2015 Dietary Recommendations Cover New Ground
A scientific report outlining new recommended dietary guidelines is already drawing attention in Washington D.C.—less for its fresh take on optimal diets than for its policy suggestions—and some of the authors joined a symposium hosted at the Harvard T. H. Chan School of Public Health (HSPH) yesterday to discuss their work. Against a stark background of data showing that more than two-thirds of Americans (155 million people) are obese or overweight, members of the 2015 Dietary Guidelines Advisory Committee (DGAC), selected for their expertise in nutrition and disease, recommend less meat, sugar, and refined carbohydrates. Gone are the limits on fat as a proportion of caloric intake: instead, the experts recommend capping consumption of saturated fats at 10 percent of total calories, and no longer suggest a limit on healthy, unsaturated fats, such as those found in vegetable oils and nuts. Eggs and shrimp, nutrient-rich foods once vilified for their cholesterol content, are back on the menu now that scientific evidence shows only a weak link between dietary cholesterol and cholesterol levels in the blood.
The recommendations of the independent, volunteer DGAC are used by the U.S. Departments of Agriculture (USDA) and Health and Human Services (HHS) to inform and update the federal Dietary Guidelines for Americans, the rules that shape implementation of a host of federally funded programs and initiatives, including meals served in schools. The new report’s inclusion of policy suggestions—such as a tax on sugar (which now contributes 13 percent of calories in the American diet) as one way to reduce public consumption of sweetened beverages and foods—raised the ire of some members of Congress. Some representatives have also criticized the report for addressing the sustainability of the food supply. The guidelines have considered food security since 1980, one member of the DGAC noted at the HSPH symposium, but have previously focused on current circumstances. Now the group, which has added seafood to the list of items considered beneficial for health, is considering the long-term impact of human consumption patterns on critical ecosystems such as global fisheries under the rubric “Food sustainability and Safety,” one of five areas highlighted in the report.
In the keynote address at HSPH, J. Michael McGinnis—now executive director of the Institute of Medicine Roundtable on Value & Science-Driven Health Care (part of the National Academy of Sciences) and previously a high-level administrator at HHS, emphasized that the scope of the recommendations reflects the fact that nutrition, which includes everything from food supply chains to food aid to research, is “fundamentally a systemic activity.” Ideally, he emphasized, “the Dietary Guidelines for Americans should offer the anchor reference point around which all food and nutrition policies can orient.”
McGinnis also outlined what he hoped would become goals for the next iteration of the report, due in 2020. These included more research on interaction among different nutrients; what “actually works” for weight reduction; and the ways in which individual biology and behavior influence health outcomes. He concluded with “a modest proposal:” that public and private partners work together to create “a sustained social-marketing message” that will promote public adoption of the healthy eating patterns identified in the report.
DGAC chair Barbara Millen, formerly a professor at the Boston University School of Medicine and now president of public health startup Millennium Prevention, then explained the scientific standards employed in the report. Randomized, controlled trials—the gold standard in public-health research—were given the most weight, she said; association studies that link behaviors or particular nutrients to health outcomes were accorded less importance. “Strong” recommendations in the 2015 report thus rest on firmer scientific foundations than ever before and represent, said Millen, “immediately actionable recommendations” to HHS.
Members of the committee, some of them reporting remotely via video feed, then presented key findings. They found that:
- 40 percent of the U.S. population doesn’t get enough of vitamins A, D, E, and C, nor folate, calcium, magnesium, fiber, and potassium—not surprising, perhaps, given that Americans don’t eat enough vegetables, fruits, whole grains, and dairy.
- Fully 70 percent of the population doesn’t eat the recommended quantities of fruit. What do Americans eat? The largest caloric contribution in most people’s diets comes from a category called “mixed dishes,” the largest component of which includes burgers and sandwiches.
- Many adolescent and pre-menopausal women are deficient in iron.
The shortfalls in calcium, vitamin D, fiber, potassium, and iron are considered “a public health concern” because underconsumption is linked to adverse health outcomes.
Consumption of saturated fat and sodium, on the other hand, exceed the maximal standard and thus pose health risks at the other extreme. The average American consumes more than 3,400 milligrams (mg) per day, while the upper recommended limit is 2,400 mg. The evidence that high sodium intake leads to high blood pressure is strong, reported DGAC committee member Frank Hu, professor of nutrition and epidemiology at HSPH and professor of medicine at Harvard Medical School (HMS). There is also moderate evidence of a link between sodium and cardiovascular disease, he reported.
The committee emphasized that a variety of different dietary patterns ranging from a “healthy U.S. style,” to vegan and Mediterranean style lead to healthy outcomes. Common to all of them, speakers emphasized, are vegetables, fruits, whole grains, fish/seafood, legumes, and nuts. Healthy diets include moderate amounts of low and non-fat dairy products and alcohol; limit processed and red meat; and are low in sugar-sweetened beverages and foods and refined grains.
Hu also conveyed the report’s finding of strong evidence that moderate coffee consumption (three to five cups a day) does not lead to increased long-term health risks in healthy individuals. In fact, coffee drinkers appear to have lower risk of type 2 diabetes and cardiovascular disease. The effects of caffeine itself are less well documented, he noted, but up to 400 mg a day is safe and may protect against Parkinson’s disease. Higher amounts may have adverse outcomes, especially when combined with alcoholic beverages. (The report also noted that coffee drinkers should minimize the amount of added cream, milk, and sugar.)
Earlier versions of the guidelines have already had a positive impact on children’s dietary choices while in school, noted one author somewhat ironically: “Kids are gaining weight in the summer,” indicating that schools, by contrast, are doing “a good job.”
Americans’ level of physical activity, however, is far below federal guidelines for both children and adults. Although 50 percent of adults report meeting the minimum recommendations for activity, research making use of accelerometers tells a different story. Those studies indicate that 90 percent of the population does not meet even the minimum recommendations for physical activity.
Stare professor of epidemiology and nutrition and HMS professor of medicine Walter Willett, an eminent expert on diet, ended the evening with a personal assessment of the report’s findings. Noting how difficult the work of such committees can be politically, he offered a constructive critique of the report’s findings that Americans don’t consume enough calcium. He pointed out that the scientific evidence for that assertion comes from studies of only two- to three-weeks’ duration that have shown no link to decreased bone health. The report guidelines, he continued, imply that Americans would need three servings of dairy a day to get enough calcium—a recommendation that would dictate a doubling of production, he argued, a massive expansion of the American dairy herd, and thus one that “clashes” with the DGAC’s own consideration of environmental impact.
He praised the committee for the enormous amount of work they had put in during the last two years, and concluded by highlighting several of the reports’s cutting-edge recommendations that will lead to better public health, including the removal of the cap on calories from fat as a percentage of a healthy diet, the suggested limits on consumption of red meat, the emphasis on foods rather than nutrients, and the inclusion of environmental issues that impact long-term sustainability of the food supply.