Digestive System Cancers Have Risen 2-Fold Worldwide: Poor Diet Is to Blame

A new study found that more than 1 in every 5 new gastrointestinal (GI) cancer cases worldwide is associated with poor diet.

Research by Dr. Li Liu and colleagues from the Department of Epidemiology and Biostatistics, School of Public Health, Tongji Medical College, Huazhong University of Science and Technology in China, was published in November 2024 in Gastroenterology. The study identified excessive processed meat consumption (the largest contributor), insufficient fruit consumption and low whole-grain intake as the most important dietary risk factors. It also reported that the number of diet-related GI cancer cases between 1990 and 2018 had doubled.

Dr. Liu said: "Policy interventions such as taxing unhealthy foods and subsidizing nutritious options could reduce cancer risk by changing eating habits."

The Link Between Diet and Gastrointestinal Cancers

The research team examined data on 6 major GI cancers, including colorectal, liver, esophageal, pancreatic, gallbladder and biliary tract cancers, in 184 countries over 1990-2018. Over the past 30 years, age-standardized incidence rates, or annual new case rates, for liver, pancreatic and colorectal cancers increased substantially.

The effect of diet was assessed independently of energy intake and obesity using a comparative risk assessment model to evaluate its contribution to GI cancers. Overall, excessive processed meat consumption and insufficient fruit and whole-grain intake accounted for 66.51% of diet-related GI cancer cases in 2018. Average processed meat consumption worldwide was 17 grams daily in 2018, falling to as little as 3 grams in South Asia.

In addition, diet-related cancer incidence was positively correlated with the Sociodemographic Index (SDI), which incorporates a country's level of development, income and fertility rates:

The highest GI cancer rates were found in Central and Eastern Europe, Central Asia, Latin America and the Caribbean, and high-income countries.

These findings suggest that regional public health policies should focus on dietary interventions to reduce cancer rates.

Striking Figures

• In 2018, 21.5% of all GI cancer cases worldwide (confidence interval [CI]: 19.1%-24.5%) were associated with poor diet. This proportion was 22.4% in 1990 (CI: 19.7%-25.6%), meaning it remained relatively stable over 30 years.
• The absolute number of diet-related cancer cases rose from 580,862 (CI: 510,658-664,076) in 1990 to 1,039,877 (CI: 923,482-1,187,244) in 2018.
• The leading dietary risk factors in 2018 were:
  • Excessive processed meat consumption (5.9%; CI: 4.2%-7.9%)
  • Insufficient fruit consumption (4.8%; CI: 3.8%-5.9%)
  • Insufficient whole-grain consumption (3.6%; CI: 2.8%-5.1%)
  • A notable change since 1990: the third-largest risk factor in 1990 was insufficient non-starchy vegetable intake, but insufficient whole-grain intake has since taken its place.

Dr. Liu said: "The link between diet and GI cancers is already well established. However, the dramatic doubling of diet-related cases over recent decades was unexpected."

Liu noted that this increase was largely due to global population growth and aging. "Although aging is inevitable, we can reduce the burden of diet-related GI cancers by focusing on modifiable behaviors, particularly through targeted dietary interventions," Liu added.

Diet: A Modifiable Risk Factor

Although the mechanisms underlying this association are not fully understood, substantial evidence suggests that diet can alter the gut microbiome and thereby promote cancer development.

Regional Differences and Priority Areas for Intervention

According to the study, Central and Eastern Europe, Central Asia, Latin America and the Caribbean, and high-income countries had the highest diet-related GI cancer burden in 2018 . This burden was found to be largely associated with increased processed meat consumption.

• In 1990, the highest proportion of diet-related GI cancers was in Central and Eastern Europe and Central Asia (31.6%; CI: 27.0%-37.4%).
• These regions also had the highest proportion in 2018 (31.6%; CI: 27.3%-36.5%).

The researchers reported a higher burden of diet-related GI cancer in countries with higher SDI levels and among more educated, urban populations. The main reason was the greater prevalence of processed meat consumption in these countries.

Although the team confirmed the association between diet and GI cancers, it emphasized the need for more basic research to fully understand how diet triggers these cancers.

Conclusion: Urgent Public Health Interventions Are Needed!

These findings underline the urgent need for more proactive public health policies to reduce GI cancer risk.

Diet is a modifiable risk factor, and there is still considerable room for improvement. Particular attention should be given to strategies that reduce processed meat consumption and increase whole-grain and fruit intake.