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Fight Colds and Flu With Garlic

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Garlic belongs in the onion plant family and it is the most potent of the medicinal members of this family. Its use date back to the ancients who used it as a sort of “cure-all”. Although garlic may give you bad breath, it is quite effective for fighting infections, boosting the immune system and mopping up harmful free radicals. These are the same medicinal properties that make garlic so essential for fighting colds and flu. But how does garlic achieve all these? How does garlic compare to recommended flu treatments? And how should garlic be used for maximal effectiveness? Read on to find out.

Health Benefits of Garlic

Garlic or Allium sativum is a plant closely related to the onion and also shallot and leek. Garlic has been used both as a food and medicinal remedy for over 7,000 years.

In ancient Greek, Roman, Egyptian and Chinese societies, garlic was used to treat a number of conditions including respiratory and digestive problems. It is also used as a tonic and restorative.

In modern societies, garlic is used in traditional medicine to help prevent high cholesterol, atherosclerosis, high blood pressure, and heart diseases. In addition, garlic can lower blood sugar levels, prevent blood clotting, act as an expectorant for relieving cough and protect against the common cold.

Garlic is also effective for treating bacterial and fungal infections especially those affecting the respiratory and gastrointestinal tracts.

Key Nutrients in Garlic
  • Dietary fiber
  • Proteins
  • B vitamins except for vitamin B12
  • Vitamin C
  • Calcium
  • Magnesium
  • Potassium
  • Selenium
  • Iron
  • Manganese
  • Zinc

Besides these nutrients, garlic is also known for its bioactive sulfur-rich compounds. The most important of these compounds are allicin and alliin.

These sulfur compounds are chiefly responsible for the antibacterial, antiviral, antiprotozoal and antifungal properties of garlic.

A related compound known as allixin also has antimicrobial properties but it is a non-sulfur compound. Allixin also has antitumor and antioxidant properties.

These bioactive compounds are released after raw garlic bulbs are crushed.

The sulfur compounds are also responsible for the taste and smell of crushed garlic. Specifically, the “hot” sensation felt after eating raw garlic is due to allicin. Unfortunately, the allicin content of garlic is significantly reduced after garlic is cooked.

How Garlic Can Help Fight Colds and Flu

The Best Way to Use Garlic for Colds and Flu

Raw garlic is the best form of the herb because allicin and the other medicinal compounds in garlic are released soon after garlic cloves are crushed. The processes of crushing, chopping and chewing open up the cells of garlic to release a number of compounds.

Most of these compounds are unstable and, therefore, react to form new compounds that are responsible for the medicinal properties of garlic.

Of the plants in the onion (onion, garlic, leek, shallot, etc.) family, garlic produces the highest amounts of these new compounds. It is, therefore, the most medicinal member of the family.

Garlic is best eaten within the first hour after crushing it. Researchers from South Carolina Medical University found out that the highest concentrations of these antimicrobial compounds were produced by leaving peeled garlic uncovered for 15 minutes.

Ideally, it takes that amount of time for the bioactive compounds to get synthesized after garlic cloves are crushed.

Because heat destroys most of these compounds, cooked garlic is not as medicinal as fresh, raw garlic.

Where raw garlic cannot be obtained, dietary supplements containing garlic extract may still be effective. However, you should ensure that the garlic supplement you choose is standardized by its allicin content.

The Antiviral Effect of Garlic

Although very few studies have been done to investigate the benefits of garlic for preventing and treating colds and flu, those studies have been positive. In fact, one found that garlic was better than Tamiflu, a prescription antiviral drug regularly prescribed for the flu.

In addition, garlic seems to perform better than even flu shots. Even though they are officially promoted, there is scant scientific evidence to suggest that flu vaccines are effective against the flu.

The efficacies of drugs like Tamiflu are also in doubt especially considering the fact that the results of most studies investigating the efficacy of Tamiflu are still withheld by the parent company.

Garlic, on the other hand, is a natural remedy for fighting infections especially those affecting the respiratory and gastrointestinal tracts. Since colds and flu are driven by viral infections and most of their symptoms involve the respiratory and gastrointestinal system, garlic should be effective protection during the flu season.

Health experts recommend that raw garlic should be used to prevent and treat colds and flu. While raw garlic may give you bad breath, raw is the most healthful form of the garlic.

In fact, the compounds responsible for the pungent taste and flavor of garlic are also bioactive ones.

The most potent phytochemical in garlic is allicin. The broad antimicrobial property of allicin makes it effective against a number of bacterial, fungal and viral infections.

Studies confirm that garlic is effective against drug-resistant microbes and that the antiviral effect of the herb is active against at least some of the hundreds of viruses responsible for common cold and influenza.

Besides its antiviral properties, the antibacterial effect of garlic is also important in the treatment of colds and flu. Bacterial infections usually appear during cold and flu episodes because the immune system is already weak.

Therefore, garlic can also help stop the opportunistic bacterial infections that may appear along with colds and flu.

Antioxidant Properties of Garlic

The antimicrobial properties of garlic are not the only important medicinal property of the plant. Garlic is also a potent antioxidant and this can help protect against colds and flu as well as improve their symptoms.

First, garlic is known to increase the production of hydrogen sulfide once ingested. A recent study published in the Proceedings of the National Academy of Sciences demonstrated that the addition of small amounts of garlic extract increased the production of hydrogen sulfide in human red blood cells.

This result means that eating garlic can raise your blood level of hydrogen sulfide.

Hydrogen sulfide is a potent antioxidant that can help remove harmful free radicals as well as destroy microbial cells. In fact, the authors of the study credited the ability to increase hydrogen sulfide production as responsible for the anti-tumor properties of garlic.

