Dietary guidelines for cancer prevention are similar across prominent public health organizations. In spite of a general scientific consensus on the importance of a healthy diet for cancer prevention, the actual diets of a large proportion of America's youth are not aligned with these dietary recommendations. Pre-adolescents and adolescents tend to fall short of recommendations for fruit, vegetable, and whole grain consumption. Furthermore, an unhealthy proportion of their diet is composed of energy-dense foods that are high in fat (such as red and processed meats), refined sugar (such as refined grains and SSBs), and/or salt.
Improving dietary behaviors poses many challenges. Among youth, dietary behaviors are influenced by numerous factors at multiple levels: individual, interpersonal, community, and society levels [11
]. Identifying key influential factors may inform future public health policies and practices. For example, adolescents generally do not have the same level of control over their food intake that adults do, and much of the responsibility to support healthy eating habits falls on parents [46
]. Parents tend to be influenced by socioeconomic factors, and changes to food pricing offer a potential strategy for dietary improvements [11
]. Another example is the school food environment which plays a key role in proper nutrition. Millions of children and adolescents rely on federally-supported school breakfast and lunch programs [47
]. Yet participation in the school meal program has been shown to be associated with an increased prevalence of excessive sodium intake [49
]. Such findings suggest that improvements to the school meal program alone could have a positive impact on the quality of youth's diets.
When assessing the dietary behaviors among youth related to cancer prevention, we face several limitations. First, dietary intake data from both NHANES and YRBS rely heavily on self-reported information, which can be subject to bias and error. NHANES dietary intake data are collected via multiple 24-hour dietary recalls which may be less prone to error than other dietary recall methods [50
]. NHANES data for BMI is based on height and weight measurements which are considered more accurate than self-reported height and weight, as are used in the national YRBS [51
]. Second, dietary recommendations for cancer prevention tend to be based on knowledge related to adults' dietary behaviors, and there is insufficient evidence to know how strongly dietary habits during childhood predict lifetime dietary patterns [52
]. Epidemiological studies suggest that unhealthy dietary habits that develop early in life and persist into adulthood may increase the risk of some cancer types, but additional research is needed to better understand the degree to which childhood dietary patterns relate to subsequent cancer risk later in life [56
]. Additionally, the relationship between cancer and certain diet-related factors may not necessarily be the same throughout the lifespan, as has been observed for obesity and breast cancer [57
]. Third, our understanding of the risks associated with potential carcinogens in the diet are often based on the effects of such contaminants in adults. These contaminants may be metabolized differently in a child's or adolescent's body due to differences in body size and composition, and youth have a "unique vulnerability" to the effects of chemical, physical, and biological agents [59
]. This difference may have implications for age-specific recommendations regarding potential carcinogens in youth diets.
Cancer etiology and cancer risk assessment are dynamic fields of scientific investigation, and our understanding about the role of diet in cancer occurrence is continually evolving. As a result, the dietary recommendations for cancer prevention examined in this review may change over time. For example, although the consumption of fruits and vegetables has long been associated with lower risks for certain types of cancers, recent research suggests that the consumption of fruits and vegetables may not be as protective against cancer as had been previously assumed [62
]. The potential cancer risks associated with low levels of exposure to certain chemicals are being reassessed in the face of evidence of upstream effects such as changes in hormone levels and immune function [64
]. Such chemicals are not addressed in the major dietary guidelines for cancer prevention, and more research is needed to determine if the levels of exposure to these contaminants in the United States is cause for a health concern [24
]. Research evaluating the health effects of these chemicals is particularly important to protect the health of children, who are generally thought to be more susceptible to carcinogens than adults [65
]. In the future, further advances in our scientific knowledge may reduce current uncertainties about diet and cancer and present new opportunities to reduce cancer risk.
This review illustrates discrepancies between expert recommendations about diet and cancer and actual dietary practices among youth and points to the need for more research to better promote the translation of science into practice. Data from the 2003 Health Information National Trends Survey (HINTS) suggests that at least half of the general population in the U.S. is aware that a healthy diet may reduce one's cancer risk [66
]. Although education and awareness about healthy eating for cancer prevention are important, interventions that make healthy options the default choice regardless of education, income, or other societal factors, change the environmental context in which dietary choices are made and may have a greater impact on the eating behaviors of America's youth [67
]. Future research should focus on developing and evaluating policies and interventions at the community, state and national levels for aligning the diets of American youth with the evolving scientific evidence regarding the role of diet in cancer incidence, as well as monitoring the long-term impact of different dietary patterns in childhood on cancer incidence later in life. If such public health efforts were successful, it could potentially reduce future cancer rates and improve the overall health of America's youth [4