Conducted by researchers from the University of Minnesota, the study examined the diets of over 5,000 men and 6,000 women to determine whether they were eating according to American Heart Association (AHA) dietary guidelines.
Their findings, published in this month's issue of the Journal of the American Dietetic Association revealed that during the past 20 years study participants improved their diets by eating more fruit, vegetables, total grains and whole grains, as well as less saturated fat, trans fat, total fat, cholesterol and alcohol.
However, the researchers also found several continuing "areas of concern" in the study participants' diets over two decades: "unfavorable" salt intake and fish consumption, as well as a "continuous deterioration" in "energy balance" - consuming more calories than are burnt.
The dietary data, collected from people aged 25 to 74 who took part in the population-based Minnesota Heart Survey, revealed an overall improvement in compliance with the dietary recommendations developed to reduce heart disease risk between 1980-1982 and 2000-2002.
Improvements with respect to the fatty acid composition of the people's diets plateaued in 1995-1997, with intake of saturated fatty acids, trans-fatty acids, and cholesterol intake backsliding between 1995-1997 and 2000-2002, said the researchers.
Improvements in whole grain intake also appear to have leveled off between these survey periods despite a growing body of evidence for beneficial health effects of this dietary component, they added.
The findings suggest that public health efforts to improve Americans' diets for heart disease prevention may be yielding benefits, although the researchers cautioned that these efforts should also include a focus on moderating energy and sodium intake while encouraging increased consumption of fish.
The researchers also indicated that their findings could provide insight into trends in overall diet quality in relation to national dietary guidance for prevention of major chronic diseases, because of a nearly complete overlap between AHA guidelines and the government's guidelines.
"In comparing the Dietary Guidelines for Americans 2005 with the AHA dietary guidelines, only a few differences are apparent. Most notably, Dietary Guidelinesfor Americans 2005 includes recommendations related to added sugars and potassium that are not included or explicitly stated in the AHA dietary guidelines," wrote the researchers.