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Star Bulletin Alan Titchenal & Joannie Dobbs Health Options
Alan Titchenal
 & Joannie Dobbs
                  Monday, February 7, 2005


Drugs and diet can thin your blood

If you have a family history of heart disease or stroke, you probably know someone who takes some form of blood thinner. These drugs reduce the risk of a blood clot forming in a narrowed vessel and blocking blood flow to a part of the body. Some of these drugs have anti-platelet effects, and others function as anticoagulants.

Question: What are platelets?

Answer: Platelets are specialized disk-shaped cells in the blood that form clots to stop the bleeding when a blood vessel has been damaged. In a normal, healthy person, clot formation prevents excessive blood loss and can save your life.

But when vessels are injured by the effects of smoking, accumulation of cholesterol-rich plaques or chronic high blood pressure, platelets might "sense" blood-vessel damage and form a clot even though there is no risk of bleeding. If this clot blocks a vessel that supplies blood to the heart, it can cause a heart attack. If the vessel serves part of the brain, a stroke can occur.

Q: What is typically recommended to prevent excessive blood-clot formation?

A: Many physicians recommend a daily dose of aspirin for people at risk for heart disease or stroke. The prescribed dose can vary, so consult your physician before you start aspirin therapy. For specific types of risks, other anti-platelet drugs could be prescribed.

Those with especially high risk factors might need to take anticoagulant drugs such as coumadin (warfarin) that work by a different mechanism. Anticoagulant therapy requires frequent blood tests to make sure the dose is appropriate. A dose that is too high could cause excessive risk of bleeding. Strokes can be caused by blood-vessel blockage or by bleeding into the brain (hemorrhagic stroke), so too little or too much inhibition of blood clotting can be dangerous.

Q: Can dietary supplements affect blood clotting?

A: Yes. Many herbal supplements and teas can enhance or inhibit the effects of anti-clotting medications. Some commonly used supplements that can interfere with anti-clotting medications include alfalfa, angelica, bilberry, bromelain, chamomile, chlorella, coenzyme Q10, dong quai, evening primrose oil, feverfew, fish oils, ginkgo, ginseng, kelp/seaweed, saw palmetto, St. John's wort, willow bark and high doses of vitamins A, C, E and K.

Some herbs that are likely safe to use in cooking can interfere with anti-clotting medications when taken in concentrated amounts as pills and extracts. Examples include garlic, ginger and turmeric.

Also, some foods can affect blood thinning. Examples include grapefruit, green tea and green vegetables such as spinach. Green vegetables are generally rich sources of vitamin K, which can counteract the function of anticoagulant drugs.

Two additional basic but important factors also affect normal blood flow. Drinking enough fluid and consuming adequate protein are both important. Both, in turn, can help to prevent heart attacks and strokes.

Alan Titchenal, Ph.D., C.N.S. and Joannie Dobbs, Ph.D., C.N.S.
are nutritionists in the Department of Human Nutrition, Food and Animal Sciences,
College of Tropical Agriculture and Human Resources, UH-Manoa.
Dr. Dobbs also works with the University Health Service

© 2005 Honolulu Star-Bulletin --

Human Nutrition, Food & Animal Sciences · University of Hawai`i at Mānoa
1955 East-West Road · Honolulu, HI 96822
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