Garlic has been used for centuries as both a food ingredient and a medicine. Over the years, there has been a lot of interest in using garlic to get rid of harmful bacteria. In this article, we’ll take a look at the scientific evidence on whether garlic has antibacterial properties.
What are the active compounds in garlic?
When a garlic clove is crushed, chopped, or chewed, an enzyme called alliinase is activated. This enzyme converts a compound called alliin into allicin, which is thought to give garlic its antibacterial effects.
Allicin is unstable and quickly converts into other sulfur-containing compounds like diallyl disulfide. So in reality, allicin isn’t present for very long when garlic is used. However, these other compounds may also have antibacterial effects.
In addition to allicin, garlic contains other plant compounds like flavonoids and saponins that may support its antibacterial properties.
What does the research say about garlic and bacteria?
A number of studies have looked into the antibacterial effects of fresh garlic extracts, as well as various garlic supplements:
- Lab studies show that garlic exhibits antibacterial activity against common foodborne pathogens like Salmonella, E. coli, and Staphylococcus aureus. It may also be effective against drug resistant bacteria like MRSA.
- One study found fresh garlic extract was effective against strains of Streptococcus bacteria, including groups A, B, C, and G. However, activity was strongest against group B.
- Aged garlic extract has been shown to inhibit the growth of Helicobacter pylori, a bacteria that can cause ulcers and increase the risk of stomach cancer when present in the gut for a long time.
- Garlic extracts can suppress the growth of oral pathogens like Porphyromonas gingivalis and Prevotella intermedia, which are involved in periodontal disease.
- Applying garlic extracts to infected wounds in mice decreased bacterial colonization of wound sites and enhanced wound healing.
- Some studies show combining garlic with antibiotics like ciprofloxacin or gentamicin results in a synergistic antibacterial effect.
However, not all studies agree that garlic has antibacterial properties. Some found no effect of garlic extracts against different strains of bacteria.
Overall, the research suggests that garlic may help get rid of some types of harmful bacteria. However, effects can vary a lot depending on the specific type and dose of garlic, as well as the species of bacteria involved.
How does garlic compare to antibiotics?
Research shows that garlic has antibacterial activity against some antibiotic-resistant bacteria. But how does it compare head-to-head against antibiotics?
One study tested garlic extract against the antibiotics ampicillin, chloramphenicol, ciprofloxacin, and methicillin against multi-drug resistant strains of S. aureus, E. coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa.
Garlic was most effective against E. coli, with antibacterial activity comparable to ciprofloxacin. It was moderately effective against S. aureus, but much less effective than the other antibiotics.
For K. pneumoniae and P. aeruginosa, garlic extract had minimal antibacterial activity, while the antibiotics were much more potent.
Another study compared a concentrated garlic extract to the antibiotics penicillin, streptomycin, and chloramphenicol. Garlic extract was effective against Salmonella and E. coli, but generally less potent and slower acting than the antibiotics.
While garlic has shown some promise against antibiotic-resistant bacteria, it’s important to keep in mind that different preparations may have varying strengths. Overall, garlic is unlikely to replace antibiotics anytime soon.
Should garlic be used to treat bacterial infections?
Based on the research, garlic does appear to have some antibacterial activity, particularly against certain types of bacteria. However, there are a few important things to keep in mind:
- Human studies are needed to confirm many of garlic’s proposed antibacterial effects.
- Garlic compounds appear less potent than conventional antibiotics against common bacterial pathogens.
- Garlic’s effects can vary substantially depending on preparation, dosage, and type of bacteria.
- Garlic should not be relied on as a stand-alone treatment for serious bacterial infections requiring antibiotic therapy.
That said, adding more garlic to your diet probably won’t hurt if you’re fighting off a minor infection. Some even recommend garlic supplementation to help prevent recurrent conditions like urinary tract infections (UTIs).
However, the best way to use garlic is alongside antibiotics or other treatments prescribed by your doctor. Do not attempt to replace recommended medications with garlic.
Does garlic have any antibiotic side effects?
