Does Garlic Lower Cholesterol?

Although more research is needed, there is evidence that garlic (Allium sativum) can help lower cholesterol. Garlic contains a bioactive compound called allicin that is thought to contribute to this effect.

The cholesterol-lowering effects add to the other reported benefits of garlic, including improved immunity, reduced blood pressure, and antioxidant properties.

This article takes an unbiased look at research investigating the use of garlic in lowering cholesterol. It also examines which form of garlic is "best" at bringing down cholesterol as well as the possible risks and side effects.

Garlic and High Cholesterol: Current Research

There have been numerous studies investigating the effects of garlic on blood cholesterol levels. While much of the evidence has been positive, the results remain far from consistent.

Allicin, a sulfur-based compound found in garlic, is attributed to the cholesterol-lowering effects. Even so, the exact mechanism of action remains under debate.

An older study from the Institute of Lipid and Atherosclerosis Research in Israel suggested that allicin blocks the production of the "bad" form of cholesterol—called low-density lipoprotein (LDL)—in the liver. It appears to do so by binding to proteins on liver cells called LDL receptors. By doing so, it may effectively "turn on" the production of LDL at the cellular level.

These findings were supported by a 2013 review of studies from the University of Adelaide in Australia in which the daily use of garlic was shown to reduce LDL and total cholesterol levels but had little to no impact on "good" high-density lipoprotein (HDL) cholesterol levels.

The investigators further reported that, of the 39 clinical trials included in the review, 26 showed significant reductions in LDL levels. The effects of garlic were largely dose-dependent, meaning that higher doses corresponded to greater drops in LDL. Moreover, the cholesterol-lowering effects tended to increase the longer that a person is on treatment.

Even so, the reductions in LDL levels (between 6% and 9%) were not enough to suggest that garlic alone can treat high cholesterol. The effects also do not appear to be lasting, with LDL levels returning to their baseline levels once treatment is stopped.

Not all of the studies in the review agreed with these findings. Thirteen of the 39 studies reported no significant changes in LDL or total cholesterol levels, while others reported that the cholesterol-lowering effects of garlic were only temporary. Further research is needed.

Which Form of Garlic Is Best for Cholesterol?

Garlic comes in many different forms: fresh, powders, oils, extracts, freeze-dried, and a variety of dietary supplements. There is currently no clear consensus as to which works best at lowering cholesterol and at what dose.

The 2013 review from the University of Adelaide suggested that garlic powder delivers the most consistent results, although the investigators did not include tablets or supplements in their review.

In 2020, researchers from the University of Vigo in Italy performed an allicin bioavailability study, analyzing how much allicin circulates in the bloodstream after consuming garlic in different forms. Of the 13 garlic supplements and nine garlic preparations (crushed, boiled, roasted, etc.), supplements overwhelmingly delivered the highest level of allicin into the bloodstream.

Although fresh crushed garlic achieved the highest spike overall, the effect was short-lasting, often dissipating within minutes.

Of the supplements, non-enteric-coated tablets performed best, delivering allicin at consistent blood levels for hours rather than minutes. Enteric-coated tablets performed nearly as well, although the bioavailability dropped significantly when taken with a high-protein meal. Garlic capsules performed similarly to enteric-coated tablets irrespective of food.

Dosage and How to Take

There are no guidelines for the appropriate use of garlic in any form. With that said, garlic poses few health risks and has been classified "Generally Recognized as Safe (GRAS)" by the U.S. Food and Drug Administration (FDA).

Most studies that examined the effectiveness of garlic in lowering cholesterol involved doses of between 500 to 1,000 milligrams (mg) per day. Raw garlic was generally prescribed as one to two cloves per day.

Garlic can be taken with or without food (although you may want to avoid taking enteric-coated garlic tablets with a high-protein meal as it may reduce its effectiveness).

As a general rule, never take more than the recommended dose on the product label. Moreover, opt for brands that have been independently tested by certifying bodies like the U.S. Pharmacopeia, ConsumerLab, or NSF International. This better helps ensure the supplements are untainted and safe.

Possible Side Effects

As with all drugs or supplements, garlic can cause side effects. Most are generally mild and tend to occur at higher doses.

The possible side effects of garlic supplementation include:

• Garlic-smelling breath
• Garlic-smelling body odor
• Flatulence/gas
• Heartburn
• Diarrhea

Similarly, garlic supplements should be stopped before scheduled surgery (including dental surgery) as they can potentially cause excessive bleeding.

Drug Interactions

There are certain risks associated with the use of garlic supplements, not least of which include drug interactions. For this reason, you should speak with your healthcare provider before starting treatment, especially if you are on chronic medications.

Some of the drugs garlic can possibly interact with include:

• Anticoagulants: Garlic can amplify the effects of blood thinners like warfarin, leading to easy bruising and bleeding.
• Antiretrovirals: Garlic can lower the blood concentration of HIV drugs called protease inhibitors and make them less effective.
• Cyclosporine: Garlic can reduce the effectiveness of this immunosuppressant drug commonly used to prevent organ transplant rejection and treat autoimmune diseases.
• Isoniazid: Garlic may reduce the effectiveness of this anti-tuberculosis drug.
• Nonsteroidal anti-inflammatory drugs (NSAIDs): Garlic may increase the risk of gastric bleeding with drugs like Advil (ibuprofen) and Aleve (naproxen).
  

Summary

A growing body of evidence suggests that garlic may help lower cholesterol, although the evidence is far from conclusive. Some studies suggest that the daily use of garlic may reduce "bad" LDL cholesterol by as much as 9%—a level that may help be useful in supporting standard treatments.

Other studies contend that garlic supplements are more effective in lowering cholesterol than fresh or prepared garlic. Further research is needed,

Although garlic is generally regarded as safe, speak with a healthcare provider before starting treatment to avoid drug interactions and other possible harms.

A Word From Verywell

Garlic is not an option if you are looking for a natural product to "replace" the medications prescribed by your healthcare provider. Nothing in the current research suggests that garlic is anywhere near as effective as statin drugs in treating high cholesterol.

As promising as some of the evidence may sound, self-treating a condition like high cholesterol is likely to cause more harm than good. It is important to remember that just because a product is "natural" does not mean that it is either safe or effective.

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