What are the health benefits of garlic? How does it impact aging? How do I supplement with garlic? These questions and more are answered here.

What is garlic?

Garlic is a plant in the lily family that produces a fragrant bulb that nearly every world culture has used as a medicinal herb for thousands of years. The sulfuric compounds found in the cloves contain a multitude of therapeutic properties.

Garlic can be found in several forms, such as fresh, powdered and aged.

The health benefits of garlic for disease prevention

Some of the health benefits of garlic include:

  • Builds immunity
  • Reduces atherosclerosis and platelet aggregation, promoting cardiovascular health
  • Destroys harmful bacteria (gastrointestinal)
  • Reduces age-related chronic illnesses, such as free radical damage as it relates to Alzheimer’s disease and cancer

For decades cardiovascular disease has had the highest mortality worldwide compared to all other health problems, and it can be attributed to numerous causes. The health benefits of garlic is that it addresses at least two of them.

Garlic’s organosulfur compounds have been found to reduce the degree of cholesterol synthesis by the liver. (Reference 5) It also inhibits platelet aggregation.

A trial that measured participants’ blood pressure after consuming aged garlic for 12 weeks found one of the health benefits of galic was that it lowered systolic levels higher than 140 by 10 points, which compares to conventional treatment. (Reference 9) Additionally, a review of 11 studies that tested garlic’s blood pressure-lowering effects found that in all cases it was significantly more effective than the placebo. (Reference 10)

The immune system’s effectiveness can decrease steadily as we age, which is evidenced by the strong ties between influenza and shingles infections in older populations. (Reference 7)

Garlic stimulates ‘T helper’ and ‘natural killer’ cell activity, which can markedly improve the body’s defense system. (Reference 8)

The antimicrobial activity of garlic is effective against bacterial infections and reducing the level of harmful organisms in the intestines, according to a 2011 study. Researchers found that rats induced with the Salmonella typhi bacteria and then fed garlic saw markedly reduced intestinal infection and disease duration, which perpetuates its traditional reputation as a digestive balancer. (Reference 11)

Garlic and aging

Oxidation is an additional age-related disease precursor, which environmental pollutants and the over-burdening of the body’s natural stores of antioxidants exacerbate.

Cellular metabolism, or the multitude of chemical reactions necessary to maintain cell functioning, creates harmful waste or free radicals,  which the body ordinarily neutralizes with its stores of antioxidants.

In modern times, however, the sheer high-level load of toxins in the environment and that result from stress increase the number of healthy DNA mutations free radicals cause. If these are left untreated, they replicate and develop disease. To compensate for the extra oxidation damage, supplementing with dietary or nutraceutical antioxidants is necessary to prevent cancer, heart disease, Parkinson’s and Alzheimer’s disease.

A large number of studies have demonstrated that another one of the health benefits of garlic, particularly aged garlic, is fighting against oxidative stress. (Reference 1)

In a study of mice induced with Alzheimer’s disease and fed aged garlic, researchers found garlic prevented memory deterioration and concluded the herb may be effective for impeding the disease’s progression. (Reference 2) (Alzheimer’s disease is the most common form of mental impairment in older people.)

Cancer is a leading cause of death worldwide, accounting for 7.6 million deaths in 2008, and the risks increase dramatically with age. (Reference 6) In a 2011 review of a number of cancer studies that incorporated medicinal garlic use, researchers found it suppressed precancerous and cancerous cell development, induced cancerous cell death and inhibited tumor growth. (Reference 12)

Can I get enough garlic in my diet?

Garlic provides only four calories per clove and is too small in size to demonstrate significant macronutrient value, so concerns regarding consuming it are ordinarily about its flavor and therapeutic value. For raw garlic, the two criteria are linked; the strong flavor is the result of active organosulfur compounds.

Here’s a tip: Avoid heating it and always mince or crush it to release the medicinal oils. (Reference 5)

Supplementing with garlic

Fresh garlic: 2-4 g per day of fresh, minced garlic cloves (one clove equals one gram). (Fresh garlic should be stored in a cool, dry place for as long as three weeks.

Powdered garlic: 200 mg, 2 tablets 3 times daily

Aged garlic: 600-1,200 mg daily in divided doses

There is a wide variation in the level of active ingredients among garlic supplement forms. To remedy this problem and provide consistent therapeutic results, manufacturers produce formulas standardized to a determined level of S-allyl cysteine, which is a sulfur compound that results from the activation of allicin. The aged garlic supplement type is typically stronger compared with other types.

