The High Cost and Unequal Cancer Burden of Poor Diet in the United States

Poor diet is known to increase cancer risk and mortality, both directly and mediated by excess body fatness.^1,2 Characterized by higher intakes of red and processed meat and sugar sweetened beverages (SSBs) and a lower intake of whole grains, vegetables, and fruit, poor diet is associated with the risk of multiple cancers, especially colorectal cancer.^1,2 The most recent estimates of the proportion of new cancer cases attributable to suboptimal diet range from 4.2%³ to 5.2%,⁴ equating to approximately 67 000 to 80 000 total cases per year in the United States. Disparities in cancer outcomes among racial and ethnic groups and by socioeconomic status are well documented.^5,6 For example, colorectal cancer death rates among Black males is more than 44% higher than among White males.⁵ Few studies, however, have quantified the impact of poor diet on cancer outcomes in these subgroups.

In this issue of AJPH, Wang et al. (p. 2008) estimate the lifetime health and economic costs of cancer attributable to poor diet among US subpopulations defined by age, sex, race/ethnicity, education, income, and Supplemental Nutrition Assistance Program (SNAP) participation. The authors projected both direct and indirect effects of poor diet, the latter derived from a pooled analysis of three prospective cohorts, to obtain diet–body mass index associations. Additionally, using publicly available data and modeling techniques, the authors estimated that the impact of suboptimal intakes of seven dietary factors (whole grains, dairy products, fruits, vegetables, red meat, processed meat, and SSBs) accounted for 3.04 million new cancer cases (7.4%) and 1.74 million cancer deaths (7.7%) among US adults over a lifetime. These percentages are higher than previous estimates, likely because of the authors’ use of lifetime modeling, whereas estimates from previous studies were for a specific year (i.e., 2014³ or 2015⁴). The authors also estimated $254 billion in medical costs attributable to poor diet (7.8% of direct medical costs of 15 diet-related cancers in the United States).

A valuable contribution by Wang et al. is the quantification of disparities in the diet-attributable burden of cancer in subpopulations by cancer type and by dietary factor. For example, the authors estimated that non-Hispanic Black persons would experience more diet-attributed incident cancers and cancer deaths than would non-Hispanic White persons, with a difference of 110 cases and 214 deaths per 100 000. With the exception of diet-attributed oral, pharyngeal, and laryngeal cancers, which was highest among White persons, this disparity applied to all cancers studied, but particularly colorectal cancer. This higher burden was greatest for low consumption of dairy and whole grains and for excess consumption of processed meats and SSBs.

Having attained less than a college education was also associated with a higher number of diet-attributable cancer cases and deaths compared with adults with a college degree (excess cases and deaths of 180 and 132 per 100 000, respectively). The largest differences were seen for colorectal cancer and applied to all dietary factors, most notably SSBs. Low family income and SNAP participation were associated with higher diet-attributable cancer cases and deaths, with the largest disparities related to consumption of SSBs and low consumption of whole grains. Approximately 72% of the cases associated with poor diet were attributed to direct diet–cancer etiologic effects, with the remainder mediated by body mass index.

ORIGINS OF DISPARITIES

The reasons for disparities in diet-related health outcomes are multifactorial and complex, with major aspects rooted in structural and social marginalization and discrimination, which result in poorer living environments, limited educational and occupational opportunities, and lower incomes among people of color and other historically marginalized populations.⁷ Consequently, these populations often experience higher levels of unhealthy food marketing and lower access to healthy foods because of a lack of financial and other resources, including transportation insecurity. This is compounded by limited access to supermarkets with healthy, affordable, high-quality choices but high availability of low-cost, poor quality “fast foods” and less healthy foods from convenience stores.¹ Even when supermarkets are available, healthier foods are often more expensive.⁸ Disconcerting trends of widening gaps in diet quality have been documented by education and income.⁹

PUBLIC HEALTH IMPLICATIONS

Eliminating health inequities through addressing structural racism and improving social determinants of health, which influence factors such as education, wages, housing security, and access to medical care, will need greater societal efforts to address these fundamental causes of poor health. However, some nutrition interventions may help reduce disparities in ensuring food and nutrition security so that individuals have a fair chance at a healthy diet pattern. Several policy implications and approaches are enumerated by Wang et al. For example, the authors suggest priority targets for behavior change and policy strategies to reduce these disparities, including incentives and disincentives to steer SNAP food purchases and improving access to whole grains, fruits, and vegetables, as well as disincentives, such as taxation or labeling, to discourage SSB and processed meat consumption. SSB consumption emerged as a key target in this work; various policy approaches— including taxation—have proven successful in several countries, regions, and cities,¹⁰ although few places in the United States have made progress in adopting these policies in the past few years.

Improving availability of drinking water and affordable, healthy, culturally appropriate foods in low-income and racial/ethnic minority communities are other approaches to addressing these gaps. Produce prescription programs and financial incentives for purchasing fruits and vegetables among SNAP participants are showing promise in US-based studies.¹¹ In these programs, when a person purchases produce with SNAP funds, they receive additional funds to spend on fruits and vegetables. Medically tailored meals are emerging as a way to support risk reduction and disease self-management. Reducing the marketing of unhealthy foods and beverages has also shown promise as a strategy. Finally, to inform policy and program efforts, there is a need for more implementation research on interventions that aim to reduce disparities.

STUDY STRENGTHS AND WEAKNESSES

The study by Wang et al. provides important evidence on diet-related cancer and economic disparities that can be used to inform future efforts to improve health equity. Despite its many strengths, this study also has limitations, some of which are acknowledged by the authors. For example, they used data on diet in people aged 20 years and older from surveys conducted in 2015 to 2018 to estimate diet across the life course, not taking into account any potential changes in diet over different periods or the effects of early life diet on cancer outcomes, although the latter has not been extensively investigated in other similar studies either. In addition, more research is needed on indirect effects of diet on cancer through body mass index and on any differences in associations between diet and cancer risk by race/ethnicity; in this study, the authors used the same estimates for all racial/ethnic groups.

STUDY TAKEAWAYS

Food insecurity, at high levels in the United States because of the COVID-19 pandemic, is likely to exacerbate already existing racial and economic health inequalities. If left unaddressed, the disparities in diet quality, the disparities in the proportion of diet-preventable cancers, and the high economic costs identified by Wang et al. will continue or worsen. Innovative and societal solutions are required at national, state, territorial, tribal, and local levels to make it possible for all individuals to have the ability to follow dietary recommendations and cancer-prevention guidelines for optimal health and quality of life.