How Garlic Fights Colds and the Flu

Garlic has been used for centuries as both food and medicine.

In fact, eating garlic may provide a wide variety of health benefits (1Trusted Source).
This includes reduced heart disease risk, improved cognitive health, enhanced immune function, and decreased risk of certain types of cancer (2Trusted Source, 3Trusted Source, 4Trusted Source, 5Trusted Source).

This article explains how garlic is particularly protective against the common cold and the flu.

Garlic can boost immune function

Garlic contains compounds that help the immune system fight germs (4Trusted Source, 6Trusted Source, 7Trusted Source).
Whole garlic contains a compound called alliin. When garlic is crushed or chewed, this compound turns into allicin (with a c), the main active ingredient in garlic (8Trusted Source, 9Trusted Source).

Allicin contains sulfur, which gives garlic its distinctive smell and taste (8Trusted Source, 10Trusted Source).
Can garlic help prevent colds and the flu?

Garlic has shown promise as a treatment for preventing colds and the flu.
Studies have shown that garlic may reduce the risk of becoming sick in the first place, as well as how long you stay sick. It may also reduce the severity of symptoms (7Trusted Source, 11Trusted Source, 12Trusted Source).

If you often get sick with a cold or flu, eating garlic may help reduce your symptoms or prevent your illness entirely.
However, a review of the evidence found that many of the studies investigating the effects of garlic on the common cold were of poor quality (11Trusted Source).
It’s also unknown if you need to take garlic constantly, or if it also works as a short-term treatment when you start getting sick.

How to maximize the benefits of garlic

The way garlic is processed or prepared can change its health benefits.
Ensure whole garlic is crushed, chewed, or sliced before it’s eaten. Let crushed garlic stand for 10 minutes before you cook it.

Garlic supplements

Another easy way to increase your garlic intake is by taking a supplement.
However, be cautious, as there are no regulated standards for garlic supplements.
That means the allicin content and quality can vary, and so can the potential health benefits.

Powdered garlic

Powdered garlic is made from fresh garlic that has been sliced and dried. It doesn’t contain allicin, but is said to have allicin potential.
Powdered garlic is processed at low temperatures and then put inside capsules to protect it from stomach acid.
This helps the enzyme alliinase survive the harsh environment of the stomach so that it can convert alliin to the beneficial allicin in the intestine.
Unfortunately, it’s unclear how much allicin can be derived from powdered garlic supplements. This varies greatly depending on the brand and preparation (15Trusted Source).

Aged garlic extract

When raw garlic has been sliced and stored in 15–۲۰% ethanol for over 1.5 years, it becomes aged garlic extract.
This type of supplement doesn’t contain allicin, but it does retain the medical properties of garlic.

Garlic oil

Common types of garlic supplements include powdered garlic, aged garlic extract, and garlic oil. Aged garlic extract may offer the greatest health benefits.
How much garlic should you eat per day?

There is no established effective dosage of raw garlic or garlic supplements. Since high intakes of garlic supplements can be toxic, don’t exceed the dosage recommendations.