Young Ju, Ph.D.

Garlic has been used as a spice, food, and medicine for thousands of years all over the world. At the present time, garlic is one of the most commonly used dietary supplements for addressing high cholesterol and high blood pressure.  Besides warding off vampires, what can garlic and garlic products do for your health?

Garlic and Its Nutrients 

In the US, the average person consumes about 2 pounds per year (1) compared to about 31 pounds in China, the top consumer and producer.  About 75% of garlic consumption in the US is in the dried garlic form (2).

Raw garlic cloves contain a sulfur-containing substance, alliin. When a garlic clove is crushed, chopped, or minced, an enzyme (called alliinase) in garlic converts alliin into allicin which produces garlic’s characteristic pungent odor and is considered responsible for the biological activities of garlic.  Note that cooking destroys the alliinase enzyme.  (After cooking, the biological benefits accruing to crushed garlic remain, but not in uncrushed garlic.)  Garlic also contains other nutritional components that could contribute to heart health including dietary fiber, vitamins (C, A, B1, B2, B3, B6, B9, and B12), minerals (calcium, iron, potassium, magnesium, zinc, and selenium), and enzymes (3).

Health Benefits of Garlic and Garlic Products

Research studies have reported numerous health benefits of garlic (4):

• Antioxidative

• Cholesterol lowering

• Anti-atherosclerotic

• Anti-blood clotting

• Blood pressure lowering

• Anti-inflammatory

Due to these potential benefits, it has been suggested that garlic could help prevent cardiovascular diseases, and garlic and garlic products have been evaluated for heart health. While there are mixed results, the most consistent result is that supplementation for longer than 8 weeks with garlic and garlic products (5, 6, 7, 8):

• reduced total cholesterol and LDL-cholesterol (bad cholesterol) levels by 10-15%.

• reduced fatty plaque build-up in arteries (atherosclerosis).

• did not affect HDL-cholesterol and triglyceride levels.

Potential Adverse Effects

Garlic is considered safe for most people to consume in foods. Excessive consumption can cause bad breath, body odor, acid reflux, and digestive issues.

Most garlic supplements are well tolerated. However, garlic supplements may increase the risk of bleeding for people who take an anticoagulant or may increase bleeding post surgery. It has been also reported that garlic supplements may inhibit the effectiveness of a certain HIV drug called protease inhibitor (9).

Garlic Products and Supplements

Many people are averse to eating raw garlic due to its pungent taste and odor.  The food and supplement industries have tried to process garlic into different forms to reduce these negative attributes but still keep the positive ones.  

Garlic Products: These forms include garlic powder, garlic oil, macerate, aged garlic, and garlic extract, etc. These products contain the sulfur-containing compounds, alliin, allicin, and others and maintain their biological benefits in varying degrees.  Commonly used garlic powder, for example, maintains its allicin-derived biological activities if crushed raw garlic is dried. 

Garlic Supplements:  Commercially available garlic supplements may contain garlic powder, oil, or garlic- aged garlic-extracts in various forms, tablet, gel, powder, liquid, and oil, etc. These products are usually odorless and also claim heart health, anti-oxidant, and anti-inflammatory benefits.  In the Supplement Fact panels on the packaging, some products list the amounts of garlic or garlic oil, some list allicin or alliin contents, and some list all sulfur-containing compounds.  

A time-release garlic powder supplement is also available. This type of supplement is designed to release allicin slowly over time within the body rather than all at once.  While the biological effects of garlic and most garlic products last for 4-6 hours in the body after consumption, time-release products last for 12-16 hours (10).

Although there is no official recommendation for how much garlic we should eat, studies suggest that 1-2 cloves per day (containing 6-12 mg allicin), 300 mg in dried garlic tablet form (~1.8 mg allicin) 2-3 times per day, or 7.2 g of aged garlic per day may have health benefits (11).

Overall

Garlic is a good food source for heart health. Crushed raw garlic provides the highest amount of allicin, a biologically active compound. Cooked crushed garlic and processed garlic products could also provide allicin-derived biological activities. Studies demonstrated that garlic and garlic products can lower cholesterol levels, which may lower the risk of heart disease.  Remember also that it is important to read fact panels on any supplements.

REFERENCES

1. PennState Extension. Garlic Production https://extension.psu.edu/garlic-production#:~:text=Garlic%20consumption%20has%20quadrupled%20in,of%20around%20400%20million%20pounds.

2. Agricultural Marketing Resource Center. https://aic.ucdavis.edu/wp-content/uploads/2019/01/agmr-profile-Garlic-2006B.pdf 

3. U.S. Department of Agriculture. Garlic, raw. https://fdc.nal.usda.gov/fdc-app.html#/food-details/169230/nutrients

4. Bayan, L., Koulivand, P.H., Gorji, A. Garlic: a review of potential therapeutic effects. Avicenna J Phytomed. 2014, 4(1): 1.

5. Cicero, A.F.G., Fogacci, F., Colletti, A. Food and plant bioactives for reducing cardiometabolic disease risk: an evidence based approach. Food Funct. 2017, 8:2076.

6. Karagodin, V.P., Sobenin, I.A., Orekhov, A.N. Antiatherosclerotic and cardioprotective effects of time-released garlic powder pills. Current Pharma. Design 2016, 22:196.

7. Kimura, S., Tung, Y.C., Pan, M.H., Su, N.W., Lai, Y.J., Cheng, K.C. Black garlic: A critical review of its production, bioactivity, and application. J Food Drug Analysis 2017, 25:62.

8. Osadnik, T., Golawski, M., Lewandowski, P., Morze, J., Osadnik, K. Pawlas, N., Lejawa, M., Jakubiak, G.K., Mazur, A., Schwingschackl, L., Gaslor, M., Banach, M. A network meta-analysis on the comparative effect of nutraceuticals on lipid profile in adults. Pharma. Res. 2022, 183:106402. 

9. Examine. Garlic. https://examine.com/foods/garlic/

10. Myasoedova, V.A., Ivashinnikova, G.A., Sobenin, I.A., Ivanova, E.A., Orekhov, A.N. Blood Serum Atherogenicity: Cellular Test for the Development of Anti-Atherosclerotic Therapy. Current Pharmaceutical Design. 2017, 23:1195.

11. American Family Physician. Health Effects of Garlic. https://www.aafp.org/pubs/afp/issues/2005/0701/p103.html#:~:text=Dosages%20generally%20recommended%20in%20the,aged%20garlic%20extract%20per%20day.

People with high cholesterol and at risk of heart disease should talk to their healthcare providers about heart health management strategies. This information is provided for your reference and you use at your own risk; you should rely on your medical professional for medical advice.