Vegetarians Have Lower Risk of Multiple Cancers
A comprehensive study involving over 1.8 million individuals tracked over many years has revealed that vegetarians have a substantially lower risk of developing five types of cancer. The research found that vegetarians had a 21% lower risk of pancreatic cancer, a 12% lower risk of prostate cancer, and a 9% lower risk of breast cancer compared to meat eaters. These cancers collectively account for approximately one-fifth of cancer deaths in the UK.
Additionally, vegetarians exhibited a 28% lower risk of kidney cancer and a 31% lower risk of multiple myeloma, according to findings published in the British Journal of Cancer.
Dr Aurora Pérez-Cornago, the principal investigator on the study, which was conducted while she was at the University of Oxford, stated: "This study is really good news for those who follow a vegetarian diet because they have a lower risk of five cancer types, some of which are very prevalent in the population."
Increased Risks for Some Cancers Among Vegetarians and Vegans
Despite the overall protective effect of a vegetarian diet, the study also found that vegetarians had nearly double the risk of developing squamous cell carcinoma, the most common type of oesophageal cancer, compared with meat eaters. The researchers suggested this may be due to deficiencies in key nutrients such as B vitamins among vegetarians.
Furthermore, vegans were found to have a 40% higher risk of bowel cancer compared to meat eaters. This elevated risk may be linked to a lower average intake of calcium (590 mg per day versus the UK recommendation of 700 mg per day) and reduced consumption of other essential nutrients.
Further Research Needed to Clarify Dietary Impacts
The researchers emphasized the need for additional studies to determine whether meat consumption itself poses a risk or if specific components of vegetarian diets contribute to the observed lower cancer risks. They noted that the relationship may differ depending on the cancer type.
Prof Tim Key, emeritus professor of epidemiology at the University of Oxford and co-investigator, commented: "My feeling is the difference is more likely to be due to the meat itself, but that’s an opinion that we haven’t looked at directly."
While the link between red and processed meat consumption and bowel cancer risk is well established, previous research has been limited by the small numbers of vegetarians and vegans included. This study overcame that limitation by pooling data from multiple global studies on diet and health.
Study Population and Methodology
The analysis included approximately 1.64 million meat eaters, 57,016 poultry eaters (excluding red meat), 42,910 pescatarians (fish but no meat), 63,147 vegetarians, and 8,849 vegans, followed for an average of 16 years. The study accounted for factors influencing cancer risk such as body mass index and smoking habits.
Funded by the World Cancer Research Fund, the study investigated 17 different cancer types, including those affecting the gastrointestinal tract, lung, reproductive system, urinary tract, and blood.
Findings on Bowel Cancer and Other Diet Groups
The study found no evidence that vegetarians had a lower risk of bowel cancer compared with meat eaters. This may be due to the relatively low intake of red and processed meat among participants compared to more recent cohorts. Prof Key noted that these findings are "not incompatible" with prior research linking red and processed meat to bowel cancer.
He added, "It could be that if we had had more people with very high intakes of meat in the meat-eating group, the results could have been different."
Regarding other dietary groups, pescatarians showed lower risks of breast, kidney, and bowel cancers. Poultry eaters were found to have a reduced risk of prostate cancer.
Considerations on Dietary Changes Over Time
Participants were followed for an average of 16 years, allowing effective tracking of cancer outcomes. However, dietary patterns have evolved since the 1990s and 2000s when many participants were recruited. For example, consumption of ultra-processed foods has increased, and vegan products like oat milk are now often fortified with calcium and other nutrients.
Expert Commentary
Prof Jules Griffin, director of the Rowett Institute at the University of Aberdeen, who was not involved in the study, remarked: "What is missing in this study is a comparison to a group eating the NHS Eatwell guidelines, where meat and fish consumption is in moderation, but at the same time provides important nutrients to the diet – this may be the optimum diet for reducing risk in the population for diet associated cancer."
