Garlic (Allium sativum) has been eaten and used traditionally for thousands of years.
It belongs to the same plant family as foods such as:
- onions,
- leeks,
- shallots,
- and chives.
Today, garlic is used worldwide to flavour everything from soups and stews to sauces, vegetables, meat, fish and rice dishes.
Garlic is also widely promoted as a natural remedy for conditions ranging from high blood pressure and high cholesterol to infections and the common cold.
But many popular garlic claims go considerably further than the scientific evidence.
So what does research actually tell us?
What Makes Garlic Different?
Garlic contains a variety of sulfur-containing compounds.
One of the best known is allicin.
Interestingly, an intact garlic clove contains very little allicin.
When garlic is:
- chopped,
- crushed,
- cut,
- or chewed,
an enzyme called alliinase helps convert another compound, alliin, into allicin.
Allicin itself is unstable and quickly changes into other sulfur-containing compounds.
These compounds are among the reasons researchers have been interested in garlic's possible biological effects.
However, demonstrating an effect in a laboratory does not automatically prove that eating garlic will prevent or treat a disease in humans.
That distinction is important when evaluating garlic's health claims.
Is Garlic Nutritious?
Yes.
Garlic contains small amounts of several nutrients, but a normal serving is quite small.
Garlic can contribute nutrients and plant compounds to the diet, but it should not be considered a major source of every vitamin or mineral.
Its greatest everyday advantage may simply be that it adds considerable flavour to food without requiring much:
- salt,
- sugar,
- or saturated fat.
That can make garlic useful when preparing nutritious meals.
Garlic and Cholesterol
This is one of the better-studied areas of garlic research.
According to the U.S. National Center for Complementary and Integrative Health (NCCIH), garlic supplements may modestly reduce total cholesterol and LDL cholesterol in people with high cholesterol.
LDL is sometimes called “bad” cholesterol because high levels can contribute to plaque formation in arteries.
However, there are important limitations.
The cholesterol-lowering effect of garlic supplements is modest compared with cholesterol-lowering medicines.
Garlic therefore should not be used as a substitute for prescribed cholesterol medication.
People with high cholesterol should continue following professional advice regarding:
- diet,
- physical activity,
- weight management,
- smoking,
- medicines,
- and other cardiovascular risk factors.
Can Garlic Lower Blood Pressure?
Possibly, but the evidence needs to be interpreted cautiously.
Some research suggests that certain garlic preparations may produce a small reduction in blood pressure among people with hypertension.
However, NCCIH notes that much of the research consists of small, preliminary or lower-quality studies.
No dietary supplement has been shown to lower blood pressure as effectively or reliably as established antihypertensive medicines.
Therefore:
Do not replace blood-pressure medicine with garlic.
And there is no established evidence that eating one raw garlic clove on an empty stomach is a reliable treatment for hypertension.
If you have high blood pressure, continue the treatment plan recommended by your healthcare professional.
Does Garlic Prevent Heart Disease?
This claim is often exaggerated.
Because garlic supplements have been studied for effects on cholesterol and blood pressure, it is tempting to conclude that they automatically prevent heart attacks and cardiovascular disease.
That conclusion has not been established.
NCCIH states that there is no evidence that garlic supplements prevent heart disease.
There is a major difference between slightly changing a cardiovascular risk factor and proving that a product prevents heart attacks, strokes or cardiovascular deaths.
Garlic can certainly be included in a heart-healthy diet, but it should not be marketed as heart-disease medication.
Garlic and Blood Sugar
Some studies have investigated garlic supplementation in people with diabetes.
NCCIH reports that garlic supplements may reduce blood glucose to a small extent in people with diabetes.
That does not make garlic a treatment for diabetes.
People with diabetes should not reduce or discontinue:
- insulin,
- metformin,
- other diabetes medicines,
- blood-glucose monitoring,
- or professional medical care
because they are consuming garlic.
If you use concentrated garlic supplements alongside diabetes medicines, discuss this with a healthcare professional.
Does Garlic Strengthen the Immune System?
Garlic supplements are frequently promoted as “immune boosters.”
The evidence is much weaker than the advertising suggests.
NCCIH reports that very little research has investigated garlic supplements for immune enhancement, and the available studies are limited.
The immune system is extremely complex.
Its normal function depends on many factors, including:
- adequate nutrition,
- sleep,
- vaccination,
- physical activity,
- age,
- medical conditions,
- and exposure to pathogens.
