We decided to investigate what science says about the popular remedy of eating more garlic or placing garlic cloves in rooms to protect against infections during the cold and flu season.
Various cultures, from ancient Egypt and Greece to China and India, have documented evidence of using garlic, one of the first plants that humans began to use for treating various illnesses, in medicine. Hippocrates also prescribed garlic for various illnesses. However, what does modern science say about its effectiveness?
When mixed together, alliin and allinase, found in garlic, transform into allicin, a substance with strong antimicrobial and antifungal effects. Allicin also improves the functioning of the immune system, helping the body fight various illnesses, including colds. To produce allicin, garlic needs to be sliced or otherwise crushed because alliin and allinase are found in different parts of the garlic bulb
Specialists from the American Society for Microbiology claim that allicin is effective against the majority of bacteria, fungi, and even viruses. It can also slow down the growth of some parasites.
Scientists from the University of Florida conducted an experiment in 2016, where they divided 120 healthy participants into two groups during the cold and flu season. One group was given an extract of aged garlic, while the other was given a placebo. The study lasted for 90 days, and although the number of people who got sick in both groups was not significantly different, those who took the garlic extract had an easier time with the illness and recovered faster than those who were given the placebo.
In an experiment conducted in 2001, 146 volunteers took allicin-containing supplements (or a placebo) for 12 weeks from November to February. The participants who took allicin got sick more than two times less often than those who took the placebo, and their recovery time was significantly shorter from the onset of the illness.
Scientists from several countries conducted a systematic review of existing research that confirmed the hypothesis of garlic’s preventative properties against colds by enhancing the immune response.
However, it matters in what form you consume garlic. Garlic loses its potency if exposed to the microwave for 60 seconds or 45 minutes in the oven, as it does not allow the active substances to be released. To preserve the benefits of garlic, specialists suggest leaving it sliced for 10 minutes before cooking. The effectiveness of garlic derivatives and spices in comparison to fresh garlic remains undetermined as scientists have not been able to determine the difference yet.
Despite the evidence supporting the effectiveness of garlic and its derivatives in combating colds and the flu, not all researchers agree. Australian scientists who summarized the data of previous scientific works on this topic concluded that there are certain grounds to consider garlic an effective means of preventing and treating colds, but additional, more extensive and reliable research is needed to say for sure. The same applies to the effectiveness of garlic against the flu.
The US National Institutes of Health states that currently, there is insufficient evidence to support the claim that garlic can actually prevent or alleviate the course of colds or the flu.
It is worth noting that all studies that confirmed the effectiveness of garlic for the prevention and treatment of colds involved the internal consumption of garlic or its derivatives. There are currently no studies that confirm the effectiveness of garlic when inhaled
Scientists have yet to reach a consensus on the efficacy of garlic against colds and the flu. While some specialists argue that it can shield against sickness or ease its progression, others assert that the evidence is inadequate or of poor quality. As there is some evidence to suggest its effectiveness, it may be beneficial to incorporate garlic into one’s diet during the respiratory infection season. However, a healthy stomach and intestines are necessary for this. If they are not functioning well, garlic may cause more harm than good.
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