Vegetarian Diets May Raise Cancer Risk in Some Groups, Study Finds

A new study challenges the assumption that vegetarian diets always reduce cancer risk. Published in the British Journal of Cancer on 23 June 2026, the research by N.K. Shah highlights unexpected findings about certain vegetarian populations and their susceptibility to esophageal and colorectal cancers. The study revealed that some vegetarian groups face a higher risk of specific esophageal and colorectal cancers. This paradox appears linked to multiple factors, including microbial dysbiosis. In affected patients, protective gut bacteria were depleted, while harmful, pro-inflammatory and genotoxic species were overrepresented.

Genetic predispositions also play a role. Variants in genes tied to folate metabolism, DNA methylation, and immune regulation may interact with vegetarian diets to increase cancer risk. Additionally, high-heat cooking methods used in some vegetarian cuisines can produce carcinogens like polycyclic aromatic hydrocarbons and heterocyclic amines.

Not all plant-based diets offer the same protection. Those heavy in processed foods or lacking essential micronutrients can weaken the gut lining and promote cancer development. The study even found distinct molecular signatures in vegetarians with these cancers, pointing to harmful tissue changes and mutagenic activity in the digestive tract.

Dietary habits also influenced outcomes. Pescatarians showed lower cancer rates than strict vegans, possibly due to better nutrient intake supporting gut defences. The research calls for personalised dietary advice to ensure vegetarian diets include all necessary nutrients. It also recommends adapting cancer screening programmes to account for dietary patterns, enabling earlier detection in at-risk groups. These steps aim to address the elevated cancer risks observed in certain vegetarian populations.