Last week, a group of respected epidemiologists called for a rethinking of the Dietary Guidelines for Americans, the nutrition advice to the public and the standard for all federally subsidized meals from school lunches to military rations.
The guidelines, argued researchers from New York's Albert Einstein College of Medicine and Yeshiva University, may have inadvertently fueled America's rising tide of obesity and caused more harm than good.
Instead of dictating specific serving sizes from different food categories, said Dr. Paul Marantz, of Albert Einstein, the guidelines should lay out the evidence - explaining its strengths and weaknesses - and let people make their own choices.
"The notion that the government should tell people what and how much to eat is inherently paternalistic," Marantz and colleagues wrote in an essay in the Jan. 22 online edition of the American Journal of Preventive Medicine.
Too often, Marantz and his colleagues said, the guidelines have promoted nutritional advice that is not supported by research. Take salt for example: the current suggested limit is 2,300 mg a day.
But Marantz said that number is "picked out of the air."
So, should the government be dispensing advice if the information isn't rock solid? Some say there isn't a choice.
"The evidence is never completely in," said Marion Nestle, a professor in the Department of Nutrition, Food Studies, and Public Health at New York University. "But just because the science isn't complete doesn't mean you shouldn't give the public the best advice based on the best information you have."
Unfortunately, federal advice on nutrition has not had as strong a track record.
From 1980 to 2000, the guidelines advised people to get less than 30 percent of their calories from fat, both to reduce the risk for heart disease and keep obesity at bay. But few succeeded at lowering their fat intake, and instead began eating an average of more than 300 extra calories a day - in part, because of the proliferation of non-fat, high-calorie snack foods that met the guideline.
"With the low-fat message, there was an unintended consequence," said Alice Lichtenstein, a heart disease researcher at the USDA's Human Nutrition Research Center on the Tufts medical campus who served on the committee that wrote the federal guidelines in 2000. "A mutation of the message" made it seem as though "low-fat was equivalent to low-calorie."
Dietary guidelines were revised in 2000 to encourage people to reduce their consumption of saturated fat - from foods such as hamburgers and whole milk - rather than their overall fat intake.
Marantz concedes that the latest set of guidelines, from 2005, are an improvement.
"There's a lot of good information there," he said, which leaves people with more information to make their own decisions about whether to make a dietary change. "I should be appropriately respectful of that improvement."
But he and his co-authors think more revisions are needed before the next set of guidelines is released in 2010. They say there's still too much specificity in the suggested number of daily servings of fruits and vegetables and ounces of meat, among other things, that is not backed by rigorous science.
