What Is Allicin?

Allicin is a compound that may help ease inflammation and block free radicals, unstable molecules that harm cells and tissues in your body. The compound is one of garlic's primary active components and gives it its distinct taste and scent.

The amino acid alliin is a chemical found in fresh garlic and is a precursor of allicin. An enzyme called alliinase is activated when the clove is chopped or crushed. This enzyme converts alliin into allicin.

Here's what to know about allicin's possible health benefits, risks, and how to use it.

Uses of Allicin

Many studies have shown that the allicin in garlic may support health in various ways. Here's a look at some of the more compelling evidence.

Cholesterol

A review of 39 randomized controlled trials (a study that randomly assigns participants to experimental and control groups) found that regular use of compounds in garlic lowered people's cholesterol levels by about 8%.

In general, adults in the study with slightly elevated cholesterol levels—above 200 milligrams per deciliter (mg/dL)—who took garlic for at least two months had lower:

• Low-density lipoprotein (LDL), considered "bad cholesterol"
• Total cholesterol

A 2016 review of studies also supports these findings. The results of eight of nine reviews found a marked decrease in total cholesterol.

Blood Pressure

Research suggests that allicin may help lower blood pressure and keep it within a healthy range. 

In adults with high blood pressure who took garlic supplements, the mean systolic blood pressure (the top number in a blood pressure reading) was around 8 points lower than those who took a placebo (sugar pill). Their diastolic blood pressure (the bottom number) was about 5 points lower.

Cancer

In 1990, the National Cancer Institute (NCI) praised garlic for its ability to guard against cancer. Since then, multiple preclinical studies have shown that allicin and other active garlic compounds may shield against some cancers and keep cancer cells from spreading.

Research has explored its role against cancers of the:

• Breast
• Colon
• Liver
• Head and neck
• Ovaries
• Pancreas
• Prostate
• Skin

It's important to note that most of these studies were done on animal models or cells in a test tube. Robust human trials are needed to learn more about allicin's effects on cancer.

The NCI does not recommend taking garlic supplements to prevent cancer.

Infection

Garlic is a natural antibiotic whose use has been documented since the 1300s. Allicin is the compound responsible for garlic's ability to fight illness. It's considered broad-spectrum, meaning it's able to target the two main types of bacteria that cause disease.

Allicin also seems to enhance the effect of other antibiotics. Because of this, it may help combat antibiotic resistance, which happens when, over time, bacteria do not respond to medicines meant to kill them.

Other Uses

In addition to the potential health benefits listed above, some people use allicin to help muscle recovery after a workout.

What Are the Side Effects of Allicin?

Your healthcare provider may recommend you take allicin to help lower blood pressure, blood sugar, or cholesterol or for other conditions. Allicin has some side effects to be aware of, and these may be common or severe.

Common Side Effects

Allicin causes a garlic odor or breath in about 1 in 3 people who use it.

It may also cause digestive issues, especially in high doses, such as:

• Belching
• Gas
• Nausea
• Diarrhea
• Heartburn

These side effects may be more common with raw garlic than with supplements. Taking allicin with food may help limit or prevent these problems.

Severe Side Effects

Skin blisters and burns have been reported with raw garlic topical application (on the skin). High doses may cause liver damage.

Precautions

It is not known whether it is safe to take the compound for:

• Pregnant women
• Nursing parents, although limited data suggests that supplementing for a few days is unlikely to cause harm other than potentially mild digestive issues in the nursing infant
• Children, but use is cautioned against in babies under 10 months old

Garlic may cause allergies and shouldn't be taken if you are allergic to plants in the lily family, including:

• Hyacinth
• Tulip
• Onion
• Leeks
• Chives

If you are due to have surgery or another procedure, your healthcare provider may recommend that you avoid garlic and products with its compounds for seven to 10 days beforehand. This is because garlic can increase the risk of bleeding.

Dosage: How Much Allicin Should I Take?

There is no standard dose for allicin. The dose can vary based on your health needs and the specific product. In general, it's best to follow the instructions on the label.

Standard doses used in blood pressure studies were 600 to 900 milligrams (mg) daily of garlic powder for up to 24 weeks; 600 mg of garlic powder contains approximately 7.8 mg of allicin.