Side effects of garlic

Despite a range of health benefits of garlic, there are some side effects, including headache, fatigue, strong odor, gastrointestinal upset, low blood sugar and blood thinning.

Absorption when supplementing with garlic

Enteric-coated garlic supplements are common because they improve the release and absorption of active ingredients; the coating circumvents contact with stomach acid. (Reference 4)

Divided dosage

The studies recording the health benefits of garlic, such as treating and preventing disease, utilized divided doses because gastrointestinal, taste and odor reactions resulting from the herb’s pungency indicated a more-than-one dose beneficial.

Testing garlic levels

Some properties of garlic are unclear to researchers, such as its disappearance from body chemistry after ingestion. No researcher has ever registered traces of garlic compounds in the body’s chemistry following supplement use, even after the consumption of 25 g.

The organosulfur compounds may be rapidly metabolized and instead of using blood levels as biomarkers, the breath odor is a sign of bioavailability or overuse when strong or offensive.


Garlic may contraindicate with the function of particular prescription medications, effecting absorption, effectiveness or potency of the following: (Reference 3)

  • Isoniasid (tuberculosis medication)
  • Birth control pills
  • Blood-thinning medications
  • Medications for HIV/AIDS


  1. Colin-Gonzalez, Ana L., et al. Oxidative Medicine and Cellular Longevity
    “The Antioxidant Mechanisms Underlying the Aged Garlic Extract- and S-Allylcysteine-Induced Protection.” January, 14, 2012.
  2. Chuahan, Nelima B. Phytotherapy Research. “Amelioration of Early Cognitive Deficits by Aged Garlic Extract in Alzheimer’s Transgenic Mice.” March 23, 2007. http://onlinelibrary.wiley.com/doi/10.1002/ptr.2122/abstract
  3. University of Maryland Medical Center. Garlic. January 26, 2011. http://www.umm.edu/altmed/articles/garlic-000245.htm
  4. Lawson, L.D., et al. Journal of Agricultural and Food Chemistry. “Low Allicin Release From Garlic Supplements: A Major Problem Due To The Sensitivities Of Alliinase Activity.” http://www.ncbi.nlm.nih.gov/pubmed/11368641
  5. Linus Pauling Institute. Garlic and Organosulfur Compounds. http://lpi.oregonstate.edu/infocenter/phytochemicals/garlic/#sources
  6. World Health Organization. Cancer. February 2012. http://www.who.int/mediacentre/factsheets/fs297/en/
  7. Life Extension Magazine. Naturally Boosting Immunity During Cold Season. November 2006.http://www.lef.org/magazine/mag2006/nov2006_report_immunity_01.htm?source=search&key=immune%20system%20aging
  8. Smith, Jim, et al. Functional Food Product Development. 2010. Page 305. http://books.google.com/books?id=unIv6t6FdbcC&printsec=frontcover#v=onepage&q&f=false
  9. Ried, Karin, et al. Maturitas. “Aged Garlic Extract Lowers Blood Pressure in Patients with Treated but Uncontrolled Hypertension: A Randomised Controlled Trial.” October 2010.http://www.sciencedirect.com/science/article/pii/S0378512210002276
  10. Ried,  Karin, et  al. BMC Cardiovascular Disorders. “Effect of Garlic on Blood Pressure: A Systematic Review and Meta-Analysis.”  June 2008. http://www.biomedcentral.com/1471-2261/8/13/
  11. Adebolu, T. T., et al. African Journal of Biotechnology. Effect of Garlic (Allium sativum) on Salmonella Typhi Infection, Gastrointestinal Flora and Hematological Parameters of Albino Rats.  July 2011. http://www.academicjournals.org/AJb/full%20text/2011/13Jul/Adebolu%20et%20al.htm
  12. Herman-Antosiewicz, Anna, et al. Anti-cancer Evidence-based Materia Medica. “An Evidence-based Perspective of Allium Sativum (Garlic) for Cancer Patients.”  2011.
  13. Chuahan, Nelima B. Phytotherapy Research. “Amelioration of Early Cognitive Deficits by Aged Garlic Extract in Alzheimer’s Transgenic Mice.” March 23, 2007.  http://onlinelibrary.wiley.com/doi/10.1002/ptr.2122/abstract

Last reviewed 10/Feb/2017


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