Researchers from Albert Einstein College of Medicine also found that the hydrogen sulfide released by garlic was partly responsible for the cardioprotective roles of garlic.

According to experts, the amount of garlic you need to consume daily to effectively raise the production of hydrogen sulfide is 2 medium-sized cloves. However, because cooking lowers the potency of garlic, you may need to eat 4 -5 cloves of garlic when they are used to prepare your dishes.

However, raising the blood level of hydrogen sulfide is not the only mechanism by which garlic serves as an antioxidant.

Garlic is rich in vitamin C and selenium, both of which are potent antioxidants too.

Vitamin C and selenium are used to make antioxidant compounds and enzymes in the body. They can help slow down the replication of cold and flu viruses by ensuring that these pathogens do not have the ideal environment to thrive.

The Immunomodulatory Properties of Garlic

A healthy immune system is really the best defense against cold and influenza viruses. Boosting the immune system against prevalent influenza viruses is what flu vaccines are meant for but rarely achieve.

Natural remedies like garlic, however, provide a general immune boost that makes them effective against any cold and flu virus.

Some of the best evidence to support that the immune-boosting power of garlic was published in 2012. First, researchers from the University of Florida reported that eating garlic boosted the level of T cells in the blood.

T cells are lymphocytes that are important to the mechanisms by which the immune system stops infections. By raising blood levels of T cells, garlic ensures that the immune system is well prepared to meet and disarm the viruses responsible for the common cold and the flu.

In addition, another 2012 study (discussed below) found that garlic enhanced the activities of NK cells.

NK or Natural Killer cells are a central part of the “attack” arm of the immune system. These cells can definitely help stop cold and flu viruses.

As more studies are done to investigate the benefits of garlic consumption on colds and flu, scientists are bound to find more ways by which garlic boosts the immune system. It is very likely that the immune-boosting properties of garlic are even more important to the prevention and treatment of cold and flu than its antioxidant and antimicrobial properties.

Studies on Garlic, Colds, and Flu

Garlic and Common Cold

The most quoted and one of the very few studies to investigate the benefits of garlic in the treatment of common cold was published in the journal, Advances in Therapy, in 2001.

For the double-blind study, the researchers recruited 146 participants and randomized them to receive either placebo or one capsule per day of Allimax, a garlic supplement standardized by its allicin content, over a period of 12 weeks during the flu season.

The results showed that the

  • garlic group suffered from fewer colds than the placebo group (24 vs. 65)
  • garlic group had fewer days of sickness than the placebo group (111 days vs. 366 days)
  • garlic group experienced a shorter duration of sickness than the placebo group (1.52 days vs. 5.01 days)

The researchers, therefore, concluded that garlic reduced the risk of coming down with a cold and sped up recovery for those who did get sick. Therefore, allicin-containing garlic extract supplements are effective for preventing and/or treating the common cold.

The only adverse effects reported were the pungent odor of garlic and mild rashes.

Cochrane Review

A 2012 review conducted by the Cochrane Collaboration to investigate the efficacy of garlic for common cold also confirmed that the 2001 study quoted above was well-designed and demonstrated the efficacy of garlic supplementation for the prevention of common cold.

In a search of scientific literature, the reviewers could only find 6 studies done on the subject and only one (the above study) was rigorous enough to meet their inclusion criteria.

While the reviewers concluded that only limited conclusions can be derived from only one study, they acknowledged that its methodology and results supported the authors’ conclusions.

However, the Cochrane reviewers called for more studies in order to reach a definite conclusion.

Garlic and Echinacea for Colds and Flu

In an editorial published in the Journal of the National Medical Association in 2000, a doctor from Florida argued for the evaluation of the combination of garlic and echinacea in the treatment of common cold and flu.

In his extensive write-up, the doctor noted that efficacies of both herbs have been repeatedly confirmed by consumers who took them during cold-flu seasons.

In addition, the author claimed available studies into the medicinal properties of these herbs indicated that they may be useful in the prevention and treatment of common cold and influenza infections.

Therefore, he argued that researchers should concentrate more on determining whether the herbs can indeed help during the cold season rather than wasting too much effort on costly antiviral medications and unproven flu shots.

The author mentioned the roles of garlic and echinacea as immune modulators as important to their benefit for fighting the viruses responsible for cold and influenza.

He also mentioned a study conducted in Japan that confirmed that garlic prevented influenza infections in mice. That study also showed that the mice who were given both garlic and flu vaccines produced more antibodies than those given only flu vaccines.

This editorial confirmed that the benefits of garlic for colds and flu are not lost in the medical community. What is lacking is the will (and the financial incentive) to conduct independent clinical trials to confirm what millions of users who take garlic every cold-flu season already know.

The Immune-boosting Power of Garlic

A 2012 study published in the journal, Clinical Nutrition, investigated the effects of garlic supplementation on the proliferation and activities of immune cells.

For the study, the researchers recruited 120 healthy subjects. Half of them were given 2.56 g/day of an aged garlic extract supplement while the other half received a placebo.

The results showed that after 45 days, the participants taking the garlic supplement had higher levels of NK cells as well as T cells.

After 90 days, the results showed that although the incidence of colds and flu were the same with both groups (likely because aged and not fresh, allicin-rich garlic supplement was used), the severity and duration of cold and flu symptoms were significantly lower in the garlic supplement group than the placebo group.

The researchers, therefore, concluded that garlic reduced severity and sped up recovery from colds and flu because it boosted the immune system.





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