Garlic originated in Asia but is now used and cultivated globally. It has a long history of use in most traditional medicine systems to aid in the treatment and prevention of infections, sanitizing wounds and devices and aiding longevity and general health. As a food ingredient it is used globally to enhance flavor, odor and increase shelf life of foods. It is a common ingredient in recipes combined with meat and other sources of animal protein. Such as eggs and dairy.
Garlic has an excellent safety profile with a long history of use and thousands of published papers and scientific studies. Unless you have clotting disorder and / or use blood thinning anti-clotting medication than you should avoid it.
Garlic is a bulb that grows in and on the ground. Like most plants it contains multiple compounds to protect itself from its environment including weather and bacterial or fungal infection, mold, and rot. A number of these compounds have been shown to provide some of the health promoting effects associated with garlic consumption observed over thousands of years via modification of our microbiome.
Garlic modifies the gut flora / microbiome.
Garlic antimicrobial effects
The antimicrobial actions of garlic are especially important if eating a restricted and consistent diet and not eating a varied diet. In nature there are variations in food availability with seasons and natural weather events etc. Regardless of whether you are herbivore, omnivore, or carnivore there are phases of feast and famine. A hunting tribal carnivore cannot access the same fresh meat every day all year round with migrations, hibernations, and seasons. Herbivore’s plants grow in seasons and will only be available for a certain period of time before they need to eat different foods. This is a particularly important process for gut health. If an omnivore eats the same meat, vegetables, and fruit, nuts all year round than they may be technically eating a “balanced diet” but not a varied diet.
Your gut microbiome is determined by your diet and lifestyle. These organisms feed on your food. If you eat only a limited number of foods all throughout the year than you will feed the bugs that love that food and starve the rest. This creates a lack of diversity with an overgrowth of specific microbes and deficiency of others. Once certain bugs overgrow, they displace the deficient bugs and compete with them for food and space.
If the same foods come in long term without break and as such provides the substrate for specific microbes then you need to manage the population total number and diversity through natural dietary antimicrobial compounds and cycling your chosen diet with seasons.
Remember garlic is seasonal too, usually harvested in the summer. But in nature you will find an abundance of antimicrobial compounds found in the skins, peels, seeds, pulps of plants that help to modify gut flora that can be cycled through your diet as they come into season.
One mechanism of action that has been discovered as a link between a high red meat diet with an increased risk of heart disease is the TMAO pathway.
Garlic has a reputation for benefiting the cardiovascular system, partly by its positive effects on the gut microbiome. Lack of diversity and overgrowth of certain microbes in the microbiome may be associated with an increased risk of cardiovascular disease.
Dietary methylamines (choline, carnitine, and phosphatidylcholine) are used by the gut microbiota to produce a range of metabolites, including trimethylamine (TMA).[i] TMA creates trimethylamine oxide (TMAO). TMAO can contribute to atherosclerotic plaques.
Then consider if you eat meat with garlic than the garlic can reduce the overgrowth of the microbes that convert carnitine to bad stuff and allow for the carnitine to be available to your body for fat burning, brain function, energy production etc. instead of feeding your overgrown microbes.
Garlic may help to prevent cardiovascular disease by decreasing TMA and TMAO formation, improving gut microbial diversity, increasing the relative abundance of beneficial bacteria.[ii][iii][iv][v][vi]
Effect of allicin and raw garlic juice on CVD prevention and atherosclerosis amelioration through gut microbiota and TMAO modulation. From: Atherosclerosis amelioration by allicin in raw garlic through gut microbiota and trimethylamine-N-oxide modulation
TMAO smells a bit like fish, microbes on fish convert carnitine to TMA and TMAO and that creates a fishy smell in fish when it is not fresh. Traditionally plant compounds like garlic, tea leaves and citrus peels were used to “marinade” and protect and disguise the fishy odour. This has been shown to work by reducing microbes converting the carnitine.
Garlic prebiotic effects to support microbiome
Prebiotic FOS in Garlic as Garlic fructan (GF) is nearly 75% of its dry weight. GF selectively stimulates the Bifidobacteria proliferation while represses the less desirable Clostridia species, which can support the growth of other pathogens. [i]
Garlic supports healthy commensal microbes like Bifidobacterium and lactobacillus and reduces pathogenic microbes. [ii]
Plants need to protect themselves from infection too. All plants, loose leaf lettuces and leafy herbs are very vulnerable even though they are up off the ground, radishes and other root vegetables, garlic bulbs etc. are on or in the ground and exposed to microbes. Fruits, especially berries are very susceptible. That’s why you will often find antimicrobial compounds in all of them. Especially in the skins, peels, seeds, roots, and outer leaves.
Garlic kills mold, yeast, and fungus which these bulbs are exposed to a lot. You have probably seen mold growing on the outside of garlic but inside is protected. Yeast and fungal infections, and candida overgrowth, can be managed with dietary garlic.
