herb · for high blood pressure
Garlic
Helps blood vessels widen and relax, which lowers the pressure inside them.
Say that in clinical terms
S-allylcysteine promotes vasodilation, enhances nitric oxide production, and inhibits ACE.
How strong is the research?
3 papers read, 3 supporting.
Who was studied: Mostly people who already had high blood pressure. The effect is smaller if yours is normal.
How much to take
daily
600–1200 mg
Aged garlic extract preferred. Effects seen at 8-12 weeks. Average reduction 8-10 mmHg systolic.
Before you take it
- No NIH ODS Tolerable Upper Intake Level (UL) established for aged garlic extract as a preparation; most clinical trials use 600–1,200 mg/day without reported serious adverse events at these doses.
- Antiplatelet activity: may potentiate bleeding risk when combined with warfarin, aspirin, or clopidogrel — INR monitoring recommended.
- Significantly reduces plasma saquinavir (HIV protease inhibitor) levels — clinically important drug interaction; concurrent use should generally be avoided.
- Additive blood-pressure-lowering effect with antihypertensive medications; risk of clinically significant hypotension, particularly at higher doses or in susceptible individuals.
- Timing with antibiotics: take at least 2 hours before or 4–6 hours after tetracyclines or fluoroquinolones to avoid absorption interference (NIH ODS guidance; note asymmetry — 2h before vs 4–6h after).
- Common mild adverse effects include halitosis, heartburn, and GI discomfort; aged garlic extract is generally better tolerated for odor than raw garlic or allicin preparations.
What we make of it
Solid pooled evidence, though the main research group has manufacturer funding.
The detail
The pooled analysis is appropriate and the evidence is substantive. The research group behind several of the included trials has received funding from a garlic supplement manufacturer, which is worth weighing without dismissing the result.