The federal government's influential Dietary Guidelines for Americans, which were released Thursday, are updated every five years, and the debate over saturated fats, red meat, caffeine and salt was especially intense this time around.
The guidelines are the basis of everything from school lunch programs to the diets promoted in bestselling books, but in recent years some scientists have begun to question the one-size-fits-all approach. A growing body of research supports the theory that a person's genetic makeup or microbiome (the organisms that live on or inside of you and help to make you who you are) plays a key role in how food affects the body — and that the impact can be different from one individual to another. That work supports a more personalized approach to diet, which some researchers have argued is the future of nutrition science.
Old guideline: Not addressed.
2015 guideline: Up to 5 cups a day.
Earlier this year, the federal advisory committee that helps write the Dietary Guidelines for Americans weighed in on coffee for the first time and concluded that drinking up to five cups a day can be part of a "healthy lifestyle." The group wrote that "strong and consistent evidence shows that consumption of coffee within the moderate range is not associated with increased risk of major chronic diseases."
It also said that consuming as many as five cups of coffee daily was associated with health benefits, such as reduced risk of heart disease and type 2 diabetes. Those pronouncements are supported by dozens of studies showing that, on average, people who drink coffee are no worse off than those who don't.
Old guideline: Consume proteins such as lean meat, poultry and seafood as part of a balanced diet but replace foods high in solid fats with those that are lower in solid fats and calories and/or are a source of oils.
2015 guideline: Eat a variety of protein foods, including seafood, lean meats and poultry, eggs, legumes (beans and peas), soy products, and nuts and seeds. Get less than 10 percent of daily calories from saturated fats and meats that are high in saturated fat. Teen-aged boys and men should "reduce their overall intake of protein foods" such as meat.
Old guideline: Limit sodium to 2,300 milligrams a day — but 1,500 milligrams daily for anyone who is older than 50 or African-American.
2015 guideline: Adults and children ages 14 years and older should limit sodium to less than 2,300 mg daily, and children younger than 14 should consume even less.
Most nutritionists agree that consuming too much salt can be dangerous to your health.
The federal government is on the side urging that Americans aggressively limit salt intake. It has warned that most people were eating dangerous amounts of salt that could increase their risk of high blood pressure and heart issues. New guidelines maintain a daily limit of less than 2,300 milligrams of sodium — about a teaspoon of salt.
Old guideline: Restrict cholesterol intake to 300 milligrams daily.
2015 guideline: No limit is included, but "this change does not suggest that dietary cholesterol is no longer important to consider when building healthy eating patterns. ... Individuals should eat as little dietary cholesterol as possible."
Cholesterol warnings have helped shift eating habits from foods like eggs. But scientific thinking has evolved.
Nutritionists now believe that foods high in cholesterol may not significantly affect cholesterol levels or increase the risk of heart disease in healthy adults. But individuals with health issues such as diabetes should continue to avoid cholesterol-rich foods.
Old guideline: Replace whole milk and full-fat milk products with fat-free or low-fat choices.
2015 guideline: Healthy eating patterns limit saturated and trans fats. Less than 10 percent of your daily calories should come from saturated fats. Foods that are high in saturated fat include butter, whole milk, meats that are not labeled as lean, and tropical oils such as coconut and palm oil. Saturated fats should be replaced with unsaturated fats, such as canola or olive oil.
Many Americans believe that saturated fat found in products like whole milk, butter and red meat is a dietary evil. But many nutritionists say that judging food based solely on its fat content obscures other possible health benefits.
Numerous studies have appeared to show that saturated fat raises the risk of heart disease, but new research suggests that you can't just replace it with "low fat" carbs like bread and cookies.
Old guideline: Limit intake of added sugars, which are sweeteners added during processing or preparation or consumed separately.
2015 guideline: Less than 10 percent of daily calories should come from added sugars. (These do not include naturally occurring sugars such as those consumed as part of milk and fruits.)
Sugar has become the principal poison in our diets — blamed by many nutritionists and public health officials for myriad health ills, including the obesity epidemic and chronic conditions like diabetes and heart disease. But scientists remain split on whether sugar is the cause of these ailments or whether it's part of a larger problem of Americans taking in too many calories.
The major sources of added sugars are beverages, snacks and sweets. Experts say you don't need to cut those out of your diet completely; just try to shift away from having so many servings of them.