it in your recipe. Research shows that letting crushed garlic sit for 10 to 15 minutes before cooking it helps maximize the allicin content of this wonderful herb.

In addition to allicin, garlic provides an abundance of nutrients that may help prevent the common cold and flu by boosting the body's natural disease-fighting mechanisms. These include vitamin C (a common remedy for colds), selenium and zinc.

Potential Side Effects

For most of us, eating garlic in moderation holds no serious side effects. However, depending on the amount of garlic you consume, you may experience some mild side effects such as heartburn (especially during pregnancy), increased perspiration and body odor, stomach problems (such as diarrhea), lightheadedness, and an unpleasant burning sensation in the mouth or stomach.

Before you add garlic to your cold prevention diet, you should talk to you doctor if you take medications — many drugs are known to interact with compounds present in garlic. These medications include but are not limited to anti-coagulant, antiplatelet, and anti-viral drugs. Also some contraceptive drugs may lose their power when garlic is consumed in large quantities.


1. Lissiman E, Bhasale AL, Cohen M. Garlic for the common cold. Cochrane Database of Systematic Reviews 2012, Issue 3
2. Josling, Peter (2001). Preventing the Common Cold With a Garlic Supplement: A Double-Blind, Placebo-Controlled Survey. Advances in Natural Therapy, 18(4).

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