1. Introduction
The US food supply provides an overabundance of energy and nutrients [
1]; however, most children do not consume the amounts and types of foods consistent with dietary recommendations [
2,
3]. Children, especially young children, have high nutrient needs for growth and development, but relatively modest energy requirements, leaving little room for energy-dense, nutrient-poor foods in the diet [
4]. Thus, it is important to encourage nutrient dense food choices and diets. Dietary preferences are established early in life [
5,
6,
7]. Establishing a healthful diet in childhood may help reduce the risk of developing diet-related chronic diseases in adulthood [
8,
9,
10].
Critical nutrition concerns for US children include excessive intake of energy which may increase the risk for weight gain and development of obesity. Data from the 2007–2008 National Health and Nutrition Examination Survey (NHANES) showed that among children 2 to 19 years (y), 31.7% were overweight and 16.9% were obese [
11]. Overweight/obesity in children has been associated with adverse lipid levels, blood glucose derangements, elevated blood pressure [
12,
13,
14], behavioral and psychosocial problems [
15,
16], and adult atherosclerosis [
17] and obesity [
12,
13,
14,
18]. Excess consumption of saturated fatty acids (SFA) has been associated with increased plasma total and low-density lipoprotein cholesterol in childhood [
19,
20,
21], which could increase cardiovascular disease risk; however, recent research has brought this association into question [
22,
23]. Inadequate consumption of foods rich in dietary fiber, vitamin D, calcium, and potassium [
24,
25] are major public health concerns. Intake of dietary fiber has been associated with decreased heart disease, obesity, and type 2 diabetes risks [
26]. Inadequate intake of nutrients, such as vitamin D and calcium, in combination with a sedentary lifestyle in childhood, can impede the achievement of maximal bone mineral content and density, thereby increasing the diet-related risk of developing osteoporosis later in life [
27]. In childhood, overconsumption of sodium, especially with inadequate intake of potassium, has been associated with hypertension [
28].
Recent detailed analyses of data on dietary sources of energy and nutrients in US children are lacking. In 1998, Subar
et al. [
29] reported disaggregated dietary sources of energy and nutrients among US children from the 1989 to 1991 Continuing Survey of Food Intakes by Individuals (CSFII). Recently, using data from the 2003–2004 or 2005–2006 NHANES, dietary sources of total energy and energy from solid fats and added sugars, respectively, were reported [
30]. The purpose of this study was to update previous research by examining dietary sources of energy and 28 nutrients using data from a recent nationally representative sample of US children 2 to 18 y. Understanding what children are consuming can help shape appropriate interventions to improve their diet and ultimately their health.
4. Discussion
The detailed analysis of children’s nutrient intake by Subar
et al. [
37] used data from the 1989–1991 CSFII that is now more than two decades old. Since then, forces driving trends in children’s food/beverage consumption have included an increased number of meals consumed outside the home [
43]; trade liberalization which has increased the number of foods available [
44]; changing beverage [
45,
46], food [
47], and snacking preferences [
48]; availability of competitive foods in schools [
49]; and food product reformulations in response to consumers’ health concerns [
50]. More recent data [
30] only provided information on total energy, solid fat, and added sugar intake among children. Thus, it was important to provide a more detailed analysis of children’s diet using recent nationally representative data. Faced with a pediatric obesity epidemic, it is important to identify principal sources of energy. This study showed that major sources of energy in children’s diets are not necessarily the same food groups that provide rich sources of nutrients. Of the 10 highest ranked foods/food groups, five groups including milk, yeast bread/rolls, cheese, poultry, and beef accounted for approximately 27% of energy intake; these foods/food groups provided a variety of nutrients, including calcium, vitamin D, and potassium. In their lowest fat form, these foods/food groups are recommended by MyPlate [
51]. In contrast the other five food/food groups that were major energy sources (27% combined): cake/cookies/quick bread/pastry/pie, crackers/popcorn/pretzels/chips, soft drinks/soda, fruit drinks/ades, and candy/sugars/sugary foods, contributed mainly fat or added sugars and few other nutrients. That many of the major sources of energy are nutrient-poor foods is consistent with reports that many children do not follow dietary recommendations, and without consuming recommended amounts of nutrient-dense foods, such as whole grains, fruit, vegetables, low-fat milk, and lean meat, diets can be nutritionally inadequate [
3].