Also kills mold and that led to possibly worst invention ever (IMO) and that was garlic oil used to sterilize toothbrushes.
Many meats contain parasites and can be a source of food-borne parasitic infections. Humans get infected by eating raw or undercooked meat infected with cyst stages of these parasites.[iii]
Antibiotic resistance from the meat industry is horrific. Basically, antibiotics are used prophylactically to prevent infection to maximize carcass yield, (aka prevent weight loss from infections). This runs through our food chain and ecosystem and contributes to antibiotic resistance as well as fungal overgrowth. Allicin from garlic can inhibit the proliferation of bacteria and fungi or kill cells directly, including antibiotic-resistant strains like methicillin-resistant Staphylococcus aureus (MRSA). [iv]
The health of your mouth, gums, and throat microbiome can have a big impact on your overall health, including cardiovascular health. Garlic reduces dental plaque[v] and Garlic prevents oral strep[vi] aka strep throat.
Paradoxically many plant-based or “sulfur-based” compounds that are toxic to certain microbes and may have a “pro-oxidant effect” on infecting organisms can have a “net” protective antioxidant effect to the human host when consumed. For example, certain compounds toxic to microbes induces NRF2 activation that stimulates a cascade of events that support antioxidant and anti-inflammatory defense mechanisms. When the actives from garlic activate NRF2 receptors the body responds by making antioxidant and anti-inflammatory compounds.[vii][viii][ix]
The recommended dosage for garlic that should have sufficient allicin bioavailability potential, is about 2 to 4 g of crushed raw garlic. [i]
Aged garlic, garlic dry powder and garlic oil can all have different profiles of active components, and the dose will vary as an equivalence to the fresh herb.
Garlic can be toxic at high doses. Always consult your healthcare provider before making any changes to your diet and lifestyle. Do not exceed recommended doses.
Garlic should be avoided by some people
This information is not to diagnose, treat or cure any ailment and it does not take the place of any advice you receive from your healthcare provider. This is for information purposes only.
Garlic is good. It makes our food taste better and can help to make our food better for us. There is such a long history of use globally as a regular part of the diet as well as ample modern scientific data suggesting more therapeutic applications to research if you choose to.
Final tip: Tell your special friend to eat it with you so you both have garlic breath and then we are all good.
[i] Nat Med. 2013 May; 19(5): 576–585.Published online 2013 Apr 7. doi: 10.1038/nm.3145PMCID: PMC3650111 NIHMSID: NIHMS450760 PMID: 23563705. Intestinal microbiota metabolism of L-carnitine, a nutrient in red meat, promotes atherosclerosis. Robert A. Koeth et al.
[ii] Microbiome. 2018 Apr 20;6(1):73. doi: 10.1186/s40168-018-0461-0. Metabolic retroconversion of trimethylamine N-oxide and the gut microbiota Lesley Hoyles 1, Maria L Jiménez-Pranteda 2, Julien Chilloux 1, Francois Brial 3, Antonis Myridakis 1, Thomas Aranias 3, Christophe Magnan 4, Glenn R Gibson 2, Jeremy D Sanderson 5, Jeremy K Nicholson 1, Dominique Gauguier 1 3, Anne L McCartney 6, Marc-Emmanuel Dumas 7. PMID: 29678198 PMCID: PMC5909246 DOI: 10.1186/s40168-018-0461-
[iii] l-Carnitine in omnivorous diets induces an atherogenic gut microbial pathway in humans. Robert A. Koeth, … , Jose Carlos Garcia-Garcia, Stanley L. Hazen Published December 10, 2018. Citation Information: J Clin Invest. 2019;129(1):373-387. https://doi.org/10.1172/JCI94601.
[iv] NPJ Biofilms Microbiomes. 2022 Jan 27;8(1):4. doi: 10.1038/s41522-022-00266-3. Atherosclerosis amelioration by allicin in raw garlic through gut microbiota and trimethylamine-N-oxide modulation. Suraphan Panyod et al.
[v] Buffa, J.A., Romano, K.A., Copeland, M.F. et al. The microbial gbu gene cluster links cardiovascular disease risk associated with red meat consumption to microbiota L-carnitine catabolism. Nat Microbiol 7, 73–86 (2022). https://doi.org/10.1038/s41564-021-01010-x
[vi] Proc Natl Acad Sci U S A. 2021 Aug 10;118(32):e2101498118. doi: 10.1073/pnas.2101498118. Elucidation of an anaerobic pathway for metabolism of l-carnitine-derived γ-butyrobetaine to trimethylamine in human gut bacteria. Lauren J Rajakovich 1, Beverly Fu 1, Maud Bollenbach 1, Emily P Balskus 2. PMID: 34362844 PMCID: PMC8364193 DOI: 10.1073/pnas.2101498118
[vii] Exp Ther Med. 2020 Feb;19(2):1472-1478. doi: 10.3892/etm.2019.8374. Epub 2019 Dec 27. Garlic lowers blood pressure in hypertensive subjects, improves arterial stiffness and gut microbiota: A review and meta-analysis. Karin Ried PMID: 32010325 PMCID: PMC6966103 DOI: 10.3892/etm.2019.8374
[viii] Zhang N., Huang X., Zeng Y., Wu X., Peng X. Study on prebiotic effectiveness of neutral garlic fructan in vitro. Food Sci. Hum. Wellness. 2013;2:119–123. doi: 10.1016/j.fshw.2013.07.001.