Garlic is generally recognized as safe by major health agencies. But some people do experience side effects when consuming large amounts:
- Odor: Garlic’s pungent odor is notoriously hard to get rid of. Consuming garlic can cause bad breath and body odor.
- Heartburn: Garlic can trigger heartburn in some people.
- Gas and bloating: Significant amounts of garlic can lead to gas, abdominal pain, and diarrhea.
- Allergic reactions: Garlic allergies are uncommon but can cause symptoms like skin rash, itching, and swelling.
- Bleeding: Large doses may increase bleeding risk, especially before surgery.
- Liver damage: Long-term, high-dose garlic supplements may harm the liver.
To reduce side effects, start with small doses and avoid taking garlic supplements on an empty stomach. Speak to your healthcare provider before increasing your intake if you take any medications.
Should you take garlic supplements?
Dietary garlic comes in several different forms:
- Fresh cloves
- Powdered garlic
- Garlic oil
- Aged, concentrated garlic extracts
Some research shows freshly crushed garlic has the most potent antibacterial effects. However, preparing homemade garlic extracts is time consuming.
Commercially available garlic supplements contain concentrated, stabilized garlic extracts. They are highly standardized and generally more potent than garlic in food.
While garlic supplements may provide antibacterial benefits, consult your doctor before using them as an antibiotic alternative. The optimal dosage for bacterial infections is unknown.
Tips for cooking with garlic
Here are some quick tips for getting the most out of garlic:
- Crush or slice garlic and let it rest for 10 minutes before cooking. This allows time for the antibacterial allicin to form.
- Add garlic towards the end of cooking for the strongest flavor and effects.
- Cooking garlic whole, with minimal chopping, may help retain some antibacterial compounds.
- Pair garlic with herbs like oregano and spices like black pepper, which may also have antimicrobial effects.
- Store fresh garlic in a cool, dry place and away from sunlight.
The bottom line
Here is a summary of the key points:
- Lab studies show garlic has antibacterial activity, particularly against common foodborne pathogens.
- Some research suggests garlic may help fight dental plaque and bacteria like H. pylori.
- However, human studies are lacking for many proposed applications.
- Garlic appears less potent than antibiotics against common bacterial infections.
- Severe bacterial infections should be treated with antibiotics prescribed by a healthcare professional.
- Supplemental garlic may provide additional antibacterial benefits when used alongside antibiotics.
- Further research is needed to confirm optimal dosing for antibacterial effects.
While the research on garlic’s antibacterial properties looks promising, more human studies are needed. Garlic should not replace conventional antibiotic treatment. But with your doctor’s approval, enjoying garlic in your diet and as a supplement may help prevent and fight some types of bacterial infections.
Frequently Asked Questions
What bacteria does garlic kill?
Based on laboratory research, garlic appears most effective against foodborne pathogens like Salmonella, E. coli, and S. aureus. Garlic may also inhibit Helicobacter pylori, dental plaque bacteria, and some antibiotic-resistant bacteria like MRSA.
Is garlic a natural antibiotic?
Garlic has shown antibacterial properties in lab studies, but human research is limited. At this time, there isn’t enough evidence to confirm garlic as a natural antibiotic. More studies are needed comparing garlic to conventional antibiotics.
How much garlic should you eat a day?
For general health, the recommended dietary allowance for garlic is about 4 grams (around 1 clove) per day. Higher intakes of 2-5 cloves per day seem safe for most healthy adults but may cause side effects like bad breath in some. For antibacterial effects, optimal dosing is unknown.
What are the side effects of garlic?
Common side effects from high garlic intake include odor, heartburn, gas, bloating, diarrhea, bleeding risk, and liver toxicity. Allergic reactions are possible but rare. To avoid adverse effects, start with small doses and speak to your doctor before increasing intake.
Does garlic boost immune system?
Some components of garlic may support immune health. However, the evidence is stronger for other immunity-boosting foods like citrus fruits, yogurt, and spinach. More research is needed to confirm if garlic significantly impacts immune function in humans.