Soft drinks/soda and fruit drinks/ades contributed 5.5% and 3.5% of energy, respectively; if these two sweetened beverage categories were combined, they provided a higher percentage (9%) than any other source of energy in the diet. Subar
et al. [
29] also showed that soft drinks and soda were major contributors of energy to the diets of children (4.3%); however, in that study, fruit drinks provided only 2.2% of energy intake. Reedy,
et al. [
30] also reported soft drinks and soda as a major source of energy. From 1977 to 2006, children’s beverage consumption patterns changed and intake of sweetened beverages increased from 87 to 154 kcals [
45].
Subar
et al. [
29] reported that the five highest ranked energy sources were milk (11.7%), yeast bread (9.3%), cakes/cookies/quick breads/donuts (6.2%), beef (5.7%), RTEC (4.5%), and soft drinks/soda (4.3%). A comparison of that study and ours suggests a temporal shift in sources of energy occurred. Since our study combined crackers/pretzels with popcorn/chips, and candy with sugars/sugary foods, the ranking of the combined groups was higher than each of the individual groups studied in Subar’s study.
Data from children in the 2005–2006 NHANES [
30] showed the five highest ranked sources of energy were grain desserts (e.g., cakes) (6.8% of total energy consumed), pizza (6.7%), soda (5.8%), yeast breads (5.6%), and chicken (5.6%). In that study, mixtures were not disaggregated. Grain desserts and soda were identified in that study and ours as major contributors of energy to the diets of children. The study using 2005–2006 NHANES data separated milk by fat level, and therefore milk was not identified as a major source of energy in children’s diets; however, if whole and reduced-fat milk were combined they contributed the highest percentage of energy to the diet.
The same five highest sources of protein were identified by Subar
et al. [
29], albeit with a different rank order. Cheese and milk were the two highest ranked sources of SFA, followed by frankfurters/sausages/luncheon meats. The contribution of SFA in the diet by milk, beef and frankfurters/sausages/luncheon meats shown in our study was lower and cheese and crackers/popcorn/pretzels/chips was higher when compared with the 1989–1992 CSFII data [
29]. Current dietary recommendations are to replace SFA with mono-unsaturated fatty acids (MUFA) and poly-unsaturated fatty acids (PUFA) [
25] since the latter are associated with decreased cardiovascular risk [
52]. Our study showed that of the five highest ranked sources of MUFA (cake/cookies/quick bread/pastry/pie, frankfurters/sausages/luncheon meats, other fats/oils, beef, and crackers/popcorn/pretzels/chips) (
Supplemental Tables); beef was the only nutrient dense food. Of the five highest ranked sources of PUFA, poultry was the only nutrient-dense food. Intake of nutrient dense sources of oils, such as nuts, should be encouraged (
Supplemental Tables).
