Vegetarian diets linked to higher risk of esophageal squamous cell carcinoma

While plant-based diets were linked to lower risks of a number of cancers, vegetarian diets were also associated with a higher risk of esophageal squamous cell carcinoma (ESCC), according to a study published in the British Journal of Cancer in February 2026.

Vegetarian and vegan diets are widely considered healthy eating patterns and are typically linked to lower risks of heart disease, obesity and many cancers. These diets exclude meat and fish, and vegan diets also avoid dairy products and eggs. When carefully planned, they can provide ample nutrition and are usually higher in fiber, carotenoids and vitamin C while containing less saturated fat.

However, these eating patterns can result in lower intake of certain nutrients such as protein, vitamin B12 and calcium, which could potentially lead to illness or cancers including ESCC—a type of esophageal cancer that starts in the flat, thin cells lining the upper and middle parts of the esophagus. It can grow into nearby tissues and sometimes spread to other parts of the body, making early detection and treatment important.

Due to this, researchers are still working to understand how these nutritional differences may influence cancer risk.

To explore this space, investigators at the University of Oxford formed the Cancer Risk in Vegetarians Consortium, which grabbed individual level data from nine large prospective cohort studies across several regions. The project represents the most comprehensive analysis to date examining plant-based diets and cancer risk. While the results suggested protective associations for some cancers, the analysis also identified a higher risk of ESCC among vegetarians, highlighting a potential concern that pushes on further study.

Researchers looked at pooled data from participants in the United States, the United Kingdom, Taiwan and South Asia. Diet information was collected using food frequency questionnaires, and participants were categorized as meat eaters, poultry eaters, pescatarians, vegetarians or vegans. Cancer diagnoses were identified through national cancer registries and medical records. Statistical models were then used to compare cancer risk across diet groups while adjusting for several non dietary factors including smoking, body mass index, alcohol use and physical activity.

The analysis included data from more than 1.8 million participants across the nine studies. Most participants were meat eaters, while smaller groups followed poultry based, pescatarian, vegetarian or vegan diets. Recruitment for the cohorts occurred between 1980 and 2010. Follow up ranged from 6 to 27 years depending on the study.

During this time, researchers found more than 220,000 cases of cancer across multiple organ systems. One of the most notable findings involved ESCC. Compared with meat eaters, vegetarians had a significantly higher risk of ESCC, with a hazard ratio of 1.93. The association remained significant in sensitivity analyses that excluded the first four years of follow up and when the analysis was limited to participants who had never smoked.

Researchers said this consistency suggests the finding was unlikely to be explained by smoking or other early health changes. Although the number of ESCC cases among vegetarians was relatively small, the magnitude of the association drew attention to possible nutritional or metabolic explanations.

The study also identified several lower cancer risks in certain diet groups. Pescatarian diets were associated with lower risks of colorectal cancer and kidney cancer compared with meat eating diets. Vegetarians had lower risks of pancreatic cancer, kidney cancer and multiple myeloma. Breast cancer risk was also slightly lower among pescatarians and vegetarians, particularly in postmenopausal women. However, investigators noted that some of these associations were partly explained by differences in body mass index between diet groups.

Researchers suggested that the elevated ESCC risk among vegetarians could be related to lower intake of specific nutrients that are more abundant in animal foods. Previous studies have linked deficiencies in nutrients such as riboflavin and zinc with higher rates of esophageal squamous cell carcinoma in certain regions of the world. Vegetarians and vegans may also have lower intake of protein, vitamin B12 and long chain omega 3 fatty acids depending on dietary choices.

The authors stressed that vegetarian diets are defined by the absence of certain foods rather than the specific healthy foods. As a result, the nutritional quality of plant-based diets can vary widely. Some individuals could consume diets rich in whole grains, fruits and vegetables while others may rely more heavily on refined carbohydrates and processed foods.

The study has several strengths: by monitoring data from multiple cohorts, the consortium was able to analyze more than 1.8 million participants and examine rare cancers such as ESCC. The long follow up period and standardized statistical methods also improved the reliability of comparisons across diet groups.

However, several limitations should be considered. The number of ESCC cases among vegetarians was still relatively small and the number of cancer cases among vegans was limited, reducing statistical power for some analyses. Diet information was self-reported at baseline and may have changed over time. Researchers also lacked detailed information on food processing methods and long-term adherence to diet patterns.

The authors stated that further research is needed to better understand the biological pathways linking diet and esophageal cancer risk. Future studies should examine the role of metabolic factors and potential nutrient deficiencies and should include more diverse populations and larger numbers of vegan participants.