Luckily for us, nature packaged the equivalent of a chemical factory inside every little garlic clove. In addition to potent sulfur compounds such as allicin, garlic has other secrets in its heart-disease-fighting arsenal.

Garlic's Attack on Plaque

Garlic contains several powerful antioxidants -- compounds that prevent oxidation, a harmful process in the body. One of them is selenium, a mineral that is a component of glutathione peroxidase, a powerful antioxidant that the body makes to defend itself. Glutathione peroxidase works with vitamin E to form a superantioxidant defense system.

Other antioxidants in garlic include vitamin C, which helps reduce the damage that LDL cholesterol can cause, and quercetin, a phytochemical. (Phytochemicals are chemical substances found in plants that may have health benefits for people.)

Garlic also has trace amounts of the mineral manganese, which is an important component of an antioxidant enzyme called superoxide dismutase.

In addition to its antioxidant powers, which keep the blood clean,
garlic can also slightly reduce blood pressure.

Oxidation is related to oxygen, a vital element to every aspect of our lives, so why is oxidation so harmful? Think about when rust accumulates on your car or garden tools and eventually destroys the metal. That rust is an example of oxidation.

Similarly, when your body breaks down glucose for energy, free radicals are produced. These free radicals start oxidizing -- and damaging -- cellular tissue. It's as if your bloodstream and blood vessels are "rusting out."

Antioxidants destroy free radicals, including those that are products of environmental factors, such as ultraviolet rays, air pollutants, cigarette smoke, rancid oils, and pesticides. The body keeps a steady supply of antioxidants ready to neutralize free radicals. Unfortunately, sometimes the number of free radicals can overwhelm the body's antioxidant stock, especially if we're not getting enough of the antioxidant nutrients.

When free radicals harm the cells that line your arteries, your body tries to mend the damage by producing a sticky spackle-like substance. However, this substance attracts cholesterol and debris that build up within the arteries, causing progressive plaque formation. The more plaque in your arteries, the more your health is in danger.

In addition, the cholesterol circulating through your arteries can be oxidized by free radicals. When LDL is oxidized, it damages the lining of the arteries, which significantly contributes to the buildup of plaque and the narrowing and hardening of the arteries.

Arteries, then, benefit greatly from the protection antioxidants provide. And garlic's ability to stop the oxidation of cholesterol may be one of the many ways it protects heart health.

Calcium: Friend
or Foe?Your body needs calcium for building and maintaining strong bones and teeth, helping your muscles work properly, reducing your risk of colon cancer, and many other functions. So calcium is definitely a friend. What you don't want calcium to do is get involved with plaque formation. But don't think that cutting back on calcium will lower the risk of this harmful process.

Your body determines how it uses calcium, and you can't do much about it. If you avoid calcium-rich foods, your body will make up for the deficit by drawing calcium out of its "savings account" -- your bones.

This can leave you with weakened bones that are more susceptible to breakage and eventually osteoporosis, a disease in which bones become very thin and break easily.

Consume about 1,000 milligrams of calcium each day (an eight-ounce glass of fat-free milk has 300 milligrams of calcium) to preserve your bone bank of calcium. Prevent calcium-fueled plaque buildup in your blood vessels not by avoiding calcium but by eating less saturated and trans fat and eating more antioxidant-rich foods, such as fruits, vegetables, and garlic.

Garlic also appears to help prevent calcium from binding with other substances that lodge themselves in plaque. In a UCLA Medical Center study, 19 people were given either a placebo or an aged garlic extract that contained S-allylcysteine, one of garlic's sulfur-rich compounds, for one year.

The placebo group had a significantly greater increase in their calcium score (22.2 percent) than the group that received the aged garlic extract (calcium score of 7.5 percent). The results of this small pilot study suggest that aged garlic extract may inhibit the rate of coronary artery calcification.

If further larger-scale studies confirm these results, garlic may prove to be a useful preventative tool for patients at high risk of future cardiovascular problems.

