The Medicinal Value of Garlic

For healing with food, it’s hard to do better than garlic, which can help with osteoarthritis, lower high blood pressure naturally, and much more.

crushing garlic

Crushing garlic cloves and letting them sit a few minutes before cooking can preserve their health benefits.

Photo by iStock

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How many of your salad dressing ingredients were once worshipped as a god and used as ancient currency? Probably only one: The glorious garlic bulb. Worshipped and used as money in ancient Egypt, garlic has been credited with warding off everything from the Black Plague to vampires. Despite its heady history, this flavorful and versatile herb is plentiful, inexpensive and a cinch to grow.

Garlic is a member of the Allium family, which also includes onions, scallions, chives and leeks. Its earthy flavor complements almost any cuisine, and it’s used heavily around the world. While in the United States we consume a decent amount of garlic—about two pounds each per capita—in countries such as Italy, Korea and China, where garlic is used liberally in the diet and seems to be protective against disease, per-capita consumption is as high as eight to 12 cloves a day, according to The New York Times.

When it comes to health, there isn’t just one reason to love garlic, but many, including its proven abilities to help combat some of the world’s most common killers, such as cardiovascular disease, cancer and obesity, all while boosting the immune system to help fight ailments as mundane as the common cold. In fact,, the U.S. National Library of Medicine run by the National Institutes of Health, includes about 5,000 garlic research studies. 

It’s amazing that something as simple as garlic could confer so many possible disease-repelling and life-extending benefits. Garlic owes its multifaceted health properties to the fact that “it’s such a potent antimicrobial (for most microbes), a great antioxidant (useful for good cardiovascular health) and a nice digestive stimulant,” says Sheila Kingsbury, a licensed naturopathic physician and chair of botanical medicine at Bastyr Center for Natural Health in Kenmore, Washington. In studies performed at the University of Alabama at Birmingham, researchers found that eating garlic helps boost our natural supply of hydrogen sulfide, an antioxidant that transmits cellular signals that relax the blood vessels and increase blood flow, The New York Times reports. This increased hydrogen sulfide production may explain garlic’s ability to protect the heart and help ward off a variety of cancers.

Kingsbury frequently uses garlic therapeutically with her patients. She often uses it in conjunction with probiotics to treat gastrointestinal yeast or, which is an imbalance in intestinal bacteria. She also employs garlic for cardiovascular health to improve lipid status (fat levels in the blood) and circulation. Kingsbury prefers freeze-dried encapsulated garlic or chopped raw garlic, usually mixed into salad dressing or other foods to make it more palatable.

“I also will have patients take garlic internally to treat a variety of infections,” she says. “I have many stories of various skin infections resolved with garlic.”

Garlic & Our Health

Here’s a quick overview of some of garlic’s astounding health benefits:

1. Cancer

Garlic helps fight several types of cancer. In fact, garlic (and other healthy foods) can help prevent and treat liver cancer—exciting news given liver cancer’s high mortality rate. In addition, a recent Chinese study linked raw garlic consumption with reduced risk of lung cancer.

The American Institute for Cancer Research (AICR) reports that garlic could help ward off stomach, skin, colon and lung cancers. Garlic’s cancer-fighting substances include quercetin, a flavonoid with anti-inflammatory and antioxidant properties; allixin, an antimicrobial substance; and allicin, which promotes cell death, inhibits cell growth, and is a major precursor of sulfur compounds.

Likewise, the National Cancer Institute cites numerous population studies that show an association between increased garlic intake and reduced risk of certain cancers. In the European Prospective Investigation into Cancer and Nutrition, an ongoing multinational study investigating the effects of nutrition on cancer, higher intakes of onion and garlic were associated with reduced risk of intestinal cancer. In the Iowa Women’s Study, a study of more than 40,000 women, findings have shown a strong association between increased garlic consumption and reduced colon cancer risk—women who consumed the most garlic had a 50 percent lower risk than those who consumed the least. Other studies from across the world confirm a reduced risk of stomach, esophageal, prostate, pancreatic and breast cancers.

