Following a vegetarian diet is associated with a reduced risk of several cancers, but a new large-scale study reveals a surprising link to an increased risk of one specific type of esophageal cancer. Understanding these nuanced connections between diet and cancer risk is a growing area of public health research.
The research, led by Yashvee Dunneram at the University of Oxford’s Cancer Epidemiology Unit in the United Kingdom, analyzed data from nearly 1.8 million individuals across three continents. The findings, published in 2026 in the British Journal of Cancer, offer the most comprehensive glance to date at the relationship between vegetarian diets and cancer incidence.
Study Details
Researchers harmonized data from nine cohort studies conducted in the United Kingdom, the United States, Taiwan, and India, encompassing a total of 1,817,477 participants. These participants were categorized into five dietary groups: 1,645,555 meat-eaters, 57,016 poultry eaters, 42,910 pescatarians, 63,147 vegetarians, and 8,849 vegans. To be included in the study, participants had to be at least 15 years ancient, have no prior history of cancer (excluding basal cell carcinoma), provide reliable dietary information, and have plausible energy intakes (ranging from 2,092-14,644 kJ/day for women and 3,347-16,736 kJ/day for men). The study followed participants for a median of 16 years, tracking 220,387 cases of cancer through cancer registries and combined methods.
Dietary groups were defined based on cohort-specific questionnaires, ranging from 16 to 217 questions, focusing on consumption of red/processed meat, poultry, fish, dairy, and eggs over the past 12 months. Meat-eaters consumed red or processed meat, poultry eaters consumed poultry but not red meat, pescatarians ate fish but no meat or poultry, vegetarians included dairy and eggs but excluded meat or fish, and vegans avoided all animal products.
Compared to meat-eaters, vegetarians demonstrated a 21% lower risk of pancreatic cancer (HR 0.79. 95%CI 0.65-0.97), even as pescatarians showed an 85% lower risk of colorectal cancer (HR 0.85; 95%CI 0.77-0.93). Conversely, vegans had a 40% higher risk of colorectal cancer (HR 1.40; 95%CI 1.12-1.75). Vegetarians similarly faced an almost doubled risk of esophageal squamous cell carcinoma (HR 1.93; 95%BI 1.30-2.87).
Lower Risk of Multiple Myeloma
Poultry eaters had a slightly lower risk of prostate cancer (HR 0.93; 95%CI 0.88-0.98), while fish eaters and vegetarians both showed a 7% lower risk of breast cancer (HR 0.93; 95%CI 0.88-0.98, and HR 0.91; 95%CI 0.86-0.97, respectively), particularly after menopause. Vegetarians also exhibited a 31% lower risk of multiple myeloma (HR 0.69; 95%CI 0.51-0.93). Pescatarians and vegetarians also had lower risks of kidney cancer (HR 0.73; 95%CI 0.58-0.93 and HR 0.72; 95%CI 0.57-0.92, respectively). No significant differences were observed for bladder cancer, non-Hodgkin lymphoma, leukemia, or lung cancer among never-smokers.
The study suggests that plant-based diets may offer protection against certain cancers due to higher intakes of fiber, carotenoids, and vitamin C, and/or lower consumption of animal proteins. Researchers suggest that balanced vegetarian diets are advisable, but with attention to potential deficiencies in nutrients like B12, calcium, riboflavin, and zinc, which could contribute to the increased risk of esophageal or colorectal cancer in vegans. This research highlights the importance of carefully planned diets for optimal health outcomes.
