DASH simply stands for Dietary Approaches to Stop Hypertension. The Dash Diet is a book that uses a lot of fruits, vegetables, whole grains, fish, low-fat, and non-fat dairy, beans, and nuts to keep people at a low, healthy weight. By following this diet, one will decrease their hypertension, risk for stroke, and be at better odds of fighting off the onset of cancer.
Whereas I've never read this book before, it sounds to me like common knowledge. Obviously foods that are low in trans-fats, and with whole grains, protein, and vegetables is going to be healthier than eating deep fried foods, foods with high sugar content, and foods with a hefty carb count . Any diet that promotes vegetables, protein, whole grains, etc is going to reduce a person's risk for Hypertension.
I think there is a vast amount of resources available on what to eat and what not to eat to maintain a healthy lifestyle. You don't have to be a dietician to be able to know that vegetables, fruits, protein, nuts, and non-fat dairy is better for you than a big mac at McDonald's. I think the biggest problem in America is convenience and personal choice. People might know what to eat, they simply choose to eat for flavor and not for fueling the body. Then they can't seem to understand why they are getting sick all the time and feeling tired. It's like the old saying, "you are what you eat."
As for what dieting program is best, it all depends upon the person. Some people are disciplined enough to do something like weight watchers and count points. Others need a program like Jenny Craig or Nutria Systems that deliver all their daily meals to their house. With the Nutria Systems type programs, the foods calories are calculated and the person is given proper amount of calories from fat, carbohydrates, protein, vitamins, and minerals. These type of diets are better for the person that doesn't like to take the time to cook or worry about how healthy they are eating. All the healthy calculations are done by the company delivering the food so all the person has to do is eat and not worry about anything.