Higher daily doses are often divided into multiple doses taken throughout the day. Breaking up doses may also help limit some of the digestive side effects.

Be sure to talk with your healthcare provider about the correct dose for you.

What Happens If I Take Too Much Allicin?

So far, studies show little evidence of toxicity from allicin. One report suggested that septicemia (a serious blood infection), bradycardia (slow heart rate), or loss of consciousness could occur if high doses of allicin are taken for long periods.

More research is needed to determine if allicin could be toxic to adults at high doses.

If you are concerned about these or any other potential side effects, always discuss the use of allicin with your healthcare provider.

Interactions

Allicin and other garlic compounds help keep blood clots from forming. This may raise the risk of bleeding.

Be sure to talk with your healthcare provider if you also take a blood thinner such as Jantoven (warfarin), or other herbal and OTC aids that can thin your blood, such as:

• Aspirin
• Ginkgo biloba
• Vitamin E

Avoid high doses (more than 4 grams of fresh garlic or 3 mg of allicin) if you take warfarin or other blood thinners.

Allicin also interacts with a class of medicines called protease inhibitors used in human immunodeficiency virus (HIV) treatment.

If you have blood pressure or blood sugar issues and take medicines to manage these, be sure to talk with your healthcare provider before you try allicin. Using allicin at the same time may cause your blood pressure or blood sugar to drop too low, though there is not much evidence that these interactions cause harm.

It is essential to carefully read a supplement's ingredient list and nutrition facts panel to know which ingredients and how much of each ingredient is included. Please review this supplement label with your healthcare provider to discuss potential interactions with foods, other supplements, and medications.

How to Store Allicin

Always store allicin products as directed on the package—typically in a cool, dry place and away from children and pets.

Similar Supplements

Several supplements have similar activities as allicin. For example, some people take omega-3 fatty acids to lower cholesterol.

Other supplements that may help control blood pressure are:

• Potassium
• Magnesium
• L-arginine
• Vitamin C
• Cocoa flavonoids
• Beetroot juice
• Coenzyme Q10 (CoQ10)
• Celery
• Ginseng
• Black cumin

Supplements that may lower blood sugar include:

• Ginger
• Ashwagandha
• Aloe
• Curcumin

Many other supplements have been studied to prevent cancer. Some examples are:

• Curcumin
• Quercetin
• Resveratrol
• Beta carotenoids
• Green tea
• Vanillin

Popular supplements that may be taken to prevent or treat colds include:

• Echinacea
• Vitamin C
• Elderberry
• Zinc
  

Sources of Allicin & What to Look For

There are different methods (food and supplements) through which to get allicin. Generally getting allicin through its food source (chopped garlic) may be considered to be most effective. 

Food Sources of Allicin

Allicin is found in raw garlic, one of the most commonly used foods in cooking. And it's volatile (unstable and quickly changes into other chemicals).

A garlic clove has about 5 to 18 mg of allicin. Pure allicin only remains stable in freshly crushed or cut garlic for a short time. But letting garlic sit for 10 minutes after crushing or cutting it may help boost allicin levels. Try not to heat it above 140 degrees F; temperatures above this may degrade the amount of allicin.

Allicin Supplements

Allicin is found in garlic powder supplements, which can be formulated as:

• Enteric-coated tablets
• Non-enteric tablets
• Capsules

Enteric-coated products are designed to bypass the stomach and, in theory, yield a higher amount of allicin. This is because the enzyme that produces allicin, alliinase, is thought to be inactive in the stomach's acidic environment.

The FDA does not regulate supplements, so their quality and potency can vary. Amounts of allicin released in the body are often lower than the product labels claim.

Be sure the product has been certified by one or more of these agencies:

• ConsumerLab
• USP (U.S. Pharmacopeia)
• NSF International

Summary

Allicin is one of the main active compounds derived from garlic. It may help prevent certain cancers and may help lower blood sugar, cholesterol, and blood pressure. It may help your muscles recover after a workout and protect against infections.

Allicin supplements have few risks. It might cause some stomach upset and increase the risk of bleeding. Its safety isn't known for children or pregnant or breastfeeding women.

If you're interested in allicin supplements, talk with your healthcare provider or pharmacist about whether they're safe and beneficial.