Quick answer (TL;DR): In trials, supplements made from it lowered blood pressure by a small amount (roughly 4/2 mmHg on average across a large 2025 meta-analysis of 108 trials) and cholesterol slightly. Evidence that it prevents colds is thin, and no food cures infections or "detoxes" the body. In cooking, a clove or two a day is typical and generally safe, but it is never a replacement for blood pressure or cholesterol medicine.
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What does the research on garlic actually show?
Most of the strongest studies tested supplements (powder, aged extract or oil), not the cloves you cook with. That matters when you compare their results with your own meals.
| Study | What was studied | Main finding |
|---|---|---|
| Nutrition Reviews, 2025 (Behrouz et al.) | Meta-analysis of 108 randomized trials of supplements in adults | Small average improvements in blood pressure (roughly 4/2 mmHg), cholesterol, blood sugar markers and inflammation, strongest in people with higher baseline risk |
| Frontiers in Nutrition, 2025 (Tang et al.) | Meta-analysis of 10 randomized trials in people with hypertension | Systolic pressure down about 4.2 mmHg and diastolic about 3.1 mmHg; the authors concluded the overall effect may be limited |
| Cochrane review, 2014 (Lissiman et al.) | Using it to prevent or treat the common cold | Only one small trial (146 people) qualified, so there was not enough evidence to say garlic works |
Does garlic lower blood pressure?
A little, mostly in people who already have high blood pressure. The 2025 Frontiers analysis found drops of about 4.2 mmHg (top number) and 3.1 mmHg (bottom number) in people with hypertension, and the authors described the overall effect as potentially limited. Older analyses of aged extract in hypertensive adults reported larger drops, around 8/5 mmHg, but newer pooled results are smaller.
For comparison, blood pressure medicines are prescribed because they reliably lower pressure by more than this. It should be seen as a small extra, not a treatment.
Does garlic lower cholesterol?
The large 2025 meta-analysis reported slightly lower total cholesterol (roughly 10 mg/dL) and LDL ("bad") cholesterol (roughly 6 mg/dL) with supplements. These are small changes. Statins and other prescribed treatments lower LDL far more, so it cannot stand in for them.
Can garlic help with blood sugar?
The same 2025 meta-analysis noted small reductions in fasting glucose and insulin resistance markers. The changes were modest, and they do not replace diabetes treatment. If you take diabetes medicine, talk to your doctor before starting supplements.
Does garlic prevent colds or cure infections?
Not proven. A Cochrane review found only one small trial of a supplement that met its standards. That trial reported fewer colds in the treated group, but the time to recover was similar, and the reviewers said more studies are needed. It is not a flu or infection cure, and it should not delay medical care for a serious infection.
It is also worth being clear that no food "detoxes" the body. Your liver and kidneys do that job.
What is allicin, and should you crush garlic?
Crushing or chopping raw cloves produces allicin, a sulfur compound that gives the bulb its smell and is behind much of the research interest. Heat reduces allicin. A common kitchen tip is to chop or crush the cloves and leave them for several minutes before cooking, which may preserve more of it. Cooked cloves are still a perfectly healthy part of a meal.
Is raw, cooked or supplement garlic better?
Trials have used raw cloves, powder, aged extract and oil, usually in concentrated doses. Results from those products do not automatically apply to the amount in a curry or dressing. If you want the possible benefits, eating it regularly in meals is a low-risk habit. Supplements need more care, as explained below.
How much garlic is OK to eat?
There is no official daily amount that I could verify. One to two cloves a day in food is typical in cooking and is generally well tolerated.
For more everyday ideas, see our nutrition tips and our post on eating more fruits and vegetables.
What are the side effects of garlic, and who should be careful?
- Common effects: bad breath, body odor, heartburn and stomach upset, especially in sensitive people or with raw cloves and high-dose supplements.
- Blood thinners or antiplatelet medicines (such as warfarin): some studies suggest high doses can affect clotting, although the evidence is mixed. Ask your doctor or pharmacist before taking these supplements.
- Blood pressure medicine: a supplement may add to the effect of your tablets, so check with your doctor first. Never stop or reduce prescribed medicine because of garlic.
- Before surgery: tell your doctor about any supplements you take.
- Pregnancy, breastfeeding, children, long-term conditions or regular medicines: food amounts are normal, but talk to a doctor first about supplements.
- Allergy: a skin rash or itching after handling or eating it is a reason to see a doctor. Get urgent medical help for swelling of the face or throat, or difficulty breathing.
Frequently Asked Questions
How much garlic should I eat per day for health benefits?
One to two cloves a day in food is typical and generally well tolerated. Clinical trials mostly used concentrated supplements, so food amounts should not be expected to match the results seen in trials.
Is raw garlic better than cooked garlic?
Crushing raw garlic produces allicin, the compound most often studied, and cooking reduces some of it. Cooked garlic is still nutritious. Letting crushed garlic rest for several minutes before cooking may preserve more allicin.
Can garlic replace my blood pressure medication?
No. The blood pressure effect of garlic is small, a few mmHg in most analyses, and it must never replace prescribed treatment. If you take medicine, talk to your doctor before adding garlic supplements.
Does garlic interact with any medications?
It can. Garlic supplements may affect clotting, so ask your doctor or pharmacist if you take warfarin or antiplatelet drugs. They may also add to the effect of blood pressure medicine.
Sources
- Behrouz et al., Nutrition Reviews, 2025: effects of garlic supplementation on cardiovascular risk factors in adults (systematic review and meta-analysis)
- Tang et al., Frontiers in Nutrition, 2025: long-term garlic consumption as an adjunctive treatment for hypertension
- Lissiman et al., Cochrane Database of Systematic Reviews, 2014: garlic for the common cold
- Ried, Experimental and Therapeutic Medicine, 2020: garlic and blood pressure in hypertensive adults (review and meta-analysis)
General information only, not medical, healthcare, or psychological advice. Check current medical guidelines with a certified physician or licensed healthcare provider before acting on anything published here. Never disregard professional medical advice or delay seeking it because of something you read on this site.
