Potatoes, breads, cereals, and other foods high in complex carbohydrates have always been regarded as cheap and essential - a staple for the poor. Now, however, as diets high in fats are being linked to heart disease and some cancers, as protein-rich meals are no longer the breakfast of champions, as high dietary fiber (found mostly in complex carbohydrates) is reported to possibly reduce the risk of colon cancer and heart disease, and as Americans learn that a 5-ounce steak has more calories than an equal amount of bread, pasta or potatoes (hold the butter), complex carbohydrates are becoming the chosen food of health-conscious diners in the 1990's.