April 1, 2015 | Erin Bluvas, bluvase@sc.edu 

With new dietary guidelines set to be announced later this year, consumers may be wondering what approach the U.S. Department of Agriculture and the Department of Health and Human Services, who jointly issue the Dietary Guidelines for Americans, will advocate for the next five years. How will the recommendations change and how will they be shared with the general public to incorporate into their daily lives? For many years, the Food Guide Pyramid served as the primary vehicle for providing consumer-friendly education about the guidelines to the public. In 2011, Choose My Plate replaced the pyramid. In addition, detailed healthy eating patterns (e.g., Mediterranean Diet, Dietary Approaches to Stop Hypertension, USDA Food Pattern) have emerged in recent years to help individuals understand the exact quantities, serving sizes, types of foods, etc. they should consume. But perhaps the specific pattern a person follows is less important than previously thought.

Angela Liese's research suggests this might just be the case. A professor in the Department of Epidemiology and Biostatistics at the Arnold School of Public Health, Liese is interested in behavioral influences on chronic diseases. She has a background in nutrition and has been studying dietary patterns for 15 years. "I believe there is a lot to be learned about how diet affects health if one focuses primarily on the foods and food groups," she says. As such, Liese has conducted numerous studies examining eating patterns using statistical methods.

It was this expertise that led the USDA Nutrition Evidence Library to invite Liese to join a technical expert panel on dietary patterns. The Library organized this panel in 2011 to prepare for the 2015 set of updated guidelines by consulting on the latest scientific evidence from a range of studies. However, through their work the panel realized that there was a gap in the existing research. Previous studies had not established a relationship between eating patterns and mortality, because the methods used to define these patterns were not standardized across the studies.

Based on her research experience with dietary patterns, Liese spearheaded and defined the key research questions that needed to be examined to move the field forward and generated the group for what became the National Cancer Institute-led Dietary Patterns Methods Project. Using standardized types of data analyses, the team analyzed and then compared the data from three cohorts in order to produce three separate, yet parallel evaluations. Each cohort included studies that examined four types of healthy eating patterns that are popular in the U.S., including the Healthy Eating Index 2010, Alternative Healthy Eating Index 2010, Mediterranean Diet and Dietary Approaches to Stop Hypertension.

The researchers' findings revealed that higher quality diets (i.e., adhering to the dietary recommendations within a given healthy eating pattern) were associated with reduced (11-28 percent) rate of mortality as well as cardiovascular disease and cancer when compared to lower quality diets. These linkages were consistent across all three cohorts and the four major types of eating patterns examined within each cohort. Moreover, these reductions in mortality risk became apparent at relatively lower levels of diet quality, suggesting that individuals with poor dietary habits can reduce this risk with even small improvements in diet quality.

Even better news for the public is that the differences in the specifics of the four healthy eating patterns may not matter that much. Because these findings demonstrate reduced risk of mortality, cardiovascular disease and cancer across multiple healthy eating patterns, this suggests that consumers can choose among any of these patterns--as long as they are grounded in the Dietary Guidelines for Americans or other recognized nutrition recommendations. This means that individuals have more flexibility to select healthy eating patterns that work with their specific life style and preferences. There is no single eating pattern that is right, and the others are wrong.

In terms of next steps, Liese believes that additional research is needed to learn more about whether there are certain aspects of specific eating patterns, as measured by their corresponding indices, that could serve as predictors of mortality that are just as reliable as the full eating pattern. "It will be important to determine if any of these connections exist, because it could mean that the dietary recommendations could actually be simplified," Liese explains. Emphasizing the relationship between eating patterns and reduced mortality/chronic diseases, as supported by statistical evidence, could be a game-changer for how people approach healthy eating and nutrition. "At the end of the day, practitioners and clinicians need to be able to tell the public which foods to eat and which foods to avoid in a way that they can understand," says Liese. This line of research could result in greater flexibility and simplified messaging among the options for healthy eating patterns, leading to a widespread impact on public health.