Easing the Pressure

Research suggests that garlic can help make small improvements in blood pressure by increasing the blood flow to the capillaries, which are the tiniest blood vessels. The chemicals in garlic achieve this by causing the capillary walls to open wider and reducing the ability of blood platelets to stick together and cause blockages.

Reductions are small -- 10 mmHg (millimeters of mercury, the unit of measurement for blood pressure) or less. This means if your blood pressure is 130 over 90 mmHg, garlic might help lower it to 120 over 80 mmHg. That's a slight improvement, but, along with some simple lifestyle adjustments, such as getting more exercise, garlic might help move your blood pressure out of the danger zone.

Preliminary studies indicate that garlic may also increase the production of nitric oxide. This chemical compound is produced in the lining of blood vessels, and it helps the vessels relax and allow blood to flow more freely.

Research published in August 2005 in the Proceedings of the National Academy of Sciences indicates that some of the sulfur-rich compounds in garlic help the blood vessels relax and enlarge, lowering blood pressure and improving blood flow throughout the body.

The Bottom Line: Garlic and Heart Health

Garlic seems to deserve a spot on the battlefield in the fight against heart disease. Even if its lipid-lowering abilities are less extensive than once thought, it appears that garlic's antioxidant ability helps protect arteries from plaque formation and eventual blockage. Because garlic also appears to increase the nitric oxide in vessels and lower your blood pressure, it becomes even more valuable.

Cholesterol and oxidation aren't the only bad guys that garlic keeps out of the body. On the next page you'll learn how nature's bouncer fights off viruses, as well.

A Guide To Heart-Disease Terms

With all this talk about heart disease, you might get confused by some of the terms we've used. Here's a handy glossary you can refer to:

Antioxidant: A substance that inhibits oxidation, a natural body process that causes cell damage. The body uses vitamins C and E as antioxidants. It also uses the minerals selenium and manganese to build potent antioxidant defense mechanisms, such as glutathione peroxidase and superoxide dismutase, to protect your cells.
Arteriosclerosis: A disease in which the arteries have thickened, hardened, and lost their elasticity, resulting in impaired blood flow. It develops in people who have high blood pressure, high cholesterol, diabetes, and other conditions or as the result of aging. It is also known as "hardening of the arteries."
Atherosclerosis: A type of arteriosclerosis characterized by plaque deposits on the interior walls of arteries.
Fibrinolysis: The body's natural process of breaking up blood clots.
Homocysteine: A sulfur-containing amino acid in the blood that has been linked to an increased risk of premature coronary artery disease, stroke, and blood clots in the veins.
Hypercholesterolemia: High levels of cholesterol in the blood.
Hyperlipidemia: High levels of lipids in the blood.
Lipids: Another word for fats. Includes all types of cholesterol and triglycerides.
Nitric oxide: In the human body, nitric oxide plays a role in oxygen transport, nerve transmission, and other functions. It also helps relax the lining of the blood vessels.
Oxidation: A chemical reaction between oxygen and another substance, sometimes resulting in damage to the substance. For instance, oxidized cholesterol damages the lining of arteries.

Want more information about garlic? Try:

Vegetable Recipes: Find delicious recipes that feature garlic.

Nutrition: Find out how garlic fits in with your overall nutrition plans.

Vegetable Gardens: Grow a full harvest of great vegetables this year.

Gardening: We answer your questions about all things that come from the garden.

This information is solely for informational purposes. IT IS NOT INTENDED TO PROVIDE MEDICAL ADVICE. Neither the Editors of Consumer Guide (R), Publications International, Ltd., the author nor publisher take responsibility for any possible consequences from any treatment, procedure, exercise, dietary modification, action or application of medication which results from reading or following the information contained in this information. The publication of this information does not constitute the practice of medicine, and this information does not replace the advice of your physician or other health care provider. Before undertaking any course of treatment, the reader must seek the advice of their physician or other health care provider.