Dear Dr. Mirkin:
How does drinking fruit juice increase risk for heart attacks?
Answer: The CARDIA study shows that all sugared drinks, including fruit juices, raise total cholesterol, the bad LDL cholesterol, triglycerides, and blood pressure (American Journal of Clinical Nutrition, August 13, 2010). People who drink fruit juice also have much larger waist circumferences. Abdominal obesity means that a person has high insulin levels and is at markedly increased risk for heart attacks and diabetes.
Taking sugar in drinks when you are not exercising increases risk for heart attacks, diabetes and premature death. Before food can pass from the stomach into the intestines, it must be converted to a liquid soup. No solid food passes into the intestines. When solid food enters your stomach, the pyloric sphincter at the end of the stomach closes and the stomach continuously squeezes the food until it is turned into a liquid soup. This can take up to four hours, which markedly delays the rise in blood sugar. Since fruit juice is already a liquid, it passes immediately into the bloodstream to cause a high rise in blood sugar.
Here’s how high rises in blood sugar cause heart disease: When blood sugar levels rise too high:
- your pancreas releases huge amounts of insulin which converts sugar to triglycerides (high triglycerides), which clog up your bloodstream to increase risk for clots, so you use up huge amounts of your good HDL cholesterol (low HDL cholesterol) in carrying triglycerides and your bad LDL cholesterol from your bloodstream into your liver.
- low HDL (good) cholesterol causes heart attacks because HDL is not available to carry cholesterol and triglycerides from your bloodstream.
- high insulin levels constrict arteries to cause heart attacks.
- high blood sugar levels cause sugar to stick to the surface membranes of cells to destroy them and cause all the horrible side effects of diabetes.
- high triglycerides in your liver cause a fatty liver that can lead to diabetes.
A practicing physician for more than 40 years and a radio talk show host for 25, Dr. Mirkin is a graduate of Harvard University and Baylor University College of Medicine. He is one of a very few doctors board-certified in four specialties: Sports Medicine, Allergy and Immunology, Pediatrics and Pediatric Immunology.
Dr. Mirkin's latest book is The Healthy Heart Miracle, published by HarperCollins. His daily short 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. Dr. Mirkin did his residency at the Massachusetts General Hospital and over the years 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.
Read more at www.drmirkin.com.
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