Vegetarian diet linked to lower risk of five major cancers, study finds

The study was led by researchers at Oxford Population Health’s Cancer Epidemiology Unit and funded by World Cancer Research Fund which supports global scientific research on cancer prevention and survival through diet, weight and physical activity. It is published today in the British Journal of Cancer. 

Appropriately planned vegetarian diets are considered to be healthy but there has been uncertainty about how these diets influence the risk of specific cancers, largely because individual studies do not include enough vegetarians, reads the Oxford Population Health website.

To address these questions, the researchers pooled data from more than 1.8 million people from three continents through the Cancer Risk in Vegetarians Consortium.

They compared the risk of 17 different cancers across five diet groups: meat eaters, poultry eaters (do not eat red or processed meat), pescatarians (fish eaters), vegetarians (eat dairy and/or eggs), and vegans.

Compared with meat eaters, vegetarians had:

21% lower risk of pancreatic cancer

9% lower risk of breast cancer

12% lower risk of prostate cancer

28% lower risk of kidney cancer

31% lower risk of multiple myeloma.

However, vegetarians had:

Nearly double the risk of squamous cell carcinoma of the oesophagus.

There were no statistically significant differences in risk for colorectal, stomach, liver, lung (in never smokers), endometrial, ovarian, mouth and pharynx, or bladder cancers, or non-Hodgkin lymphoma, leukaemia, and oesophageal adenocarcinoma in vegetarians.

Tim Key, Emeritus Professor of Epidemiology at Oxford Population Health, and co-investigator of the study said, "There are around 3 million vegetarians in the UK, with interest in vegetarianism growing in many parts of the world."

Cancer is a leading cause of death worldwide, accounting for nearly one in six deaths.

Dietary patterns that prioritise fruit, vegetables, and fibre-containing foods, and avoid processed meat, are recommended to reduce cancer risk. Our study helps to shed light on the benefits and risks associated with vegetarian diets.’

Vegans had a statistically significant higher risk of colorectal (bowel) cancer when compared with meat eaters.

For the other cancers studied, there was no evidence that risk in vegans differed from meat eaters, and for some less common cancers there were too few vegan cases to analyse. Further studies are needed to confirm these results in the vegan population.

Aurora Perez Cornago, principal investigator of the study and formerly Associate Professor at Oxford Population Health, added "Vegetarians typically consume more fruit, vegetables and fibre than meat eaters and no processed meat, which may contribute to lower risks of some cancers. The higher risk of oesophageal squamous cell carcinoma in vegetarians and bowel cancer in vegans 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."

Pescatarians had lower risks of breast and kidney cancers, as well as a lower risk of bowel cancer. Poultry eaters were found to have a lower risk of prostate cancer.

Yashvee Dunneram, first author of the study, and former postdoctoral epidemiologist at Oxford Population Health, said, "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. Moreover, 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."

Dr Helen Croker, Assistant Director of Research and Policy at World Cancer Research Fund International, said, "We funded this research because people deserve evidence they can trust as they consider eating less meat and this study provides the most comprehensive evidence yet on vegetarian and non-meat diets and cancer risk. The results suggest non-meat diets are linked to lower risks for some cancers, though not all, highlighting important differences between cancer types and the role of different dietary patterns."

"To increase your overall protection from cancer, our advice is to build meals around wholegrains, pulses, fruit and vegetables, and avoid processed meat and limit red meat."