Garlic can be part of a nutritious diet, but it should not be treated as an immune-system medicine.
Can Garlic Prevent or Cure a Cold?
Evidence is insufficient.
A limited number of studies have examined garlic supplements for the common cold.
NCCIH's review of the evidence concludes that there is insufficient clinical-trial evidence to determine whether garlic prevents or treats the common cold.
So adding garlic to soup when you have a cold is perfectly reasonable if you enjoy it.
But garlic has not been proven to cure:
- colds,
- influenza,
- nasal congestion,
- sore throat,
- or cough.
Most uncomplicated colds improve with time and supportive care.
Does Garlic Fight Bacteria and Fungi?
Garlic compounds have demonstrated antimicrobial activity in laboratory research.
But laboratory findings do not mean that raw garlic should be applied directly to infections or used instead of antimicrobial medicines.
Bacterial and fungal infections can require specific diagnosis and treatment.
Eating garlic is not equivalent to receiving:
- an antibiotic,
- an antifungal medicine,
- an antiviral medicine,
- or an antiparasitic treatment.
This distinction is particularly important because delaying appropriate treatment can allow some infections to worsen.
Never Put Raw Garlic on a Skin Infection
The old version of this article recommended applying crushed raw garlic directly to infected skin.
Do not follow that advice.
Fresh raw garlic applied to skin can cause:
- severe irritation,
- redness,
- blistering,
- and chemical burns.
NCCIH specifically warns about this risk.
If you have an infected wound or persistent skin problem, obtain appropriate medical advice rather than applying crushed garlic.
Don't Put Raw Garlic on a Toothache Either
Another old home remedy involves placing crushed garlic directly against a painful tooth or gum.
That is not a safe substitute for dental care.
Raw garlic can irritate or burn oral tissues.
A toothache may be caused by:
- tooth decay,
- an abscess,
- a cracked tooth,
- gum disease,
- infection,
- or another dental condition.
Pain relief does not address the underlying cause.
Persistent or severe tooth pain requires dental assessment.
Facial swelling, difficulty swallowing, difficulty breathing or rapidly worsening symptoms require urgent medical attention.
Can Garlic Treat Vaginal Infections?
Garlic should not be inserted into the vagina to treat yeast infections, bacterial vaginosis or sexually transmitted infections.
Different vaginal infections require different treatments.
Symptoms such as:
- unusual discharge,
- itching,
- burning,
- unpleasant odour,
- pelvic pain,
- sores,
- or pain during urination
can have many possible causes.
Using garlic can cause irritation and may delay correct diagnosis.
Seek appropriate healthcare advice instead.
Does Garlic Prevent Cancer?
There is no good basis for saying garlic prevents cancer.
Garlic and other Allium vegetables have been studied for possible relationships with cancer risk.
However, current evidence does not establish garlic as a cancer-prevention treatment.
NCCIH reports that consuming garlic does not appear to reduce stomach-cancer risk, while its effect on colorectal-cancer risk remains uncertain.
Garlic supplements should not be used as a cancer-prevention strategy.
More importantly, garlic must never replace:
- cancer screening,
- vaccination where applicable,
- tobacco avoidance,
- healthy weight management,
- medical assessment,
- or cancer treatment.
Garlic Is Not a “Detox”
Claims that garlic activates the liver and removes toxins from the body are popular online.
“Detox” language often oversimplifies normal human physiology.
Your body already has sophisticated systems for processing and eliminating waste products, involving organs including the:
- liver,
- kidneys,
- lungs,
- digestive system,
- and skin.
Garlic can be part of a healthy diet, but there is no need to consume garlic specifically to “clean” or “detoxify” your liver.
Does Garlic Treat Hyperthyroidism?
No established medical evidence supports garlic as an effective treatment for hyperthyroidism.
Hyperthyroidism means the thyroid gland produces excessive thyroid hormones.
Depending on the cause and circumstances, treatment may involve:
- antithyroid medicines,
- radioactive iodine,
- surgery,
- medicines to control symptoms,
- or other medical management.
Untreated hyperthyroidism can cause serious complications.
Do not replace thyroid treatment with garlic.
Can Garlic Cure Scurvy?
Scurvy results from severe vitamin C deficiency.
Garlic is not an appropriate treatment strategy for scurvy.
