Food 'Swamps' Tied to Elevated Mortality From Obesity-Related Cancers

U.S. counties where fast-food joints exceedingly outnumber supermarkets and other fresh food options -- so-called food swamps -- were more likely to have high mortality rates from cancers related to obesity, a cross-sectional ecologic study found.

In fact, the odds of a high death rate from such cancers was 77% greater in counties with high food-swamp scores (adjusted odds ratio [aOR] 1.77, 95% CI 1.43-2.19), reported researchers led by Malcolm Seth Bevel, PhD, MSPH, of the Georgia Cancer Center in Augusta.

And as the group argued in JAMA Oncology, food swamps may be "a more comprehensive and novel indicator of the typical U.S. food environment compared with food deserts."

By comparison, the likelihood of a high death rate from obesity-related cancers was 59% greater in counties with high scores for food deserts (aOR 1.59, 95% CI 1.29-1.94) -- with these defined as low-income regions where people live far from a grocery store.

"The established existence of food deserts and the emergence of food swamps can be explained by a few theories," Bevel and coauthors explained. "One proposed theory is that chain grocery stores (e.g., Kroger, Sprouts, and Publix) lack a vested interest in remaining in urban neighborhoods with lower socioeconomic status (where most of the population is often composed of racial and ethnic minority groups) for longer periods, thus creating a food desert."

This, coupled with the increasing growth rate of fast-food restaurants that often target lower-income urban neighborhoods, have over time transformed deserts into swamps, according to the researchers. Another theory is that disparities in food environment "can be traced to the historic and resurging discriminatory practices of gentrification and redlining."

In either food environment scenario, Bevel's team observed a dose-response relationship when the obesity-related cancer mortality rates were broken down into tertiles:

• Moderate food-swamp score: aOR 1.29 (95% CI 1.03-1.61)
• High food-swamp score: aOR 2.10 (95% CI 1.67-2.63)
• Moderate food-desert score: aOR 1.43 (95% CI 1.15-1.78)
• High food-desert score: aOR 1.59 (95% CI 1.28-1.96)

Along with tobacco use and alcohol consumption, exercise, weight, and diet are considered the top modifiable risk factors for cancer.

But the current study "uncovers the misnomer of the generalizability of the concept of diet being a modifiable risk factor," wrote authors of an editorial accompanying the study.

"The complexities that prevent healthy food access are rooted in historical and structural factors, such as community disinvestment and systematic racism," said Karriem Watson, DHSc, MS, MPH, of the National Institutes of Health in Bethesda, Maryland, and Angela Odoms-Young, PhD, of the College of Human Ecology at Cornell University in Ithaca, New York. "Moreover, the causes of both obesity and cancer are complex. Consequently, the mechanisms that link low-resource food environments to obesity-related cancers may operate through multiple pathways rather than dietary consumption alone."

As defined by the International Agency for Research on Cancer, the 13 obesity-linked cancers include those of the breast, colorectum, endometrium, esophagus, gallbladder, stomach, liver, kidney, pancreas, ovaries, and thyroid, along with multiple myeloma and meningioma.

"Whether dealing with the lack of access to healthy foods or an overabundance of unhealthy food, there is a critical need to develop additional research that explores the associations between obesity-related cancer mortality and food inequities," Watson and Odoms-Young concluded, adding that the current study "takes an important step in providing strong evidence for research that explores the ethical, legal, and social implications of food inequities."

For their study, Bevel's group used U.S. Department of Agriculture Food Environment Atlas data (from 2012, 2014, 2015, 2017, and 2020) and paired it with CDC mortality data (from 2010-2020) to examine the association between food deserts and swamps with obesity-related cancer mortality. In total, 3,038 of the 3,142 U.S. counties or county equivalents had sufficient information on both for inclusion.

Food-swamp scores were calculated as the ratio of unhealthy food options (fast-food outlets plus convenience stores) to healthy food options (grocery stores plus farmers markets) using a modified Retail Food Environment Index score.

Desert scores were calculated via the Food Environment Atlas, and represented the percentage of each county's residents that were lower income and lived far from a supermarket -- more than a mile away for people living in urban areas and more than 10 miles for those in rural areas. Both scores were divided up into low, moderate, and high based on the total county-level score.

For the initial analysis, the cutoff for high mortality rates from obesity-related cancers was 71.8 deaths or higher per 100,000 population (758 of the counties), which was based on the median of county-level mortality rates.

A greater number of people living in the counties with high mortality from these cancers lived in areas considered food swamps or food deserts when compared with the counties with low obesity-related cancer mortality:

• Food swamps: 19.86% vs 18.20%
• Food deserts: 7.39% vs 5.99%

And counties with high mortality rates included a higher proportion of Black residents (3.26% vs 1.77%), people over 65 years (15.71% vs 15.40%), adults with obesity (33.0% vs 32.1%) or diabetes (12.5% vs 10.7%), along with higher rates of poverty (19.0% vs 14.4%).

In the analysis that looked at mortality rates in tertiles, cutoffs for obesity-related cancer mortality rates were 31-74 per 100,000 (low), 75-82 per 100,000 (moderate), and 83-185.7 per 100,000 (high).

Limitations cited by Bevel's team included the fact that associations between cancer deaths and food environment were made on the county- rather than individual-level, the possible misclassification of some stores, and that race and other socioeconomic data were again assessed on the county level.

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