In what may be the most striking change, the new version drops the strict limit on dietary cholesterol, stepping back from one of most prominent public health messages since the ’60s.

But there were several other notable changes. Salt limits were eased, if only slightly, for many people. Coffee won official approval for the first time, with the book saying that as many as five eight-ounce cups a day is fine. And apparently, skipping breakfast is no longer considered a health hazard: While the old version of Dietary Guidelines informed readers that “not eating breakfast has been associated with excess body weight,” the new version is silent on the topic.

The Dietary Guidelines for Americans 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.

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This update of the Dietary Guidelines was conducted amid unusual scrutiny because of questions about whether the recommendations, issued since 1977, have been based on sound science.

These questions led to a Congressional hearing in October and Congress later 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 unnecessary or exaggerated — with the decision to drop the dietary cholesterol warning offered as a prime example by lawmakers and other critics.

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.

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“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.”

In what may be its most controversial move, the new version of the Dietary Guidelines continues the government’s longstanding warning about foods rich in saturated fats.

The issue of saturated fats — that is, those fats characteristic of meat and dairy products — is especially charged politically because it serves as a proxy for the arguments over the morality and health effects of meat consumption.

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An astonishing array of interests weigh in when the government sets standards that touch on meat consumption: comments come from the industry, from foodies, vegetarians, advocates of so-called “caveman diets” and animal rights activists, as well as from environmentalists concerned about the toll on natural resources exacted by raising livestock.

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The issue is further complicated because the science tracing health effects to meat consumption and saturated fats is unsettled.

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. 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.

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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.

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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.

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“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.”

Indeed, 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.

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In assembling the guidelines, the government relied on the Dietary Guidelines Advisory Committee, a 15-member panel of experts.

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Nevertheless, the new version seems inconsistent in places, or torn between new science and past recommendations.

For example, the new document dropped the warning about dietary cholesterol from its key recommendations and the document no longer calls for people to limit their cholesterol intake to 300 milligrams per day. This change was recommended by its own expert committee, which found that cholesterol is no longer “a nutrient of concern.”

But elsewhere in the report, the guidelines cite a 16-year-old report from the Institute of Medicine and advises people to “eat as little dietary cholesterol as possible while consuming a healthy eating pattern.”

Similarly, the report calls for people to limit the amount of saturated fat in their diet to 10 percent of their calories, and accordingly to choose milk and other dairy products that are no-fat or low-fat. But newer research, also cited by the guidelines, shows that merely reducing consumption of saturated fats may offer no benefit if people merely replace those saturated fats with carbohydrates, as they often do.

The publication of the new guidelines is destined to set off not just a barrage of arguments, but sales pitches. Indeed, it has already begun.

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“Mushrooms provide a simple solution to sodium and saturated fat reduction,” according to a press release about the Dietary Guidelines from the Mushroom Council, an industry group.

“According to the Guidelines, if consumed in moderation, alcohol ‘can help individuals achieve healthy eating patterns,’ according to a press release from the Distilled Spirits Council of the United States.

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. But the arguments tend to focus on specifics, and the new version of the Dietary Guidelines also introduces some new advice on two controversial foods.

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While the guidelines tell people that drinking three to five cups of coffee per day 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.

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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.

For all the debate, whether the guidelines have made American healthier is also a matter of debate. Critics have faulted the guidelines for failing to prevent the nation’s epidemic of obesity, and say major changes are necessary in the advice given.

“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.

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Staff Writer Ariana Eunjung Cha contributed to this report.