Garlic for Gut Health


Garlic as a medicinal ingredient has been used since ancient Egypt. Historically garlic was used during WWII to treat gangrene. During a severe flu-season in the former Soviet Union, 500 tons of whole cloves were imported to the region for acute treatment. The history of this culinary gem is fascinating on its own. However, you will be surprised to learn how much this common ingredient has been studied.

Garlic contains many components but the most studied is allicin. Allicin is derived from crushed whole garlic and is responsible for garlic’s distinct smell. It can also be found in dried garlic that is reconstituted. Allicin has been pinpointed as the workhorse component of garlic. Trials using garlic supplementation without allicin show few to no positive health benefits.

Allicin is sensitive to pH and is liberated at levels above 4.4 pH. A common practice is ingesting whole garlic cloves as you would a pill. This however is ineffective as stomach pH is too low to activate allicin. Whole garlic should then be consumed crushed and in the presence of other foods to increase the stomach pH and allow allicin formation. With this in mind, take care when choosing a garlic supplement. Choose one that is enteric coated and take with food to minimize inactivity through too low a pH.

Garlic to Reduce Inflammation

In animal and cell studies, garlic has shown to be a potent antioxidant and is protective against vascular injury. Still other studies show reductions in blood pressure and prevention of blood clotting with whole garlic or allicin administration. Mechanistically, allicin can inhibit nuclear factor-kappaB, a cellular factor that triggers inflammatory pathways. In addition to this inhibition, allicin can stimulate protective pathways via interaction with Nrf2. Nrf2 is a protein that binds to genes that code for enzymes that protect against oxidative stress and inflammation. In this way, many consider Nrf2 to be a master switch, and is implicated in numerous chronic, inflammatory diseases. Many nutritional components in addition to garlic can influence Nerf2 including curcumin and resveratrol.

Garlic for Immunity

Garlic extracts can be potent anti-virals and anti-microbials. Its anti-bacterial properties were first discovered by none other than Louis Pasteur. Regular consumption of garlic is believed to influence the immune response, by stimulating lymphocytes, macrophages, and natural killer cells. Garlic has also been shown to inhibit Th1 immune responses (associated with IBD) and inflammatory cytokines while regulating the anti-inflammatory IL-10.

Cytomegalovirus, rhinovirus type 2, herpes simplex types 1 and 2, and influenza B are well known to be susceptible to garlic both in vitro and in vivo. However, anti-viral properties of whole garlic come from a different component, ajoene. Ajoene is lipid soluble and liberated from the garlic clove with oil maceration.

A rather impressive double-blind, placebo controlled study used 146 subjects to assess the efficacy of garlic supplementation for cold prevention. The treatment group (180mg allicin) experienced significantly fewer colds during the 12-week period, and recovered faster when cold was experienced.

Garlic for Gut Disorders

Garlic is perhaps best for those with chronic gut issues of overgrowth including dysbiosis, candida, IBD, and H. pylori. Garlic can complement the effects of antibiotics for a more effective eradication. Garlic can also reduce bacterial biofilm formation and prevent bacteria aggregation. This effect was even shown in studies of hospital acquired MRSA on medical devices. Garlic is effective against yeast and other fungi—and works synergistically with prescribed anti-fungals. The mechanism by which allicin is able to interfere with bacteria and fungi is believed to be due to blocking enzymes (thiol-containing) in the micro-organism to prevent growth. These chemical properties protect the garlic bulb from micro-organisms in the surrounding soil.

Be sure to include garlic in your daily meals. If you are not a fan, consider regular garlic supplementation. Those with gut issues are also advised to consume and supplement with garlic to balance flora.

For anti-microbial effects in the gut, dose high. Consume garlic daily in food preparation. Nutritional bodies recommend a modest 4g of garlic daily, which is equivalent to one large size clove. Higher doses are suggested for gut disorders but caution should be used for those on blood thinners.

But the smell…

In writing this post I was surprised to find research studies that assess body odor associated with garlic consumption. Most surprising is that these studies have found scents of frequent garlic consumers more pleasant than the garlic adverse. Even breastfed babies show increased suckling time from mother’s that consume garlic supplements compared to those that don’t. It is also thought that regular consumption reduces skin pungency over time. Still not a garlic fan? Lucky for you many supplements are designed to be odor free. For everyone else, I suggest we just embrace our garlic odor.


Lawson & Hunsaker (2018) Allicin Bioavailability and Bioequivalence from Garlic Supplements and Garlic Foods. Nutrients. 10(7): 812.

Cardozo, L. F. M. F., et al. (2013). Nutritional strategies to modulate inflammation and oxidative stress pathways via activation of the master antioxidant switch Nrf2. Biochimie, 95(8), 1525–1533.

Ankri, S., & Mirelman, D. (1999). Antimicrobial properties of allicin from garlic. Microbes and Infection, 1(2), 125–129.

Josling, P. (2001) Preventing the common cold with a garlic supplement: A double-blind, placebo-controlled survey. Advances in Therapy. 18:4: 189–193.

Marchese, A., et al. (2016). Antifungal and antibacterial activities of allicin: A review. Trends in Food Science & Technology, 52, 49–56.

Fialová, J., Roberts, S. C., & Havlíček, J. (2016). Consumption of garlic positively affects hedonic perception of axillary body odour. Appetite, 97, 8–15.