Vegetarian diets are linked to a lower risk of several cancers, including breast, prostate, kidney, pancreatic and multiple myeloma, but also to an increased risk of a rare form of esophageal cancer, according to the largest study of its kind. The research, published today in the British Journal of Cancer, analyzed data from over 1.8 million people across three continents.
The study, led by researchers at Oxford Population Health’s Cancer Epidemiology Unit and funded by World Cancer Research Fund, compared cancer risks across five dietary groups: meat eaters, poultry eaters (those who avoid red and processed meat), pescatarians (fish eaters), vegetarians (who consume dairy and/or eggs), and vegans.
Compared to meat eaters, vegetarians demonstrated a 21% lower risk of pancreatic cancer, a 9% lower risk of breast cancer, a 12% lower risk of prostate cancer, a 28% lower risk of kidney cancer, and a 31% lower risk of multiple myeloma, the study found.
However, vegetarians had nearly double the risk of squamous cell carcinoma of the esophagus, a rare cancer of the food pipe. Vegans, meanwhile, showed a statistically significant higher risk of colorectal cancer compared to meat eaters. For other cancers studied, there was no evidence of differing risk between vegans and meat eaters, though researchers noted limited data for some less common cancers.
“There are around 3 million vegetarians in the UK, with interest in vegetarianism growing in many parts of the world,” said Tim Key, Emeritus Professor of Epidemiology at Oxford Population Health and a co-investigator of the study. “Cancer is a leading cause of death worldwide, accounting for nearly one in six deaths. Our study helps to shed light on the benefits and risks associated with vegetarian diets.”
Pescatarians exhibited lower risks of breast and kidney cancers, as well as bowel cancer. Poultry eaters were found to have a lower risk of prostate cancer.
Researchers cautioned that the numbers of cases for some cancers within the vegetarian and vegan groups were relatively small, limiting the certainty of some findings. They also highlighted the variability in nutrient intake and overall diet quality among vegetarians.
“Among the 72,000 vegetarians and vegans included in our study, the numbers of cases for some cancers were small, which limits the certainty of some findings,” explained Yashvee Dunneram, first author of the study and former postdoctoral epidemiologist at Oxford Population Health. “nutrient intakes and overall diet quality vary substantially within and between vegetarian populations. Our next challenge is to collect more data on vegan diets and more data from other parts of the world.”
Aurora Perez Cornago, principal investigator of the study, suggested the lower cancer risks among vegetarians may be linked to higher consumption of fruits, vegetables, and fiber, and the avoidance of processed meat. The increased risk of esophageal squamous cell carcinoma in vegetarians and bowel cancer in vegans, she added, “may relate to lower intakes of certain nutrients more abundant in animal foods. Additional research is needed to understand what is driving the differences in cancer risk found in our study.”
Dr. Helen Croker, Assistant Director of Research and Policy at World Cancer Research Fund International, stated the study provides the most comprehensive evidence to date on the relationship between non-meat diets and cancer risk. She reiterated the organization’s advice to build meals around wholegrains, pulses, fruit and vegetables, and to avoid processed meat and limit red meat consumption.
