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Moderate evidenceHeart & metabolic

Garlic Extract

Garlic reliably produces a small blood-pressure reduction in people who are actually hypertensive — roughly the effect of a low-dose drug in some trials — plus a modest cholesterol drop. Its reputation as a cold preventer rests on a single unreplicated trial.

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What the science says

  • Lowering blood pressure in hypertension Moderate evidence

    A 2020 review and meta-analysis of 12 trials in 553 hypertensive participants found aged garlic extract lowered systolic pressure by about 8.3 mmHg and diastolic by about 5.5 mmHg over 8-12 weeks — comparable to a standard first-line antihypertensive in these trials. Effects are much smaller or absent in people with normal blood pressure, so this is a population-specific result.

  • Cholesterol and lipids Moderate evidence

    An updated meta-analysis of 39 trials (2,300 participants) found garlic reduced total cholesterol by roughly 17 mg/dL and LDL by about 9 mg/dL in people with total cholesterol above 200 mg/dL treated for more than 2 months, with no meaningful effect on HDL or triglycerides. That is a real but clinically modest change — a fraction of what a statin delivers.

  • Preventing colds Limited evidence

    The claim rests almost entirely on one 146-person UK trial in which allicin-containing garlic cut cold episodes over 12 weeks. It has never been replicated, and Cochrane has repeatedly noted the evidence base for garlic and the common cold is a single trial of uncertain quality.

Dosage & safety

Studied doseAged garlic extract: 600-2,400 mg/day (typically 1.2 g/day) in divided doses, the form used in most blood-pressure trials. Garlic powder tablets: 600-900 mg/day standardized to about 1.3% alliin, delivering roughly 3.6-5.4 mg potential allicin. Raw garlic equivalents used in lipid trials are around 4 g/day (one to two cloves). Minimum 8-12 weeks for blood-pressure effects.
SafetyBreath and body odour are near-universal with allicin-yielding forms; aged garlic extract is largely odourless. GI upset, heartburn and, occasionally, allergic contact dermatitis occur. The clinically important issue is bleeding: garlic inhibits platelet aggregation, and case reports link it to spontaneous bleeding and to potentiation of warfarin — stop at least 7-10 days before surgery and use caution with warfarin, clopidogrel, aspirin and DOACs. Garlic induces CYP3A4 and P-glycoprotein and has been shown to significantly reduce saquinavir levels, so it is a real concern with protease inhibitors and other narrow-therapeutic-index drugs. It may add to antihypertensive and antidiabetic drug effects.

How to take it

TimingSplit it across the day; blood-pressure effects need 8-12 weeks to show.
With food?Take it with meals to reduce heartburn.
Worth knowingAged garlic extract is the largely odourless form used in most blood-pressure trials; allicin-yielding powders work differently and will make you smell of garlic.

Interactions

With medications

  • warfarin, clopidogrel, aspirin and DOACs

    Garlic inhibits platelet aggregation, and case reports link it to spontaneous bleeding and warfarin potentiation. tell your prescriber, and stop it 7-10 days before surgery

  • saquinavir and other HIV protease inhibitors

    Garlic induces CYP3A4 and P-glycoprotein and roughly halved saquinavir levels in a human study. do not combine

  • blood pressure medication

    Additive blood-pressure lowering, which is the intended effect but can overshoot. monitor your blood pressure when starting

  • antidiabetic medication

    Possible additive blood-glucose lowering. monitor your glucose when starting

With other supplements

  • fish oil, ginkgo and vitamin E

    Additive antiplatelet effect and bleeding risk. do not stack them around surgery

Well-established interactions only — this is not a complete list. Always tell your doctor and pharmacist what you take.

Frequently asked questions

Does garlic lower blood pressure?

In people with hypertension, yes, with moderate evidence: a meta-analysis of 12 trials found aged garlic extract lowered systolic pressure by about 8.3 mmHg and diastolic by about 5.5 mmHg over 8-12 weeks. Effects are much smaller or absent if your blood pressure is normal.

Does garlic lower cholesterol?

Modestly: a meta-analysis of 39 trials found garlic reduced total cholesterol by roughly 17 mg/dL and LDL by about 9 mg/dL in people with raised cholesterol treated for over 2 months. That is a fraction of what a statin delivers.

Does garlic prevent colds?

The evidence is limited: the claim that garlic prevents colds rests on a single 146-person trial that has never been replicated.

Is garlic extract safe with blood thinners?

Garlic inhibits platelets, and case reports link it to spontaneous bleeding and potentiation of warfarin, so tell your prescriber and stop garlic 7-10 days before surgery. Do not combine it with saquinavir or other HIV protease inhibitors, whose levels garlic lowers.

Scientific references

Where to buy

Kyolic, Aged Garlic Extract™, Cardiovascular Health, Original Formula 100, 300 Capsules (300 mg per Capsule)

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