About Garlic

Herb sold as a supplement in concentrated forms. Taken mostly for blood pressure and heart health.

Effectiveness Scores

Cardiovascular Health High blood pressure: 7.0/10.
Garlic helps your blood vessels relax by boosting nitric oxide, a gas your body uses to widen blood vessels. Wider vessels mean less pressure inside them. Aged garlic extract, a form of garlic soaked for months until its harsh compounds break down, is the type most studied for this.
Why this rating: In people with high blood pressure, garlic supplements lowered it by about 8 points on the top number and 5 on the bottom, taken daily for a few months. That's a meaningful drop. But in people whose blood pressure was already normal, garlic didn't change it at all, so it's not a way to prevent high blood pressure. Much of the positive research comes from a small group of researchers using one brand of aged garlic extract, and the studies were fairly small. It's a reasonable thing to try alongside your doctor's care and worth checking at home to see if it's working for you.
Good to know: garlic slows blood clotting slightly. If you take a blood thinner, talk to your doctor first.
Blood Sugar Support Type 2 diabetes: 7.0/10.
Garlic may help your body respond better to insulin, the hormone that moves sugar out of your blood and into your cells.
Why this rating: In people with type 2 diabetes, garlic lowered fasting blood sugar by about 7 points and A1c, a three-month average of blood sugar, by about two-thirds of a point. That's a useful amount on top of regular diabetes care. Most of the studies were small and short, and there's little evidence it does anything in people without diabetes. If you take diabetes medication, keep an eye on your numbers.
Lower Cholesterol High cholesterol: 6.0/10.
Garlic may slow down how much cholesterol your liver makes.
Why this rating: In people with high cholesterol, garlic lowered total and LDL cholesterol a little when taken for two months or more. But one of the best-designed trials, testing raw garlic and two popular supplements, found no effect on LDL at all. Results depend a lot on the type of garlic product, which is part of why studies disagree. It may help a little but don't count on it to bring high cholesterol down on its own.
Immune Support: 4.0/10 (moderate evidence).
Garlic seems to boost the activity of some immune cells, the ones that help fight off infections. In lab tests, it also kills some germs directly.
Why this rating: There's very little research on whether garlic actually helps you get sick less. One small trial found people taking garlic caught fewer colds, but it was low quality and hasn't been repeated. Another study found people taking aged garlic extract had milder colds, but not fewer of them. Garlic is safe to try during cold season, but there isn't enough evidence to expect much.

Understanding Effectiveness Scores

What does this mean?

Our effectiveness scoring system is based on scientific research and evidence. Each health outcome is rated on a scale of 1-10, with higher scores indicating stronger scientific support for the supplement's effectiveness.

1/10: Scientific evidence concludes that supplement is ineffective for purpose
2/10: No scientific evidence supports effectiveness
3/10: Inconclusive results regarding effectiveness
4/10: Minimal research on effectiveness
5/10: Limited evidence of effectiveness; may have potential benefits, but more research is needed
6/10: Some evidence supports the supplement's effectiveness, but research is mixed
7/10: Moderate evidence shows the supplement is effective for certain purposes, with limited population studies
8/10: Solid evidence suggests the supplement is effective, but research is not as extensive as higher levels
9/10: Strong scientific evidence supports the supplement's effectiveness, but some minor gaps in research remain (e.g., limited long-term studies or specific populations).
10/10: Ample scientific research demonstrates that the supplement is both highly effective and safe for long-term use.

Form Variations

Aged Extract
Garlic soaked for up to 20 months, which breaks down the harsh compounds and leaves a milder one called S-allylcysteine. Odorless and gentler on the stomach. This is what most of the blood pressure research used. Kyolic is the best-known brand.
Best for: blood pressure, people who can't stand the smell
Powder
Dried, powdered garlic. Its main active compound, allicin, only forms when garlic is crushed and exposed to water, so how much you actually get depends on how the product is made. Much of the older cholesterol research used garlic powder. Look for a label listing "allicin yield" or "allicin potential."
Best for: cholesterol, closer to fresh garlic
Enteric-coated Tablets
Garlic powder with a coating meant to protect it from stomach acid and cut down on garlic breath. Testing has found many of these tablets don't release their allicin properly, so the coating can end up working against you.
Best for: people who want garlic powder with less smell, from a brand with dissolution testing

Dosage & Timeline

Standard Dosages

Aged garlic extract: 600 to 1,200 mg
Garlic powder tablets: 600 to 900 mg

Timeline to See Results

Blood pressure: about 12 weeks
Cholesterol: about 2 months
Blood sugar: trials ran 8 to 24 weeks

All other outcomes may be noticed after extended use or lack enough studies to establish an effectiveness timeline.

Safety Information

Pregnancy and breastfeeding: Garlic in food is fine. Avoid supplement doses during pregnancy unless your doctor approves, since high doses may affect the uterus.
Blood-thinning effects: Garlic slows blood clotting slightly. Combined with warfarin, aspirin, or other blood thinners, it can raise your risk of bleeding. Talk to your doctor before taking garlic supplements if you use one.
Surgery: Because garlic slows clotting, stop garlic supplements at least 7 to 10 days before surgery.
Allergies: If you're allergic to onions, leeks, or chives, you may also be react to garlic.
HIV patients on saquinavir Garlic supplements can sharply lower the amount of some HIV medications in your blood, including saquinavir, which dropped by about half in one study. That can make the medication stop working. If you take HIV medication, don't take garlic supplements without your doctor's approval.

Side Effects

Common side effects:

Garlic breath and body odor from garlic's sulfur compounds. Aged garlic extract causes less of this.
Bloating, gas, or heartburn

Rare side effects:

Allergic reactions, like rash, itching, or swelling
Easier bleeding or bruising, since garlic slows blood clotting slightly. More likely if you also take a blood thinner.

Usage Information

Most people take garlic supplements for blood pressure and heart health. Others take it for cholesterol, blood sugar, or to try to avoid colds.

Garlic is a helper, not a treatment. It shouldn't replace blood pressure, cholesterol, or diabetes medication, and it can add to the effects of blood thinners.

User Experience

Gathered from reviews and forum posts, not from studies. What people report tells you what to expect. It does not tell you whether something works.

Most reviews focus on blood pressure and cholesterol, with many people reporting better numbers after a few months of regular use. Some say they get fewer or milder colds during cold and flu season. A few mention easier digestion.

The most common complaint is the smell. Many people prefer odorless forms, like aged garlic extract, over regular garlic powder.

Alternative Names

Allium sativum

Garlic