2. Cardiovascular Disease

Garlic has a long history of use for cardiovascular disease; in fact, a 3,500-year-old Egyptian document cites it as useful for heart disorders. Modern science has seen success in both in vitro and clinical trials, although studies are difficult to compare as there are so many variables in the preparation and constituents of the garlic products used, as well as the fact that cardiovascular disease itself is complex and is characterized by multiple factors. To attempt to sort out the wide array of data, researchers from Germany and Austria conducted an “umbrella review”—a review of all published meta-analyses, which are themselves a review of multiple studies—on the garlic studies available on PubMed. They summarize: “Garlic preparations as well as garlic exerted some positive effects on indicators and biomarkers of cardiovascular disease, typically without causing any serious side effects.”

3. Hypertension

About 30 percent of adults worldwide have hypertension, or chronic high blood pressure, which can be an indicator of future heart attacks or strokes. In a recent study, 88 hypertensive individuals took aged garlic extracts (AGE) for 12 weeks. The researchers reported that AGE reduces peripheral and central blood pressure in patients with uncontrolled hypertension. AGE also has the potential to improve arterial stiffness and other cardiovascular markers.

4. Osteoarthritis

According to researchers at King’s College London and the University of East Anglia, women who consume a diet high in alliums, including garlic, onions and leeks, have a lower incidence of hip osteoarthritis. In another study of more than 1,000 women, a research team investigated dietary patterns and x-ray images capturing the extent of early osteoarthritis. In the lab, the investigators found that the garlic compound diallyl disulphide limits cartilage-damaging enzymes when introduced to a human cartilage cell-line. Therefore, researchers conclude that not only does dietary intake of garlic provide some protective benefit, but that extracts of garlic may prove helpful in the development of new treatments for the disease.

5. Immune system

Many studies have underscored garlic’s immune-boosting abilities. Its more than 100 sulfuric compounds are responsible for its ability to wipe out bacteria and infection, so powerful it was used to prevent gangrene in both world wars. Although we’ve long known that garlic can help fight infections, researchers only recently examined garlic’s ability to improve outcomes in treatment of pathogens that are resistant to conventional antibiotics. The study found that a fresh garlic extract could improve the antibiotic sensitivity of these pathogens, making treatment more effective. And there’s good news for sufferers of more common illnesses, too—scientists found in 2012 that AGE was able to influence immune cell function, reducing severity of colds and flus.

6. Diabetes

While garlic has long had a reputation for aiding in the treatment of diabetes, modern science is only starting to gather data on its effectiveness for this chronic disorder. Researchers are learning that garlic does indeed improve insulin sensitivity and other associated metabolic syndromes, at least in animals. Garlic is also able to significantly lower fasting blood glucose, a related issue, according to a meta-analysis of seven clinical trials. In one study, researchers split rats into three groups: One ate cornstarch, one ate glucose, and one ate glucose along with a fresh garlic paste. At the end of eight weeks, levels of serum glucose, insulin, triglycerides and uric acid were all significantly increased in the glucose group as compared with the cornstarch group. However, the rats fed glucose and garlic saw a significant reduction in all of these levels, as well as insulin resistance, compared with the glucose-only rats. This study effectively demonstrates that “raw garlic homogenate is effective in improving insulin sensitivity while attenuating metabolic syndrome and oxidative stress in glucose-fed rats,” researchers summarized.

7. Prebiotic

Mounting research points to the critical importance of maintaining a healthy mix of bacteria in our bodies—beneficial bacteria, or probiotics, are thought to do everything from aiding digestion to improving mood and mental health. Like any living thing, probiotics need food to thrive, and this is where prebiotics come in. Prebiotics act as food for gut bacteria, and raw garlic is among the best options for feeding the little guys. Other good prebiotics include raw onion, raw leeks, raw asparagus, whole-wheat flour and bananas.

8. Liver damage

Animal studies suggest more research could be useful to investigate garlic’s ability to protect the liver. In one study, researchers tested whether a bioactive compound in fresh garlic paste could help protect against liver damage from acetaminophen, a popular pain reliever, and found that the garlic did indeed help protect this important organ from damage. In another study published in Nutrition Reviews, Australian researchers found that, because of its ability to reduce total serum cholesterol and low-density lipoprotein cholesterol levels, regular garlic consumption may protect against fat accumulation in the liver.

Try cooking with garlic using these recipes:

Spinach with Pan-Roasted Garlic
Garlic Aioli
Garlic and Olive Tapenade

Learn how to incorporate garlic into your lifestyle in Garlic Tablet Benefits and Supplement Advice.

Letitia L. Star is a natural health and home writer who has written more than 1,100 articles, including many features on health, healthy eating, gardening and homes.