Suboptimal Diets Tied to Global Doubling of GI Cancers

More than 1 in 5 of new gastrointestinal (GI) cancer cases globally were attributable to suboptimal dietary intake, according to a recent study.

Writing in Gastroenterology, researchers led by Li Liu, PhD, of the Department of Epidemiology and Biostatistics, Ministry of Education Key Lab of Environment and Health, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology in Wuhan, China, reported that excessive consumption of processed meats (the biggest culprit), insufficient fruit intake, and insufficient whole grain intake were the leading dietary risk factors. In addition, the number of diet-related cases doubled from 1990 to 2018.

“In regions with limited access to healthy foods, policy interventions like taxing unhealthy foods and subsidizing nutritious options may help shift dietary patterns and reduce cancer risk,” Liu said in an interview.

The study examined meta-analyses from 184 countries in seven regions for the period 1990-2018 looking at rates of six major GI cancers: Colorectal, liver, esophageal, pancreatic, and gallbladder/biliary tract. Among these, the age-standardized incidence of liver, pancreatic, and colorectal increased significantly over the past three decades.

The research team used a comparative risk assessment model to estimate the impact of diet on GI cancer independent of energy intake and adiposity. Although the principal dietary risk factors varied across individual cancers, suboptimal intake of the three aforementioned components was responsible for 66.51% of all diet-attributable GI cancers in 2018. The global mean processed meat consumption was 17 g/d in 2018, falling to a low in South Asia of 3 g/d.

The investigators also found diet-linked cancer incidence positively correlated with the Sociodemographic Index (SDI), an integrated measure of national development, income, and fertility. Incidence varied across world regions, with the highest proportion of cases in Central and Eastern Europe, Central Asia, Latin America, the Caribbean, and in high-income countries. The findings support the development of targeted diet-related public health interventions in various regions and nations to reduce GI cancer incidence, the authors wrote.

Among the study’s specific findings:

• In 2018, 21.5% (95% uncertainty interval [UI], 19.1-24.5) of incident GI cancer cases globally were attributable to suboptimal diets, a relatively stable proportion since 1990 (22.4%, 19.7–25.6).
• Absolute diet-attributable cases doubled from 580,862 (UI, 510,658-664,076) in 1990 to 1,039,877 (UI, 923,482-1,187,244) in 2018.
• Excessive processed meat consumption (5.9%; UI, 4.2-7.9), insufficient fruit intake (4.8%; UI, 3.8-5.9), and insufficient whole grain intake (3.6%; UI, 2.8-5.1) were the most significant dietary risk factors in 2018 — a shift from 1990 when the third major concern was insufficient non-starchy vegetable intake.

Given the well-established link between diet and GI cancers, the incidence findings came as no surprise. “However, the dramatic doubling of diet-attributable cases over the past few decades was truly unexpected,” Liu said. “This increase can likely be attributed to global population growth and aging. While aging is an irreversible process, we can still reduce the growing burden of diet-related GI cancers by focusing on modifiable behaviors, particularly through targeted dietary interventions.”

A Modifiable Risk Factor

Commenting on the analysis but not involved in it, Andrew T. Chan, MD, MPH, a professor of medicine at Harvard Medical School and a gastroenterologist at Massachusetts General Hospital, both in Boston, noted that his own group’s studies also support the association of diet with an increased risk for GI cancers, particularly colorectal cancers.

“Although much work needs to be done to clarify the precise mechanisms underlying this association, there are substantial data that diet may cause changes in the gut microbiome, which in turn promotes cancer,” Chan said in an interview. “Going forward, we are working to develop strategies in which diet is modified to mitigate the risk of cancer associated with suboptimal diets.”

In other study findings, Liu’s group observed that two regional groups, Central and Eastern Europe, Central Asia, Latin America, and the Caribbean, as well as high-income countries, bore the top three diet-attributable burdens worldwide in 2018, all driven mostly by an upward-trending excess of processed meat.

By regions, Central and Eastern Europe and Central Asia experienced the highest attributable burden across regions in 1990 (31.6%; UI, 27.0-37.4) and 2018 (31.6%; UI, 27.3-36.5).

As for the impact of the SDI, the authors explained that diet-attributable GI cancer burden was higher among adults with higher education and living in urban areas than among those with lower education and rural residency. “Some dietary habits tended to be worse in higher-SDI countries, specifically, higher consumption of processed meats,” they wrote.

Although the proportional attributable GI incidence remains relatively stable, they added, the doubling of absolute cases from 1990 to 2018, along with the discrepancies between urbanicity and countries/regions, supports more targeted preventive measures.

And while the diet-GI cancer connection is clear, they agreed with Chan in that “the precise pathogenesis from suboptimal diets to these cancers remains unclear and requires further basic studies to clarify the mechanism.”

In the meantime, the findings “underscore the urgent need for proactive public health interventions. Diet, as a modifiable risk factor, still offers substantial potential for improvement,” Liu said.

This study was funded by the National Natural Science Foundation of China and the American Cancer Society.

The authors and Chan disclosed no relevant conflicts of interest.

Diana Swift is an independent medical journalist based in Toronto, Canada.