Part D. Chapter 1: Food and Nutrient Intakes, and Health: Current Status and Trends
Humans require a wide range of essential micronutrients and macronutrients for normal growth and development and to support healthy aging throughout the life cycle. Essential nutrients, including most vitamins, minerals, amino acids and fatty acids, water and fiber, must be obtained through foods and beverages because they cannot for the most part be endogenously synthesized, or are not endogenously synthesized in adequate amounts to need recommended intakes. Understanding the extent to which the U.S. population and various age, sex, and racial/ethnic groups within the population achieve nutrient intake requirements through available food and beverage intake, including foods and beveragesiv that are enriched or fortified, is an important task of the DGAC. Notably, the DGAC considers that the primary source of nutrients should come from foods and beverages. Nutrient-dense forms of foods (those providing substantial amounts of vitamins, minerals and other nutrients and relatively few calories) are recommended to ensure optimal nutrient intake without exceeding calorie intake or reaching excess or potentially toxic levels of certain nutrients.
In the process of evaluating adequacy of nutrient intake of the U.S. population, the DGAC identified two levels of “Nutrients of Concern”. Shortfall nutrients are those that may be underconsumed relative to the Estimated Average Requirement (EAR) or Adequate Intake (AI). Overconsumed nutrients are those that are consumed in amounts above the Tolerable Upper Limit of Intake (UL)1 or other nationally recognized standard.2 Nutrients of Public Health Concern were those shortfall or overconsumed nutrients that also had evidence of under- or overconsumption through biochemical nutritional status indicators3 plus evidence that the nutrient inadequacy or nutrient excess is directly related to a specific health condition. This information is critical in determining where dietary intake improvements may be warranted that will benefit the health of the population. The 2015 DGAC recognizes that the 2010 DGAC specifically addressed whether or not multivitamins provided health benefits. The 2015 DGAC did not specifically address multivitamins, but recognizes that some dietary supplements may be recommended for some populations or life-cycle phases (pregnancy, for example).
In addition, many foods contain constituents that enable them to be produced, preserved, and thus widely available year round. Some of these ingredients, such as sodium, are used to make foods shelf stable and can help ensure food availability and food security for the population as a whole.4 Other ingredients, such as added sugars, are used as a food preservative and to enhance palatability. Despite the functional nature of both sodium and added sugars in the food supply, excess consumption of these dietary constituents poses potential health risks and was of particular concern to the DGAC. This chapter reviews data on intakes of sodium, added sugars and saturated fat; other chapters consider sodium, added sugars, and saturated fat from additional perspectives (see Part D. Chapter 6: Cross-Cutting Topics of Public Health Importance) including health outcomes. The food supply also contains ingredients that are both naturally occurring and also added to foods and beverages, such as caffeine, that have generated considerable attention in recent years. This chapter examines intake levels across age and sex groups of the U.S. population; Part D. Chapter 5: Food Sustainability and Safety considers several safety aspects of caffeine consumption.
The U.S. food supply is complex. Tens of thousands of foods and food products are available in a variety of forms. Some foods are whole foods that are often eaten alone without additions, such as fruit and milk, while others, such as sandwiches and mixed dishes, are mixtures of multiple components from more than one food group.
The DGAC recognizes the importance of understanding the totality of food and beverage intake at the level of food groups and basic ingredients (e.g., fruit, vegetables, whole grains, refined grains, dairy, protein foods) as well as at the level of foods as they are typically consumed, called food categories (e.g., pizza, pasta dishes, burgers, sandwiches) and how these contribute to nutrient adequacy or nutrient excess. To better understand current food intakes of the U.S. population, the Committee reviewed data on several issues, such as which of these food groups (e.g., refined grains) and food categories (e.g., sandwiches, beverages, snacks and sweets) contribute the most energy (calories), sodium, and saturated fat.
Understanding the totality of food and beverage intake also involved acknowledging that individuals purchase and procure food in a diverse array of locations, including large grocery stores, convenience stores, schools, the workplace, quick-serve restaurants, and sit-down restaurants. The DGAC examined the diet quality of the foods and meals at each major procurement point, as it is important to understand not only where foods are purchased or obtained, but also the extent to which they contribute to the overall nutritional adequacy and nutritional quality of the diet. This information may be relevant to guidance for federal nutrition programs. The DGAC also considered the diet quality of foods prepared and purchased at places such as supermarkets, but consumed at home. For example, many supermarkets have salad bars and hot food bars, but these foods are then consumed at home. However, on examination, it was determined that these types of data were not available. The DGAC also examined eating behaviors, such as meal skipping, and identifying which nutrients and how much energy are consumed at specific eating occasions and locations, because an understanding of these behaviors can help inform public policy and population as well as individual guidance.
The DGAC considered the composition of dietary patterns that were found to be linked to health outcomes in Part D. Chapter 2: Dietary Patterns, Foods and Nutrients, and Health Outcomes. Understanding the characteristics of diets characterized as “Healthy U.S.” or “Mediterranean-style” dietary patterns and others patterns found to have health benefits, will provide specific, healthful food and beverage-based guidance for the U.S. population. These patterns are defined using dietary quality/adherence indices, [e.g., Healthy Eating Index (HEI)], based upon data-driven approaches (e.g., cluster or factor analysis), or may be self-identified patterns (e.g., vegetarian).
To address the issues described above, the DGAC presents the current status and trends in nutrient, food, food group, and food category intakes, and describes major sources of energy, sodium, added sugar, and saturated fat, and dietary pattern intake among representative samples of the U.S. population from the National Health and Nutrition Examination Survey (NHANES) What we Eat in America (WWEIA) dietary survey.5 We also describe eating behaviors, such as number of meals per day, diet quality of foods, location of food purchase and consumption and diet quality of foods based on location where the food was purchased or consumed.
Finally, we describe the prevalence of diet-related health outcomes in the U.S. population, including obesity, diabetes, cardiovascular diseases, certain cancers, osteoporosis, congenital anomalies and psychological health (including mental health), and neurological illness (such as Alzheimers Disease). The examination of diet-related health outcomes was more extensive than in earlier DGAC reports. The high rates of the chronic conditions and the presence of other less common, but important diet-related health problems, provided compelling reasons to study them in greater detail. These data provide a backdrop for other chapters, particularly those which examine the strength of associations between diet and health outcomes (Part D. Chapter 2: Dietary Patterns, Foods and Nutrients, and Health Outcomes) and methods for improving disease risk outcomes and improving health at individual (Part D. Chapter 2: Dietary Patterns, Foods and Nutrients, and Health Outcomes and Part D. Chapter 3: Individual Diet and Physical Activity Behavior Change and population levels (Part D. Chapter 4:Food Environment and Settings).
One of the overarching motivations for this broad examination of nutrient intake, food group and food category intake, and food purchase location is to better understand the relationship of food intake (both inadequacy and excess) and the food environment to nutrition-related health conditions. This comprehensive evaluation of food and nutrient intakes by the U.S. population (and various subgroups) along with the food and eating environment enables the consideration of factors on a broad scale that may facilitate behavior change and adoption of healthy eating practices in the population at large. Taken together, these dimensions of our analysis inform the remaining chapters in the report, which, taken together, will provide the contextual and scientific foundation for the 2015 Dietary Guidelines for Americans.