NEW YORK (Reuters Health) - Over the past 20 years, the diets of American adults have become more consistent with most dietary recommendations for heart disease prevention -- but the trend may not be continuing, research suggests.

Between 1980 and 2002, Americans ate more fruit and vegetables, total grain and whole grain, and less total fat, saturated fat and trans fats, and cholesterol. They also drank less alcohol, researchers report in the Journal of the American Dietetic Association.

The improvements in diet paralleled declining rates of heart disease and death, "suggesting that public health efforts to improve the population diet for coronary heart disease prevention may be yielding health benefits," they say.

The observations stem from an analysis of dietary data collected as part of the Minnesota Heart Survey, an ongoing study examining trends in risk factors for heart disease among adults living in the Minneapolis-St. Paul metropolitan area.

However, in contrast to the improvements mentioned, Dr. Lisa Harnack of the University of Minnesota in Minneapolis and colleagues noted little improvement -- or trends in the wrong direction-- for three areas: energy balance (taking in more calories than is expended) worsened, as did sodium intake, while the amount of fish consumed remained below recommended levels.

Another "worrisome finding from our study," Harnack told Reuters Health, "is that overall improvement in the diet appear to have plateaued and leveled off during the last 5 years period we studied, after consistent progress between 1980-82 and 1995-97."

"Indeed, reversal of some favorable trends was observed with saturated fat and cholesterol increasing in the latest survey period. The rising popularity of low-carbohydrate diets such as the Atkins diet may have contributed to these unfavorable trends," she said.

Stepped up efforts to get more Americans to adopt heart-healthy diets are needed, Harnack concluded. These efforts "include a focus on reducing energy intake and/or increasing physical activity level; limiting salt intake; and increasing fish consumption. Also, intake of foods high in saturated fat, trans fat, and cholesterol should be limited," she said.