Garlic For Colds and the Flu – Does It Help?

Garlic (Allium sativum) has been valued across many cultures for both its delicious flavor and potential health benefits (1).

You may know about garlic’s connection to heart health, but it’s also gaining attention for its ability to strengthen your immune system.

Research suggests it might help lower your risk of catching colds and flu, reduce their severity, and shorten how long they last (2).

Let’s explore the active compounds in garlic and how they might help protect you from seasonal illnesses.

Chemical Composition and Active Compounds

The health benefits you get from garlic primarily come from its sulfur-containing compounds.

These include allicin, diallyl disulfide, and diallyl trisulfide (3, 4).

These powerful compounds form when you crush or chop garlic, which activates an enzyme called alliinase (5).

While allicin often gets most of the attention, other compounds like S-allylcysteine (found in aged garlic extract) also play important roles in supporting your immune system (6).

Immune System Support

Garlic can help strengthen your body’s natural defenses in several ways.

Immunomodulatory Properties

Research shows that garlic can enhance or modify your immune responses (7, 8).

It can boost the function of your white blood cells, including lymphocytes, natural killer cells, and macrophages (9).

The sulfur compounds in garlic can also help reduce inflammation and oxidative stress, which may improve how effectively your immune system responds to threats (10).

Aged garlic extract contains high levels of the stable compound S-allylcysteine, which research shows has significant immune-supporting properties (11).

Helps Prevent Colds and Flu

You may catch fewer colds when you regularly consume garlic, thanks to its immune-supporting and antimicrobial effects.

Several reviews and clinical trials suggest that routine use of garlic can reduce how often you get the common cold (12, 13).

One interesting study focused on travelers exposed to airborne illness. It found that an intranasal spray containing cellulose plus powdered garlic significantly reduced reported illnesses (14).

Ability to Combat Colds and Flu

Garlic doesn’t just help prevent illness; it may also help you recover faster if you do get sick.

Prevention

One frequently cited clinical trial found that people taking a daily garlic supplement with allicin had significantly fewer colds compared to those taking a placebo (15).

When they did catch a cold, they recovered more quickly than the placebo group.

A respected Cochrane review of this trial concluded that garlic may help with cold prevention, though they noted the need for more high-quality studies (16, 17).

Decrease in Severity and Duration of Symptoms

If you do catch a cold or flu, aged garlic extract might help you feel better faster.

Studies show it can reduce the severity of your symptoms and shorten the number of days you’re sick (18, 11).

In these studies, people taking aged garlic extract experienced fewer total days of illness and recovered more quickly than those taking a placebo.

Prevention in Children

Garlic may help protect your children from getting sick too.

In a double-blind, placebo-controlled study, children given long-acting garlic tablets had far fewer respiratory infections compared to those given a placebo (19).

Importantly, the children didn’t experience any major side effects from the garlic tablets.

Systematic Reviews on Therapy Effects

When scientists review all the research on garlic for respiratory infections, they typically find positive results overall.

However, these reviews frequently note that larger, higher-quality clinical trials would help confirm these benefits (20, 21).

Antimicrobial and Antiviral Properties

How does garlic help you fight off infections? Its extensive antimicrobial, antiviral, and antifungal properties play a key role.

These properties help explain why garlic may reduce your cold and flu symptoms (5).

Compounds like allicin may help block viruses from entering your cells and stop them from multiplying.

These compounds also seem to affect several different immune pathways in your body (22).

Anti-Inflammatory and Antioxidant Effects

Colds and flu often cause inflammation in your airways, which contributes to symptoms like congestion and sore throat.

Garlic’s anti-inflammatory effects may help reduce this inflammation and ease your symptoms (23).

The antioxidants in garlic also protect your cells from damage caused by free radicals.

This protection may contribute to a stronger, more resilient immune system (24).

Utilizing Garlic as a Complementary Therapy

Many people use garlic or garlic supplements to help prevent colds and flu or to ease symptoms when they do get sick (25, 14).

For even greater benefits, you might try combining garlic with other immune-supporting herbs or spices.

Research suggests this combination approach may enhance garlic’s antimicrobial effects (26).

Benefits of Aged Garlic Extract

Aged garlic extract is made by aging fresh garlic in water-based solutions for up to 20 months.

This process creates stable sulfur compounds like S-allylcysteine (27).

Multiple studies show that aged garlic extract can boost the activity of certain immune cells, including natural killer cells.

This may help you experience fewer colds and flu, with milder symptoms when you do get sick (11).

Safety and Side Effects

Before adding garlic supplements to your routine, it’s important to understand potential side effects.

General Safety Profile

For most people, garlic is safe when consumed in normal food amounts.

Side effects are usually mild and may include garlic odor or slight stomach upset (28, 29).

However, be careful not to apply raw garlic directly to your skin, as this can cause burns (30).

Possible Side Effects and Interactions

Very high doses of garlic can potentially cause toxicity in certain cells and organs (31).

If you have a bleeding disorder or are scheduled for surgery, be aware that high amounts of garlic may increase your bleeding risk (29).

Garlic can also interact with certain prescription medications.

Always check with your healthcare provider before taking large doses of garlic supplements (32).

Balanced View and Research Gaps

While the evidence for garlic’s benefits looks promising, there are some limitations to consider.

Limitations in Current Evidence

Studies consistently show that garlic can help reduce how often you get colds and how severe they are when you do get sick.

However, most experts point out that we need more large, high-quality clinical trials to be completely certain (16, 17).

Different studies use different garlic preparations and research methods, which can make it hard to compare results directly.

Importance of Standardization

You can consume garlic in many forms, including fresh, powdered, oil-based, or as aged extracts.

The concentration of active compounds varies between these forms, which can affect the results you experience (6).

Scientists are still working to determine which garlic preparation and dosage is best for preventing and treating colds and flu.

Conclusion

Research strongly suggests that garlic, especially allicin-containing products and aged garlic extract, can boost your immune function.

This may help you catch fewer colds and flu, with milder symptoms and faster recovery when you do get sick (11, 15).

Garlic’s antibacterial, antiviral, and anti-inflammatory properties can support your respiratory health in multiple ways (8).

For most people, adding garlic to your diet or taking garlic supplements is safe and may provide valuable immune support during cold and flu season.

If you’re considering high-dose garlic supplements, especially if you have bleeding disorders or upcoming surgery, check with your healthcare provider first (29).

Garlic has stood the test of time as a natural way to support immune health and reduce the burden of colds and flu, backed by both historical use and growing scientific evidence.