Vitamin C-rich foods include:
- citrus fruits,
- peppers,
- kiwi,
- strawberries,
- broccoli,
- and several other fruits and vegetables.
Someone suspected of having scurvy requires appropriate medical assessment and correction of the deficiency.
Garlic and Bone Health
The old article claimed that approximately two grams of garlic could reduce estrogen deficiency and benefit women's bones.
That claim is far too specific for the available evidence.
Researchers have explored possible relationships between garlic compounds and bone health, but there is insufficient evidence to recommend garlic as a treatment for:
- osteoporosis,
- osteoarthritis,
- estrogen deficiency,
- or fractures.
Established approaches to bone health include appropriate:
- calcium intake,
- vitamin D,
- weight-bearing activity,
- avoidance of smoking,
- and medical treatment when clinically indicated.
Garlic and Pregnancy
Garlic used in the ordinary amounts found in food is generally different from consuming concentrated garlic supplements.
NCCIH notes that garlic may not be safe during pregnancy or breastfeeding when taken orally in amounts greater than those normally found in foods, because adequate safety information is lacking.
There is also insufficient evidence to recommend garlic supplements to increase fetal weight.
Pregnant people should discuss herbal or concentrated supplements with an appropriate healthcare professional.
Does Garlic Help With Weight Loss?
Garlic is sometimes marketed as a weight-loss food or supplement.
There is no convincing basis for treating garlic as a stand-alone weight-loss method.
Body weight is influenced by many factors, including:
- overall energy intake,
- physical activity,
- sleep,
- medicines,
- hormones,
- medical conditions,
- genetics,
- and the overall dietary pattern.
Garlic can make nutritious meals flavourful, but eating garlic does not bypass these factors.
Does Garlic Repel Mosquitoes?
Eating garlic should not be relied upon as protection from mosquitoes.
In areas where mosquitoes transmit diseases such as:
- malaria,
- dengue,
- yellow fever,
- chikungunya,
- or Zika,
use evidence-based mosquito protection recommended by local public-health authorities.
Depending on the location, this can include:
- approved insect repellents,
- mosquito nets,
- window screens,
- protective clothing,
- and mosquito-control measures.
Garlic is not a substitute.
Can Garlic Treat Warts?
Garlic is sometimes promoted as a home remedy for warts.
However, applying raw garlic to the skin carries a risk of irritation and chemical burns.
Warts often disappear eventually without treatment, but various established treatments are available.
A healthcare professional can assess lesions that:
- bleed,
- change appearance,
- hurt,
- spread rapidly,
- occur in sensitive locations,
- or are uncertain in diagnosis.
Does Garlic Kill Intestinal Worms?
Garlic should not replace proven treatment for parasitic infections.
Different intestinal parasites require different approaches.
If you suspect worms—particularly in a child—seek appropriate healthcare or pharmacy advice according to local guidance.
Using garlic instead of effective treatment may allow the infection to continue.
What About Earache?
Do not insert raw garlic, garlic cloves, homemade garlic oil or other unapproved preparations into the ear.
Ear pain can result from:
- infection,
- earwax,
- injury,
- pressure changes,
- a perforated eardrum,
- or pain referred from teeth or the jaw.
Treatment depends on the cause.
Seek professional advice for persistent, severe or recurrent ear pain.
Raw Garlic vs Cooked Garlic
Both can be included in a healthy diet.
Crushing or chopping garlic initiates chemical reactions that produce allicin and related compounds.
Cooking changes some of these compounds.
That does not mean raw garlic is automatically healthier in every situation.
Raw garlic is also more likely to cause:
- heartburn,
- stomach discomfort,
- nausea,
- and strong breath.
The best approach is to use garlic in whatever food-safe preparation you enjoy and tolerate.
Is There an Ideal Number of Garlic Cloves Per Day?
No universally established medical recommendation says everyone should consume a specific number of garlic cloves each day.
The old advice to consume one clove two or three times every day should therefore be removed.
The amount used in cooking varies widely between cultures and individuals.
Garlic used as food can simply be incorporated according to taste.
Concentrated garlic supplements are a different matter because their composition and doses vary.
Garlic Supplements Are Not the Same as Garlic in Food
Garlic supplements are sold in several forms, including:
- garlic powder,
- garlic oil,
- aged garlic extract,
- tablets,
- and capsules.