[ix] Phytomedicine. 2012 Jun 15;19(8-9):707-11. doi: 10.1016/j.phymed.2012.02.018. Epub 2012 Apr 4. Effect of garlic powder on the growth of commensal bacteria from the gastrointestinal tract Angela Filocamo 1, Carmen Nueno-Palop, Carlo Bisignano, Giuseppina Mandalari, Arjan Narbad PMID: 22480662 DOI: 10.1016/j.phymed.2012.02.018
[X] Review Eur J Clin Microbiol Infect Dis
. 2017 Sep;36(9):1531-1540. doi: 10.1007/s10096-017-2965-0. Epub 2017 Mar 22.
Blastocystis: how do specific diets and human gut microbiota affect its development and pathogenicity?
M Lepczyńska 1, J Białkowska 2, E Dzika 3, K Piskorz-Ogórek 4 5, J Korycińska 3
Affiliations expand PMID: 28326446 PMCID: PMC5554277 DOI: 10.1007/s10096-017-2965-0
[xi] Review Molecules. 2014 Aug 19;19(8):12591-618. doi: 10.3390/molecules190812591. Allicin: chemistry and biological properties. Jan Borlinghaus, Frank Albrecht, Martin C H Gruhlke, Ifeanyi D Nwachukwu, Alan J Slusarenko. PMID: 25153873 PMCID: PMC6271412 DOI: 10.3390/molecules190812591
[xii] Comparative Study Indian J Dent Res. . Jan-Feb 2013;24(1):71-5. doi: 10.4103/0970-9290.114957. Antibacterial effect of different concentrations of garlic (Allium sativum) extract on dental plaque bacteria. Behzad Houshmand 1, Faranak Mahjour, Omid Dianat PMID: 23852236 DOI: 10.4103/0970-9290.114957
[xiii] Int J Dent Hyg. 2007 May;5(2):109-15. doi: 10.1111/j.1601-5037.2007.00230.x. Antimicrobial activity of garlic against oral streptococci F C Groppo 1, J C Ramacciato, R H L Motta, P M Ferraresi, A Sartoratto PMID: 17461963 DOI: 10.1111/j.1601-5037.2007.00230.x
[xiv] Review Life Sci. 2020 May 15;249:117513. doi: 10.1016/j.lfs.2020.117513. Epub 2020 Mar 5. Allicin pharmacology: Common molecular mechanisms against neuroinflammation and cardiovascular diseases Feres José Mocayar Marón 1, Alejandra Beatriz Camargo 2, Walter Manucha 3. PMID: 32145307 DOI: 10.1016/j.lfs.2020.117513
[xv] Review Oxid Med Cell Longev. . 2012;2012:907162. doi: 10.1155/2012/907162. Epub 2012 May 17. The antioxidant mechanisms underlying the aged garlic extract- and S-allylcysteine-induced protection. Ana L Colín-González 1, Ricardo A Santana, Carlos A Silva-Islas, Maria E Chánez-Cárdenas, Abel Santamaría, Perla D Maldonado. PMID: 22685624 PMCID: PMC3363007 DOI: 10.1155/2012/907162
[xvi] J Nutr. 2010 Jul;140(7):1211-9. doi: 10.3945/jn.110.121277. Epub 2010 May 12. Ajoene, a stable garlic by-product, has an antioxidant effect through Nrf2-mediated glutamate-cysteine ligase induction in HepG2 cells and primary hepatocytes. Hee Yeon Kay 1, Jin Won Yang, Tae Hyun Kim, Da Yeon Lee, Bomi Kang, Jae-Ha Ryu, Raok Jeon, Sang Geon Kim. PMID: 20463144 DOI: 10.3945/jn.110.121277
[xvii] NARRATIVE REVIEW| VOLUME 40, ISSUE 7, P4807-4819, JULY 01, 2021. From the distinctive smell to therapeutic effects: Garlic for cardiovascular, hepatic, gut, diabetes and chronic kidney disease
Marcia Ribeiro et al. March 09, 2021DOI:https://doi.org/10.1016/j.clnu.2021.03.005
[xviii] Nutrients 2020, 12(3), 872; https://doi.org/10.3390/nu12030872
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