The 2010 Dietary Guidelines for Americans recognized the low intakes of dietary fiber, calcium, vitamin D and potassium were of public health concern [
25]. Ideally, diets or food patterns containing adequate amounts of these nutrients should be recommended so that intake of nutrient-dense foods can be consumed without unduly increasing energy intake. In children, dietary fiber intake is inversely associated with serum cholesterol levels [
53] and constipation [
54], a major cause of morbidity in children [
55]. Dietary fiber intake by children is approximately half of what is recommended [
56]. Fruit was the highest ranked source; however, most children do not consume the recommended amount of fruit [
3]. Fruit, yeast bread/rolls, crackers/popcorn/pretzels/chips, potatoes, RTEC, biscuits/corn bread/pancakes/tortillas, legumes, and cake/cookies/quick bread/pastry/pie provided a cumulative 58.5% of fiber intake. Of these foods/food groups, fruit, yeast bread/rolls, potatoes, RTEC, and legumes provide other nutrients while most of the other food/food groups do not. Cake/cookies/quick bread/pastry/pie provided both fat and added sugars and were poor sources of most other nutrients. Because vegetables were split into many different categories, vegetables, other than potatoes, each contributed 4% or less of dietary fiber; however, when categories contributing at least 1% of fiber (e.g., tomatoes and tomato/vegetable juice, “other” vegetables, corn/peas/lima beans; carrots/sweet potatoes/winter squash; broccoli/spinach/greens) were combined, they would be the highest ranked source, providing 10.7% of fiber.
The nutrient contribution of milk and dairy products play an important role in helping American children and adolescents meet recommendations for short-fall nutrients [
24] and nutrients of public health concern [
25]. In our study, milk was an important source of calcium, potassium, vitamin D, and provided many other nutrients, including vitamin A, thiamin, riboflavin, vitamins B6 and B12, phosphorus, magnesium, and zinc (
Supplemental Tables). Subar
et al. [
29] found that in 1989–1991, milk (including milk drinks) and cheese provided 51.5% and 14.3% of children’s calcium intake. Sources of potassium were not reported in that study, and vitamin D food composition data were not updated or complete when that study was conducted. In our study, milk and milk drinks provided a lower percentage (38.2%), while cheese (19.4%) and other sources such as calcium-fortified fruit juice (3.2%) provided higher percentages of calcium intake than previously reported [
29]. A comparison of energy sources shows milk and milk drinks contributed a lower percentage of energy in 2003–2006 than in 1989–1991, while energy contributed from less nutrient-dense foods and beverages increased. This observation is consistent with other reports [
57,
58,
59]. Low-fat and reduced-fat milk are recommended for children after the age of 2 years.
This study has several limitations. Food grouping can have a major influence on the ranked order of dietary sources; thus, caution is advised when comparing these data to previous reports [
29,
30] if there were differences in the level of aggregation (
i.e., the number of food groups) or disaggregation procedures used to include ingredients in food groups. Study outcomes are based on self-reported data that tend to underestimate energy intake [
60]. A parent/guardian of children 2–11 y who was a proxy or assistant during the 24-h recall interview can often accurately report what the child consumed at home [
61] but may not know what the child consumed outside the home [
62]. A single day’s intake is not representative of an individual’s usual intake. However, the mean of the intake distribution drawn from a large, representative sample of a group is not affected by day-to-day variation [
63], and since the contribution of food sources is based on mean intake data from NHANES, the use of a single 24-h recall was appropriate [
64]. In general, because the food grouping in the USDA DSN database does not include ingredients of manufactured foods, disaggregated foods represent mixtures that are prepared from recipes. The USDA reduces the sodium content of mixtures if the respondent never, rarely, or occasionally uses salt in cooking, and the food was prepared at home; therefore, a large portion of the salt was added to recipes for foods prepared by restaurants, schools, and other establishments (data not shown). Finally, the updated vitamin D database that USDA recently released was appropriate for use with the 2005–2006 NHANES dietary intake data, and because vitamin D intake from foods consumed in 2003–2004 was determined using the updated food composition data, the 2003–2004 intake data may not have been representative of that time period. Any variation in food composition data affects the reliability of dietary intake estimation. It should also be noted that the major sources of vitamin D are fortified foods; changes in vitamin D fortification are regulated by a food additive rule [
65]. A petition to add vitamin D to calcium-supplemented juices and fruit drinks was approved by the Food and Drug Administration and implemented in 2004 [
66]. However, this change was effective only in the 2005–2006 NHANES, since the new calcium- and vitamin D-supplemented foods were not reported in the 2003–2004 NHANES.
