One brief paragraph about dietary cholesterol in a 500-plus page scientific report issued recently by the 2015 Dietary Guidelines Advisory Committee has overshadowed the rest of its primary conclusions. As a result, physicians can expect questions from patients confused by subsequent news reports who wonder which foods are considered healthy and which are not, and why expert opinion keeps changing.
The committee's report stating that dietary cholesterol should no longer be considered “a nutrient of concern for overconsumption” has generated much discussion and confusion, particularly after previous guidelines recommended that cholesterol-rich foods should be limited in a healthy diet. (A public comment period on the scientific report of the 2015 Dietary Guidelines Advisory Committee is scheduled to end on May 8, 2015. The final guidelines are expected by the end of this year.)
The Dietary Guidelines for Americans in 2010 had recommended that no more than 300 mg of dietary cholesterol be consumed each day. That recommendation, however, is no longer considered supportable by available evidence, which, the committee states, “shows no appreciable relationship between consumption of dietary cholesterol and serum cholesterol.”
This change in thinking about dietary cholesterol reflects evidence from accumulated years of research and is in line with recommendations from the American Heart Association (AHA) and the American College of Cardiology (ACC). The 2013 AHA/ACC Guideline on Lifestyle Management to Reduce Cardiovascular Risk, published in the July 1, 2014, Journal of the American College of Cardiology, cites insufficient evidence for supporting limited consumption of dietary cholesterol.
“Dietary cholesterol is not as important as what most of us were brought up to believe,” said Roger Blumenthal, MD, director of the Johns Hopkins Ciccarone Center for the Prevention of Heart Disease and The Kenneth Jay Pollin Professor of Cardiology at Johns Hopkins in Baltimore. Recent analyses have found that the percentage of people who are more susceptible to a significant increase in cholesterol if they eat cholesterol-rich food such as eggs is much smaller than previously believed, he said.
“Physicians need to be on the lookout for the small minority of people whose cholesterol numbers go up a significant amount if they start eating more dietary cholesterol,” he said. “It seems that the amounts of saturated fat and total calories in a person's diet are the big drivers of blood cholesterol going up rather than dietary cholesterol.”
Miriam Nelson, PhD, associate dean of the Tisch College of Citizenship and Public Service, professor of nutrition at the Friedman School of Nutrition Science and Policy at Tufts University in Boston, and a member of the 2015 dietary guidelines committee, agrees that elevated cholesterol is often connected to consumption of saturated fats.
“Eggs are fine, because an egg a day is a good-quality protein and doesn't have much saturated fat. You don't need to limit the number of eggs you are eating in a week. But if you fry that egg in lots of butter and put hollandaise sauce on it ... that's not so healthy,” said Dr. Nelson.
David Katz, MD, MPH, FACP, an internist and director of the Yale-Griffin Prevention Research Center in Derby, Conn., said that although few people need to be on a low-cholesterol diet, there is no strong reason to add eggs or seafood if a person is eating healthily.
“Going from a breakfast of, for instance, steel-cut oats, walnuts, and berries to a breakfast of eggs would be trading down,” he said. “The first is decisively beneficial, and the second is simply not harmful in the ways we once thought.”
He added, “Dietary cholesterol does not deserve the bad rap it has had, but it hasn't turned into spinach overnight either. There is no reason to try to add cholesterol to the diet, but there is also no reason to shun it.”
Sodas, burgers, snacks
The eating patterns for many Americans are not healthy, according to the dietary guidelines committee report. Americans, on average, consume diets that are low in vegetables, fruit, whole grains, and dairy. This underconsumption means that they do not get enough vitamins A, D, E, C, and folate; calcium, magnesium, and potassium; and fiber. Most Americans are also consuming too many calories and too much sodium, saturated fat, refined grains, and added sugars.
Seventy-five percent of the total energy intake in the American diet is derived from about half the subcategories of food, according to the report. Mixed dishes (such as burgers, sandwiches, and tacos), snacks and sweets, and beverages contribute more than 56% of energy intake in the U.S. population. Mixed dishes contribute heavily to the intake of energy, saturated fat, and sodium but do not provide enough vegetables, fiber, grains, or dairy, according to the report.
Preventable, chronic diseases such as cardiovascular disease, hypertension, type 2 diabetes, and diet-related cancers affect about half of all Americans and are linked with poor-quality dietary patterns and physical inactivity. About two-thirds of adults and about one-third of children and young people are overweight or obese, according to the report.
