Is Garlic Good for You? Health Benefits, Side Effects & Drug Interactions

Garlic is not only a popular ingredient in cooking, it’s also important in the “food as medicine” holistic health movement because of purported wellness benefits.

Learn about its benefits, its side effects and drug interactions, how much to take and if it may be a safe addition to your wellness plan.

What is garlic?

Garlic is often thought of as a spice or an herb, but it's actually a root vegetable. It's an edible bulb from a plant in the lily family that's commonly used to add flavor to food dishes. Throughout the world, it has long been used to help treat skin and heart issues, according to the U.S. National Center for Complementary and Integrative Health (NCCIH).

Potential health benefits of garlic

“Garlic is a powerful prebiotic that has been proven to have multiple health benefits,” said Megan Hilbert, a registered dietitian and nutrition coach at Top Coaching in Madison, Wis. “Garlic is full of important nutrients like vitamin B6, vitamin C, selenium, fiber [prebiotics] and manganese.”

A research review published in the journal Experimental and Therapeutic Medicine noted that garlic’s prebiotic properties may add to the rich diversity of microbes needed to keep your gut healthy.

The review also noted that several studies found that garlic supplements “significantly” lowered blood pressure and normalized cholesterol levels.

“Some research also shows that garlic can have a positive impact on arteries and blood pressure due to a plant compound called allicin found in garlic," Hilbert said. "Those with high cholesterol can also benefit from garlic.”

In addition, the journal CNS & Neurological Disorders - Drug Targets published a review highlighting how garlic has both antioxidant and anti-inflammatory properties that may provide “remarkable” protection against neurological disorders like Alzheimer’s and Parkinson’s diseases.

“Garlic has anti-inflammatory properties thanks to a compound called diallyl disulfide,” Hilbert said. “The antioxidants in garlic may also help prevent Alzheimer’s disease and dementia due to reduction in oxidative stress.”

Garlic may also benefit the skin, owing in part to its antioxidant properties, according to the Cleveland Clinic. Rubbing it directly on your skin can potentially clear away acne and give your skin a fresh, clean glow.

Safety of garlic

Garlic consumed in the normal portions found in foods is generally considered safe. Little is known about the safety of garlic supplements and topical applications during pregnancy or while breastfeeding, however.

Hilbert said that for a very small number of people, “garlic may … increase the risk of bleeding or cause an allergic reaction.”

Side effects of garlic

One side effect is well known: Eating garlic or taking garlic supplements can cause bad breath and/or body odor.

“Some individuals may also be sensitive to the carbohydrates in garlic, called fructans, especially those who are diagnosed with IBS [irritable bowel syndrome]," Hilbert said. "These can produce uncomfortable GI [gastrointestinal] symptoms like gas, bloating, diarrhea or constipation.”

She added that some may experience upper GI symptoms such as heartburn, reflux and/or GERD (gastroesophageal reflux disease).

The Cleveland Clinic notes that rubbing raw garlic on your skin can cause a burning sensation. Speak with a dermatologist before using it for skin issues, especially if you're using other skin products.

Potential drug interactions of garlic

“Some HIV medications [such as] saquinavir is known to interact with garlic, and may decrease the effects of this medication,” Hilbert said. “Other medications like blood thinners, liver medications or blood pressure medications may also be impacted by garlic.”

According to St. Luke’s Hospital in Chesterfield, Mo., garlic may also interact with:

• Birth control pills, making them less effective
• The tuberculosis medication isoniazid
• Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen and naproxen
• Other herbs and supplements

Dosage

A typical dose to help reduce inflammation, support gut health (if you aren't diagnosed with IBS) and support general health is 2 to 5 grams of fresh, raw garlic a week, Hilbert said.

“For high cholesterol, a large meta-analysis showed that 300 mg three times daily, or 250 mg of aged garlic daily over 12 weeks improved HDL cholesterol and plasma triglycerides,” she said.

To reduce high blood pressure, Hilbert said that some research indicates you should take two 240 mg garlic capsules a day, while other research suggests taking up to 2,000 mg a day.

What a dietitian says

Overall, is garlic good for you?

“There has been lots of high-quality data covering the impacts garlic has on numerous health conditions,” Hilbert said. “Some conditions [such as] cancer, liver disease [and] diabetes need more data to have conclusive evidence of garlic’s impact. Most evidence supporting the use of garlic is for conditions like high cholesterol and hypertension [high blood pressure].”

Bottom line

While garlic has many potential wellness benefits, it’s also important to understand its potential risks, Hilbert said.

“As always, it's important to speak with your doctor before adding in high-dose garlic supplements, especially if you are on any current medications as they can have strong reactions,” she advised.

SOURCE: Megan Hilbert, MS, RDN, registered dietitian, Top Coaching, Madison, Wis.

References

U.S. National Center for Complementary and Integrative Health: Garlic

Experimental and Therapeutic Medicine Journal: Garlic lowers blood pressure in hypertensive subjects, improves arterial stiffness and gut microbiota: A review and meta-analysis

CNS & Neurological Disorders - Drug Targets: Pharmacotherapeutic Potential of Garlic in Age-Related Neurological Disorders

Cleveland Clinic: Health Benefits of Garlic

St. Luke’s Hospital: Garlic: Allium Sativum