IN AUGUST 1993, fifty researchers gathered together in an overheated hotel conference room in Bethesda, Maryland, to design what would come to be known as the DASH study.
The initials “DASH” stand for Dietary Approaches to Stop Hypertension. The fifty researchers represented five research teams. There was Laura Svetkey, MD, and her team from Duke; George Bray, MD, and his team from the Pennington Center in Louisiana; Larry Appel, MD, and his team from Johns Hopkins; Bill Vollmer, PhD, and his team from Oregon Health Sciences Center; and my team from Harvard. The National Heart, Lung, and Blood Institute had selected these five teams from among forty applicants. Our task was to design an eating pattern that would lower blood pressure.
The teams had never worked together before. In fact, most of us did not even know one another. But it became clear from the very beginning that we were willing and eager to work together to design the “perfect” diet. By the end of that first meeting, we had agreed on a rough outline of the diets we would test and how we would test them. And I was honored that the group had selected me as the chairman of the overall study.
But it took another twelve months before we were ready to start testing the first research volunteer. That’s how long it took to design a study as complex and tightly controlled as the DASH study. DASH was a “feeding study”—that means we gave the research volunteers all of their food for the entire eleven weeks of the study. Volunteers were going to be studied simultaneously in North Carolina, Maryland, Louisiana, and Massachusetts. To be sure that the study was being conducted in the same way at all four sites and that the subjects at all sites were eating the same foods, we prepared careful menus and recipes that would be served in each location. We even worked with food companies that agreed to ship food items (such as bread, crackers, soup, and fruit) from the same production batch to all of our four sites so that the study volunteers were in fact eating identical foods. Samples of each recipe and meal were prepared, ground up, and chemically analyzed so that we were sure exactly what was in the foods. In addition, researchers at each site received identical training on how to measure blood pressure, how to weigh subjects, and how to measure body fat. We wanted to be absolutely sure that all four sites were feeding subjects the same food and measuring the effects of the diet in an identical way.
Once the study was designed, the four sites enrolled 459 volunteers in two and a half years. We tested three different diets. One third of the subjects ate a typical American diet. One third of the subjects ate a typical American diet enriched in fruits and vegetables. And the rest of the subjects received what is now called the DASH Diet. When the results were analyzed, the DASH Diet lowered systolic blood pressure by nearly 11 points—about as much as a typical antihypertensive medication and, in fact, far more than we researchers expected.
Since we first published these results in 1997 in the New England Journal of Medicine, many other studies have shown additional benefits of the DASH Diet. We know that it lowers blood pressure in people with high blood pressure, but we also now know that the DASH Diet reduces the development of hypertension, heart failure, heart attacks, and kidney stones, and even reduces the risk of developing colon cancer. Studies have shown that people who eat the DASH Diet “feel better.” One study even showed that the DASH Diet improves the ability to think clearly! And—most important for this book—the DASH Diet has also proven to be a very effective tool for those who want to lose weight.
So although DASH started off as a diet to lower blood pressure, with all this additional scientific evidence, the US Department of Agriculture now recommends the DASH Diet as the ideal eating pattern for all Americans. And a recent U.S. News & World Report ranking rated the DASH Diet as the “#1 Best Overall Diet” when compared to twenty other popular diets such as Weight Watchers, Jenny Craig, and South Beach.
But I often hear the comment, “It’s fine that the DASH Diet shows all those benefits when it’s tested in a study where volunteers are being given all of their food by the study staff. But how does the DASH Diet work in real life, when people need to select and prepare their own food?”
We’re happy to say that it works just fine. Dietitians and nutritionists routinely recommend the DASH Diet to people who are interested in improving their eating habits, who have specific medical conditions that would benefit from DASH, and who want to lose weight. People like the DASH Diet because it is easy to understand. It is about real foods, not special supplements or meals that you have to buy from a specific manufacturer. You can shop for the DASH Diet at the same stores where you’ve always shopped, and it allows you to follow either a meat-eater or vegetarian diet.
The DASH Diet started out as a tightly controlled scientific study but has turned into something much larger. Doctors, nutritionists, government agencies, and organizations such as the American Heart Association are recommending the DASH Diet. Now we want to get the 150 million Americans who would benefit from the DASH Diet to try it and stick with it.
We hope this book will be part of that solution.