Dr. Nelson said the dietary guidelines committee is “promoting a healthy pattern of eating for Americans. You cannot isolate one piece like cholesterol and assume that diet is healthy. It is the pattern of eating that is critical.”
The 2015 report has defined a healthy dietary pattern as one that is:
- higher in vegetables, fruits, whole grains, low- or non-fat dairy, seafood, legumes, and nuts, without added salt or fat or sugar,
- higher in iron-rich foods among adolescent and premenopausal females,
- moderate in alcohol consumption among adults,
- lower in red and processed meats, and
- low in sugar-sweetened foods and drinks and refined grains, sodium, and saturated fats.
It is not necessary to eliminate food groups or conform to a single dietary pattern to achieve a healthy dietary pattern, the committee states. People can “combine foods in a variety of flexible ways to achieve health dietary patterns, and these strategies should be tailored to meet the individual's health needs, dietary preferences and cultural traditions,” the report states.
The report also revisited its previous guidance on salt, saturated fat, and added sugars and made the following recommendations:
- limit dietary sodium to less than 2,300 mg/d; flavor foods with spices and herbs instead of salt,
- limit saturated fat to less than 10% of total calories per day and substitute saturated fats with unsaturated fats, particularly polyunsaturated fatty acids, and
- limit added sugars to no more than 10% of total calories per day; sugars should be reduced and not replaced with low-calorie sweeteners.
It's not necessarily news that sugars, saturated and trans fats, and sodium are having an increasingly negative impact on the health of Americans and are largely consumed in processed foods and sweetened beverages, as the report found. “Five years ago we knew we were eating too much added sugar, refined starch, saturated fat, and processed food, and all of that is still true,” Dr. Katz said. “This report is noteworthy for its emphasis on foods, rather than nutrients. ... The fundamentals of healthy eating are, in fact, a matter of massive, consistent, global consensus.”
Anticipating the questions
With new guidelines every few years and news reports every few days touting the latest diet news, patients may be confused about what they should eat or not eat and may turn to their internists for guidance for answers to questions like the following.
What is the best diet overall? Strong and consistent evidence indicates that a healthy dietary pattern is higher in vegetables, fruits, whole grains, low-or non-fat dairy, seafood, legumes, and nuts, but Dr. Nelson noted that the scientific report is not suggesting that everyone should become a vegetarian. “If you want to, that's fine. We are talking, however, about eating less meat and more plants.”
Dr. Blumenthal noted that a strictly vegetarian diet is difficult for most people to follow. “Mixing in with some fish (1-2 times a week) and occasional lean meat in small portions provides variety and is more practical for most Americans. The most important thing, however, is the number of calories you take in and how many you burn up each day,” he said.
Are there certain foods that most people should avoid? This report and others indicate that most people eat too much red and processed meat, drink too many sugary beverages, and favor too much processed food, such as hamburgers. A healthy dietary pattern limits those foods and substitutes them with the recommended foods.
Is it safe for most people to eat eggs or other foods high in dietary cholesterol? Research has now concluded that only a very small percentage of people are sensitive to cholesterol dietary intake, but no one can predict which patients fall into that group. If cholesterol levels increase by a significant amount when those foods are added, the patient may be cholesterol sensitive.
What do the reports say about alcohol? This report and others, including one from the Center for Nutrition Policy and Promotion in 2014, have found strong and consistent evidence that adults can consume alcohol in moderation, such as 2 drinks per day for men and 1 for women, unless contraindicated.
What is the current thinking about saturated fats? The dietary guidelines committee report and others from the AHA and ACC assert that eating foods with saturated fats can contribute to high cholesterol and heart disease. The AHA recommends that only 5% to 6% of calories be derived from saturated fat each day; the dietary guidelines committee recommends less than 10%. Ways to achieve this are to eat lean meat and poultry, to remove the skin, to substitute fish or nuts when possible, and to drink low- or non-fat milk.
If a patient has a difficult time eating a healthy diet, what else can be recommended? According to this latest report, the “food environment” influences a person's diet and that of the family. The food environment includes the marketing and abundance of relatively cheap processed foods and meals. Dr. Nelson recommended talking with patients about the types of foods they have in their home, where they shop, where they buy meals out, and food choices available at work.
“You have to think about the whole food environment to help the patient have an easier time to eat well,” she advised.