WASHINGTON - Federal officials issued the eighth version of Dietary Guidelines for Americans on Thursday, altering some longstanding advice about what constitutes a nutritious meal and maintaining some food warnings despite strong debate over whether the alarm is scientifically justified.
Most notable among the changes, the government dropped its warning about avoiding cholesterol in the diet. Instituted in 1977, that caution helped sink egg sales across the country, but scientists now say the warning is unnecessary.
The new version of the influential advice book also eases up slightly on warnings about salty foods and omits a previous suggestion that Americans eat breakfast in order to stay fit. The old version of the dietary guidelines informed readers that "not eating breakfast has been associated with excess body weight," but the new version is silent on the topic.
The Dietary Guidelines for Americans, which are updated every five years, shape school lunches for millions of school children and serve as the basis of public health campaigns across the country aimed at reducing rates of heart disease, diabetes and cancer. The new version, however, was developed amid unusual scrutiny arising from questions about whether the recommendations have been based on sound science.
These questions led to a congressional hearing and in December, Congress approved a measure that calls for the National Academy of Medicine to review how the Department of Agriculture and the Department of Health and Human Services generate the advice book.
One of the key criticisms of the government effort is that it has generated advice that later has proven unfounded - with the decision to drop the dietary cholesterol warning offered as a prime example. But in talking to reporters on Wednesday, Health and Human Services Secretary Sylvia Burwell and Agriculture Secretary Tom Vilsack asserted that the government's advice, while changing with advances in science, has largely remained consistent over the years: consume more fruits, vegetables and whole grains; consume less saturated fat, sodium, and foods with added sugars, such as sweets and soft drinks.
"Americans will be familiar with the majority of our findings," Burwell said.
"There's been, obviously, a healthy debate about these guidelines," Vilsack said. "I think that has been extraordinarily helpful."
The controversies over the guidelines this year in many ways merely reflect the difficulties of nutrition science. Long-term experiments on human diets are rarely done, at least in part because it is difficult to control the diets of test subjects, and public health experts are left to rely on lesser forms of evidence. In assembling the guidelines, the government relies on the Dietary Guidelines Advisory Committee, a 15-member panel of experts.
In what may be its most controversial move, the new version of the dietary guidelines continues its longstanding warning about foods rich in saturated fats - that is, those fats characteristic of meat and dairy products. By doing so, the new guidelines will draw criticism, but any advice on saturated fats likely would have stirred opposition.
Leading groups of scientists and health organizations cannot agree on the dangers posed by saturated fats. On one side, groups such as the American Heart Association largely agree with the government warnings about saturated fats. In their view, consuming saturated fats leads to higher levels of "bad" cholesterol in the blood, and that, in turn, raises the risk of heart disease. Other groups, including the Academy of Nutrition and Dietetics, recommend that the dietary guidelines de-emphasize the potential dangers of saturated fats, suggesting instead that dietary guidelines warn of too many carbohydrates.
Given the divide among scientists, some experts have questioned whether the government ought to weigh in with a recommendation at all.
Christopher Gardner, a professor of medicine at Stanford, said the recommendation to limit saturated fats implies that scientists know for sure that they cause harm even though the issue is highly controversial.
"None of the research is definitive," Gardner said. "To really know what they do would take the kinds of studies we can't actually run in real life. But you can't have no advice, so this is the best advice from the data that is available and may not be very useful."
He said the focus on saturated fats arose in a decades ago when a compromise was struck during the development of the first set of dietary recommendations. The expert committee wanted to tell Americans to eat less meat but the meat industry lobbied against that measure. In the end, the dietary guidelines employed restrictions on saturated fats that in many ways served as a proxy for meat restrictions.
The new version of the dietary guidelines also introduces some new advice on two foods, coffee and salt, that have stirred disputes.
The guidelines tell people that drinking three to five cups of coffee per day - at eight ounces per cup - can be part of a healthy diet. The fact that some research suggests that coffee may be harmful for some people, depending on the speed with which they process caffeine, is not addressed by the guidelines or the expert committee that helped develop them. The guidelines stop short of encouraging people to take up the coffee habit.
The new version of the dietary guidelines also slightly softens the warning about salt. Under the old rules, most adults were advised to consume no more than 1,500 milligrams of sodium daily, while the limit for the others was 2,300 milligrams per day. Under the new guidelines, most adults are advised to limit themselves to 2,300 milligrams of sodium per day, or roughly the amount of sodium in a teaspoon of salt.
The federal officials who drew up the guidelines sought to focus attention less on the advice on any specific foods than on the overall healthy patterns that they are seeking to encourage.
Others critics have faulted the guidelines for failing to prevent the nation's epidemic of obesity.
"Given the same advice, it's not clear why we should expect different outcomes, especially when consumption data shows that over the past decades, Americans have, in fact, followed USDA advice," said Nina Teicholz, the author of "Big Fat Surprise" and a board member at the Nutrition Coalition, a new group, funded by Houston-based philanthropists Laura and John D. Arnold, lobbying for changes to the way the government develops dietary advice.