Products can differ substantially in:
- composition,
- preparation,
- active compounds,
- dosage,
- and quality.
Therefore, research involving one garlic preparation does not necessarily apply to every product sold as “garlic.”
And a supplement should not automatically be assumed safer because it is labelled natural.
Garlic and Bleeding Risk
This is one of the most important safety issues.
Garlic supplements may increase the risk of bleeding.
Extra caution is particularly important for people who:
- take anticoagulants or other medicines affecting bleeding,
- take aspirin,
- have a bleeding disorder,
- or are preparing for surgery.
Tell your healthcare professionals about all supplements you use.
Do not assume they already know.
Garlic Can Interact With Medicines
Herbal products can interact with medicines.
NCCIH notes, for example, that garlic has been found to interfere with the effectiveness of saquinavir, a medicine used in HIV treatment.
Other interactions may also be relevant depending on the product, dose and medicines being taken.
If you regularly take prescription medicines and want to begin a concentrated garlic supplement, discuss it with a healthcare professional or pharmacist first.
Possible Side Effects of Garlic
Garlic consumed as food is generally well tolerated by most people.
Possible effects include:
- garlic breath,
- body odour,
- heartburn,
- abdominal discomfort,
- gas,
- nausea,
- and allergic reactions.
Raw garlic may produce more gastrointestinal symptoms in some people.
Garlic supplements can have additional safety considerations, including bleeding risk and drug interactions.
Is Black Garlic Healthier?
Black garlic is ordinary garlic that has undergone controlled heating and ageing, which changes its:
- colour,
- flavour,
- texture,
- and chemical composition.
It has become popular as a specialty food and is often marketed with extensive health claims.
Although research is investigating black garlic, there is not enough evidence to say that it cures or prevents major diseases.
It can be enjoyed as another food ingredient if you like its sweeter, milder flavour.
Easy Ways to Use Garlic in a Healthy Diet
Garlic can make nutritious foods more flavourful.
Try it:
- crushed into tomato-based sauces,
- roasted with vegetables,
- cooked with beans or lentils,
- added to soups and stews,
- mixed into marinades,
- cooked with fish or poultry,
- added to stir-fries,
- combined with herbs and olive oil,
- or incorporated into traditional dishes.
Using herbs, spices, onions and garlic for flavour may also help some people rely less heavily on salt.
Food Is Not Medicine Simply Because It Has Health Benefits
This distinction matters throughout nutrition.
Garlic contains biologically active compounds and may have modest effects on some health measurements.
That does not make it equivalent to a medicine.
A food can be:
- nutritious,
- useful,
- enjoyable,
- and part of a healthy dietary pattern
without curing diseases.
Exaggerating garlic's benefits can actually make good nutrition information less trustworthy.
The Bottom Line
Garlic is a flavourful and useful ingredient that fits comfortably into a healthy diet.
Research suggests that some garlic supplements may have modest effects on cholesterol and possibly blood pressure, but the evidence does not support many of the dramatic claims commonly made about garlic.
Garlic has not been established as a treatment for cancer, thyroid disease, vaginal infections, toothache, skin infections, worms, colds, warts or other medical conditions.
Never apply raw garlic directly to skin because it can cause serious irritation and chemical burns.
Garlic supplements also deserve more caution than ordinary culinary garlic because they may increase bleeding risk and interact with medicines.
Enjoy garlic as food—but don't expect it to replace evidence-based healthcare.
Medical Disclaimer
This article provides general nutrition and health information for an international audience. It is not a substitute for diagnosis, treatment or individualized medical advice. People taking prescription medicines, those with bleeding disorders, people preparing for surgery, and those who are pregnant or breastfeeding should seek professional advice before using concentrated garlic supplements.
Sources and Further Reading
National Center for Complementary and Integrative Health — Garlic: Usefulness and Safety
https://www.nccih.nih.gov/health/garlic
National Center for Complementary and Integrative Health — High Cholesterol and Natural Products
https://www.nccih.nih.gov/health/providers/digest/high-cholesterol-and-natural-products
National Center for Complementary and Integrative Health — Complementary Health Approaches for Hypertension
https://www.nccih.nih.gov/health/providers/digest/complementary-health-approaches-for-hypertension
National Center for Complementary and Integrative Health — The Common Cold and Complementary Health Approaches
https://www.nccih.nih.gov/health/providers/digest/the-common-cold-and-complementary-health-approaches-science
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