The United States has 19 million people living in food deserts. This is where they have less access to nutritious and healthy food. More than 32 million people are below the poverty line, which means they have limited choices and can only eat the cheapest food. Numerous studies have shown that diet plays a significant role in early mortality and the development and progression of chronic diseases like heart disease, type 2 diabetes, and cancer.
Researchers are only beginning to understand the complex interplay between individual and community characteristics and diet and health. A multidisciplinary team of researchers from Stanford University, University of Washington, and Stanford University conducted the largest ever nationwide study on the relationship between food environments, demographics, and dietary quality in the United States. This was done with the help of a popular app for food journaling that uses smartphones. The results of this five-year effort were published Jan. 18. Nature CommunicationsThis should provide scientists, policymakers, and health care professionals with plenty to think about.
“Our findings show that higher access to grocery shops, lower access to fast foods, higher income, and college education are independently associated to higher consumption of fresh fruits, vegetables, lower intake of fast food, and less likelihood to be classified as overweight or obese,” said lead author Tim Althoff, UW assistant professor at the Paul G. Allen school of Computer Science & Engineering.
Althoff stated that these results were not surprising and that they are challenging because of the small sample sizes and single locations used in studies. Also, there is a non-uniform design and inconsistent design across studies. Our quasi-experimental method allowed us to study the effects on a large scale and identify which factors are most important, something that is not possible with traditional epidemiological studies.
Althoff was a doctoral candidate at Stanford when the study began. It analyzed data from more then 1.1 million MyFitnessPal app users -; which covered approximately 2.3 Billion food entries and encompassed more than 9,800 U.S. Zip codes – to gain insights into how factors, such as access to fast food and grocery stores, education level, and family income, affect people’s food consumption, and overall dietary health.
The team calculated the association between these variables from data by zip code. This was done using four self-reported dietary outcomes recorded between 2010 and 2016. These were fresh fruit and vegetables, fast food consumption and soda consumption. Also, the incidence of being overweight or obese as determined by body mass index.
The researchers used a matching-based approach to determine how each variable correlated with these outcomes. They divided the zip codes into treatment and controls groups, and then split them along the median for each input. This allowed them to compare app logs from zip codes statistically above the median, such as those with more than 20% of the population living within a half-mile of the nearest grocery shop -; with those below it.
The greatest predictor of a healthier diet was higher educational attainment, which was 29.8% or greater of the population with a college education. All four inputs had positive effects on dietary outcomes. However, a slightly higher percentage of overweight or obese people were associated with high family income. This is defined as income at or above $70,000.241. These results are only a small part of a complex issue that can vary from one community to the next.
“When we dug deeper into the data, we discovered significant differences in how food environment and socioeconomic factors corresponded to dietary health across subpopulations,” said Hamed Nilforoshan (a Stanford doctoral student).
Nilforoshan cited the example of a significantly higher association between above-median grocery shop access and increased fruit-and-vegetable consumption in zip codes with a majority Black residents at a 10.2% difference and with a majority of Hispanic residents at a 7.4% change, compared with zip codes with a majority non-Hispanic, White residents where researchers found only 1.7% difference in the association between increased vegetable consumption and access grocery stores.
“People believe that eliminating food deserts will result in healthier eating. They also believe that higher income and higher education will lead to a better diet. These assumptions are supported by the data at the entire population level,” Jenna Hua, coauthor and founder of Million Marker Wellness, Inc., said. Diet is a complicated issue!
Hua added: “While policies aimed to improve food access, economic opportunities, and education can and will support healthy eating, our findings strongly indicate that we must tailor interventions to communities, rather than following an all-encompassing approach.”
Althoff said that the team’s approach to the topic and its findings can help guide future research. This complex topic has implications for individuals as well as entire communities.
Althoff, who is also the director for the Behavioral Data Science group, said that the study would have an impact on public health and epidemiological research methods. “In terms of the first, we showed that the growing volume and variety consumer-reported data on health can be used for public health research at unprecedented scales and granularity. The latter is where we see many opportunities for future research. We can investigate the mechanisms behind the disparate diet relations across subpopulations of the U.S.
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Journal reference:
Althoff, T., et.(2022) Large-scale diet monitoring data reveal inconsistent associations between diet and food environment. Nature Communications. doi.org/10.1038/s41467-021-27522-y.