What is garlic’s effect on blood pressure?

Garlic (Allium sativum) is a vegetable that has been used as a natural blood-pressure-lowering remedy since ancient times. Recent research suggests this may be for good reason, as garlic appears to be a very effective remedy against high blood pressure. In fact, some studies report it to be as effective as standard blood-pressure-lowering medications — with much fewer side effects. One review of randomized controlled trials (RCT) — the gold standard in research — reported that garlic supplements may reduce systolic and diastolic blood pressure (the top and bottom numbers of a reading) by 6.7 and 4.8 mmHg, respectively, with no serious side effects. The studies included in the review provided participants with 188–2,400 mg of garlic powder supplements or aged garlic extracts per day and lasted 8–12 weeks. Several other recent reviews support these results, with many reporting blood pressure reductions ranging from 2.5–11.2 mm Hg following taking 600–2,400 mg of garlic powder per day for 8–24 weeks It’s noteworthy that although garlic’s blood-pressure-lowering effects appear universal, they seem greatest in people with elevated blood pressures, compared with those with blood pressures within the normal range. Garlic may help reduce systolic and diastolic blood pressure levels by up to 11.2 mm Hg. In some instances, garlic supplements may work as effectively as standard blood-pressure-lowering medications, with much fewer side effects.

How does it work?

Allicin, the main active compound in garlic, is thought to be largely responsible for garlic’s blood-pressure-lowering properties. Research suggests that allicin may prevent the production of angiotensin II, a compound responsible for increasing blood pressure by causing your blood vessels to tighten up or contract. By preventing the production of angiotensin II, allicin’s effects make it easier for your blood to flow freely, in turn, reducing your blood pressure. Allicin also appears to increase the production or availability of hydrogen sulfide and nitric oxide, two compounds crucial for regulating blood pressure levels. Moreover, experts believe that garlic’s anti-inflammatory and antioxidant properties may further contribute to garlic’s ability to reduce or prevent rises in blood pressure level. Garlic may help reduce blood pressure by preventing the production of angiotensin II, enhancing the availability of nitric oxide, or increasing the production of hydrogen sulfide. Its anti-inflammatory and antioxidant properties may further help.

Safety

Garlic has been used for over 5,000 years to prevent and treat disease, with few reports of side effects. To date, the majority of studies suggest that garlic supplements are very safe. The most commonly reported side effects include garlic breath, taste, or body odor. Stomach upset, gas, reflux, or abdominal pain are also somewhat common, but complaints generally remain minor. Other side effects may include hypersensitivity, headaches, dry mouth, coughs, hot flushes, mouth ulcers, and drowsiness, but these are considered rare. Side effects appear to be most common when eating large quantities of garlic, and less common when garlic powder supplements or aged garlic extracts are used. Large intakes of garlic, whether through diet or supplements, may thin the blood and increase the risk of bleeding when combined with anti-coagulant medication. If you’re currently taking medications, speak with your healthcare provider before drastically increasing your garlic intake. Garlic is generally considered safe. Side effects appear minor or rare and may be most likely to occur upon consuming raw garlic rather than aged garlic extracts or garlic powder supplements.

Effective dosages and forms

So far, most studies reporting blood-pressure-lowering effects have provided participants with the following forms and amounts of garlic.

• 188 mg of egg-yolk-containing garlic powder per day for 12 weeks
• 400 mg of raw garlic per day for 6 months
• 240–2,400 mg of aged garlic extracts per day for 2–23 weeks
• 600–2,400 mg of garlic powder per day for 8–24 weeks
• 12.3 mg of garlic oil per day for 16 weeks

Although blood pressure reductions have been observed with all of the forms above, some suggest that aged garlic extracts may be the most beneficial (6). In any case, speak with your healthcare provider before trying garlic as a blood-pressure-lowering remedy. They can help you figure out the best form and most effective dosage. Raw garlic, garlic powder, aged garlic extracts, or garlic oil all appear to help lower blood pressure. Effective dosages range from 12.3–2,400 mg per day for 2–24 weeks, depending on the form taken.

Other natural blood pressure remedies

In addition to garlic, other potentially effective natural blood-pressure-reducing remedies include:

• coenzyme Q10
• vitamin C
• long-chain omega-3s
• ginseng
• probiotics
• lipoic acid
• whole grains
• potassium
• vitamin E
• polyphenols
• vanadium

Keep in mind that although the use of many of these supplements to treat hypertension is supported by a large body of evidence, it’s always important to check with your doctor before adding any dietary supplement to your diet. Other natural blood-pressure-lowering remedies exist. That said, it’s always best to consult your doctor before adding any dietary supplement to your diet.

The bottom line

Garlic is a safe and effective natural blood-pressure-lowering remedy. It can be consumed in various forms, including raw garlic, garlic oil, aged garlic extracts, and garlic powder supplements. Relatively large doses are needed before effects are noticeable, but these remedies appear to be as effective as conventional blood pressure medications, with much fewer side effects. Therefore, using garlic as a natural blood-pressure-lowering remedy may be worth a try. Still, be sure to speak with your healthcare provider before adding a garlic supplement to your routine, especially if you’re taking medications or have an underlying health condition.