Is Garlic So Powerful That Even One Clove Can Change Gene Expression Related to Immunity?!
Garlic is researched in various fields because it is believed to have many health benefits, from lowering high blood pressure to strengthening immunity. In this article, we will focus on garlic and cancer research. We will also examine why there are so few clinical trials involving humans.
This article is not intended to incite excessive expectations with inaccurate information such as "garlic has cancer-preventing effects" or "garlic lowers cancer risk."
While laboratory studies have shown that allium compounds in garlic have anti-cancer properties, there is no evidence from human studies that garlic lowers the risk of cancer.
More research is needed to understand how the role of garlic in cancer risk varies depending on quantity, absorption, cooking methods, and individual differences, and the data is limited for drawing conclusions about garlic and reduced cancer risk.
Laboratory Research
Most research on garlic and cancer focuses on the allium compounds in garlic. Among them, a substance called allicin is the most studied, which is produced from enzymes released when garlic tissue is damaged or crushed.
In cell and animal experiments, it has been shown that allium compounds in garlic may reduce the development of certain types of cancer or play a role in cancer prevention.
These effects are thought to be brought about by influencing gene expression, such as turning on tumor suppressor genes.
Human Studies
There are not many clinical trials involving humans related to garlic, but
I will introduce one paper here.
In a 2015 clinical trial conducted to investigate the effects of garlic,
17 people were divided into a group that ate a meal using raw garlic (5g) and a placebo group that ate a meal without raw garlic, and the subjects' blood was analyzed after one meal.
Regardless of whether health benefits have been proven or not, 5g of raw garlic is about one clove or slightly less, so I personally feel it is a high point that it was studied in an amount that can realistically be incorporated into daily eating habits.
As a result, in the group that ate the meal using raw garlic, it was suggested that 3 hours after raw garlic intake, 7 genes related to the self-destruction of abnormal cells and the regulation of immune function were activated.
The ones written as H1F1A and JUN are the genes whose gene expression was found to be activated. Statistically, P<0.01 means that the probability of not getting similar results if the same experiment is conducted again is less than 1%. With very high reliability, it seems that these gene expressions are activated by garlic intake at almost 100%.
"Activation of genes that destroy abnormal cells and regulate immune function"
It sounds good, doesn't it? But you might wonder, so what?
I wondered if there were any clinical outcomes, that is, changes we can notice such as health, function, and quality of life related to garlic intake, so I searched for papers on garlic focusing on clinical outcomes, and there were several.
For example,
① "Garlic, Helicobacter pylori, and gastric cancer risk" Systematic review and meta-analysis investigating
② "Garlic intake and colorectal cancer risk" Meta-analysis investigating
To summarize the results of these studies, they showed a significant inverse correlation between garlic intake and gastric cancer risk, and also indicated the possibility of reducing the risk for colorectal cancer.
However, these results were mainly derived based on case-control studies. Case-control studies are a method of examining the association between factors and diseases by looking back in time to compare whether or not specific factors were exposed.
Case-control studies simply explained, it's like asking people who have developed gastric cancer and those who haven't, "Did you eat garlic often?" or "Did you eat dishes using garlic regularly?" and having them recall the past, so this type of study is not considered a strong type of evidence.
Considering the limitations of case-control studies, the evidence from these studies is not sufficient to draw clear conclusions about the association between garlic and Helicobacter pylori infection or the reduction of colorectal cancer risk.
While these research results should be interpreted with caution, even in case studies, a larger number of cases increases the precision obtained from statistical analysis and enhances scientific validity.
What kind of research allows us to find a stronger type of evidence?
If a large-scale prospective cohort study can be conducted, it is expected to contribute to elucidating the fundamental preventive effects of garlic against cancer.This is a method where, instead of relying on the subjects' memories as in the research methods introduced above, we divide people into groups of those who eat garlic and those who do not, start observing them now, and track whether they develop cancer after X years.
However, if we consider why this is difficult in cancer research,
for example, in the case of osteoporosis, bone density decreases with age, especially after menopause, so if you gather 100 women over the age of 50, you can predict that bone density will decrease or has already decreased in most of those 100 women. Therefore, in terms of "gathering people" to investigate the association between bone density and something, you can recruit subjects for the study with a high probability.
On the other hand, once you have gathered 100 women over the age of 50, it is difficult to predict how many of these 100 women will develop cancer at the time you are planning the study. Considering how many people you need to gather to obtain 100 cases, you can understand that you need to gather far more cases than you would for 100 cases of osteoporosis.
Furthermore, it is easy to imagine that it becomes even more difficult if you limit it to a specific cancer, such as wanting to investigate the association with a certain type of cancer.
From this perspective as well, it costs a tremendous amount to gather cases and track them prospectively to investigate the reduction in risk between garlic and cancer. Perhaps this is why there are currently few large-scale cohort studies, and there is more research at the animal and cellular levels.
A quick tip for when you use garlic!
After chopping or crushing garlic, let it sit for about 10 minutes before cooking.
By doing this, you can ensure enough time for the enzyme alliinase to produce allicin, which is the precursor to active compounds!
In conclusion
At present, most research on the effects of garlic in humans consists of case studies, and while the level of evidence cannot be said to be high,since garlic is an ingredient we already use on a daily basis, I personally believe it is well worth taking an interest in the health benefits of garlic and actively incorporating it into your daily life.
Even if it has not been proven what kind of clinical outcomes the activation of gene expression related to immune function and foreign body destruction leads to,isn't it "amazing garlic power" that just one clove of garlic can activate these gene expressions?
Since these days we need a mask whenever we go out, I thought I would
increase the opportunities to eat garlic raw. Please be careful not to eat too much, as it is quite strong when raw.
I hope everyone can get one step closer to good health!
Moet
References
Charron CS, Dawson HD, Albaugh GP, et al. A Single Meal Containing Raw, Crushed Garlic Influences Expression of Immunity- and Cancer-Related Genes in Whole Blood of Humans. J Nutr. 2015;145(11):2448-2455. doi:10.3945/jn.115.215392
Zhou X, Qian H, Zhang D, Zeng L. Garlic intake and the risk of colorectal cancer: A meta-analysis. Medicine (Baltimore). 2020;99(1):e18575. doi:10.1097/MD.0000000000018575
Li Z, Ying X, Shan F, Ji J. The association of garlic with Helicobacter pylori infection and gastric cancer risk: A systematic review and meta-analysis. Helicobacter. 2018 Oct;23(5):e12532. doi: 10.1111/hel.12532. Epub 2018 Aug 28. PMID: 30155945.