In order to assess whether consumers are getting contradictory or complementary advice on the foods they should eat, researchers from the US National Cancer Institute (NCI) looked at three of the main dietary guides in the US - the United States Department of Agriculture's MyPyramid, the National Heart, Lung and Blood Institute's DASH Eating Plan and Harvard's Healthy Eating Pyramid.
The NCI researchers compared recommendations and nutrient values within the three sets of guidelines, and found that while though the guides were derived from different types of nutrition research, they all shared consistent messages.
The findings are perhaps not surprising for nutritionalists, but they also send a message to manufacturers about ways to boost the healthy profile of their food products in line with consumer awareness about a healthy diet.
If consumers are hearing a consistent message about what they should and should not be eating, it follows that they will be more likely to select products that are in line with this.
"Recommendations are similar regarding almost all food groups for both types and amounts of foods people should eat," the researchers wrote in the March edition of the Journal of the American Dietetic Association.
"Primary differences were seen in the types of recommended vegetables and protein sources and the amount of recommended dairy products and total oil.
Overall nutrient values were also similar for most nutrients, except vitamin A, vitamin E and calcium."
The researchers suggested that their analysis showed that the three sets of guidelines were in many ways 'future proof'.
"The evidence base for optimal diets continues to evolve," they said.
"However, inherent in these guides is a pattern of eating that focuses on nutrient-rich foods and limited calories from added sugar and solid fat," suggesting that no matter whether daily intake figures change, the basic advice would remain sound.
However the NCI research contrasts with that of scientists from the Albert Einstein College of Medicine of Yeshiva University in New York, who also looked at the range of dietary guidelines.
In their study, published in the January 22 online edition of the American Journal of Preventive Medicine, the Einstein researchers raised questions about the benefits of federal dietary guidelines, and suggested that guideline writers should be guided by explicit standards of evidence to ensure the public good.
"When dietary guidelines were initially introduced in the late 1970s, their population-based approach was especially attractive since it was presumed to carry little risk," said Paul Marantz, associate dean for clinical research education at Einstein.
"However, the message delivered by these guidelines might actually have had a negative impact on health, including our current obesity epidemic.
The possibility that these dietary guidelines might actually be endangering health is at the core of our concern about the way guidelines are currently developed and issued."
New dietary guidelines are due to be drafted by the USDA in 2010, and the team led by Marantz said it was vital to ensure that mistakes that had been made in the past were not repeated.
"In 2000, the Dietary Guideline Advisory Committee suggested that the recommendation to lower fat, advised in the 1995 guidelines, had perhaps been ill-advised and might actually have some potential harm," the study notes.
"The committee noted concern that the previous priority given to a 'low-fat intake' may lead people to believe that, as long as fat intake is low, the diet will be entirely healthful.
This belief could engender an overconsumption of total calories in the form of carbohydrates, resulting in the adverse metabolic consequences of high-carbohydrate diets."
The committee also noted that "an increasing prevalence of obesity in the United States has corresponded roughly with an absolute increase in carbohydrate consumption," the researchers said.
Although the Einstein study is careful not to make direct links between poorly worded dietary guidelines and the increase in food-related diseases, Marantz and his colleagues said that it nonetheless "raises the possibility of a net harmful effect of seemingly innocuous dietary advice.
These dietary recommendations did not necessarily cause harm, but there is a realistic possibility that they may have."