Virtually all plants contain some chemicals that can help protect your health and some chemicals that can make you sick. So when you read or hear about a new chemical found in a plant, and that this chemical helps prevent or treat a disease, you should not go out and try to eat huge amounts of that one plant or buy an extract in pill form made from that plant. You should include a wide variety of plants in a healthy diet full of lots of fruits, vegetables, whole grains, beans, nuts and other seeds.

In 1844, Theodor Wertheim, a German chemist, distilled a pungent substance from garlic and called it allyl, the Latin name for garlic. Four years later Louis Pasteur in Paris showed that allyl could inhibit the growth of bacteria. This was a great discovery because 150 years ago, doctors had no antibiotics to kill bacteria, but at that time they also did not understand that bacteria cause many diseases. Garlic could have been the first penicillin, and Pasteur could have become extraordinarily rich.

One hundred years later in 1948, Arnold Stoll and Ewald Seebeck, researchers at Sandoz Company in Basel Switzerland showed that garlic does not smell offensively until the garlic bulb is crushed to form Allicin, the chemical that is responsible for the odor. The Sandoz researchers knew of Pasteur's studies 100 years before theirs, but they abandoned further research when the board of directors at Sandoz felt that nobody would take allicin, the extract from garlic, to treat infections because of its offensive odor.

Entrepreneurs now sell garlic pills claiming that they kill germs and have no smell. The research that I have found shows that if it doesn't smell, it isn't allicin and therefore it hasn't been shown to kill germs. Many studies show that allicin can kill bacteria in a test tube, but it cannot be used as a medicine because we don't know how it works in your body, how to make sure an extract contains the active chemicals, or how to make the proper dose. Enjoy garlic as a food and get its helpful properties as part of a varied diet that includes lots of different kinds of plants.

Gabe Mirkin, M.D.

Dr. Gabe Mirkin has been a radio talk show host for 25 years and practicing physician for more than 40 years; he is board certified in Sports Medicine and three other specialties.

Dr. Mirkin's daily features on fitness have been heard on CBS Radio News stations since the 1970's. He has written 16 books including The Sportsmedicine Book, the best-selling book on the subject that has been translated into many languages. His latest book is The Healthy Heart Miracle, published by HarperCollins.

Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. A Boston native, Dr. Mirkin did his residency at the Massachusetts General Hospital. He has served as a Teaching Fellow at Johns Hopkins Medical School, Assistant Professor at the University of Maryland, and Associate Clinical Professor in Pediatrics at the Georgetown University School of Medicine. He has run more than forty marathons and is now a serious tandem bicycle rider with his wife, nutritionist Diana Mirkin.