Reducing meat consumption may lower the risk of several common cancers, but the relationship is more complex than previously understood. A large-scale analysis of diet and cancer indicates a lower risk for five major tumor types, even as also raising questions about colorectal cancer, a disease frequently linked to meat consumption. The study, coordinated by the University of Oxford in the United Kingdom and funded by the World Cancer Research Fund, included data from over 1.8 million people across nine prospective cohorts in the United Kingdom, the United States, Taiwan, and India, followed for an average of 16 years. During this period, over 220,000 new cancer cases emerged, according to Hotnews.
Published in the British Journal of Cancer, the results showed that vegetarians had a 21% lower risk of pancreatic cancer, a 12% lower risk of prostate cancer, a 9% lower risk of breast cancer, a 28% lower risk of kidney cancer, and a 31% lower risk of multiple myeloma compared to those who eat meat. These five cancers collectively account for approximately one-fifth of cancer deaths in Western countries. The research also found that vegetarians had nearly double the risk of squamous cell esophageal cancer.
The data came from cohorts including EPIC-Oxford, Adventist Health Study-2, UK Biobank, Million Women Study, and NIH-AARP Diet and Health Study – some of the largest epidemiological studies in the world, tracking the long-term health and lifestyle of highly large populations. Researchers accounted for factors that could skew the results, such as body weight, smoking, alcohol consumption, physical activity, diabetes, and adjusted the calculations accordingly.
Compared to meat-eaters, vegetarians had a hazard ratio (HR) of 0.79 for pancreatic cancer, 0.91 for breast cancer, 0.88 for prostate cancer, 0.72 for kidney cancer, and 0.69 for multiple myeloma. In this type of analysis, any value below 1 indicates a lower risk compared to the reference group. Those who consumed fish also showed lower risks: a 15% lower risk of colorectal cancer, a 7% lower risk of breast cancer, and a 27% lower risk of kidney cancer. Individuals who ate only poultry – excluding red meat – had a 7% lower risk of prostate cancer.
The study is observational, meaning it cannot prove a direct cause-and-effect relationship. “My feeling is that the differences are more likely related to the meat itself rather than simply the fact that vegetarians eat healthier foods. But that’s an opinion I haven’t tested directly,” explained Tim Key, professor emeritus of epidemiology at the University of Oxford and one of the study’s authors.
Previous studies have indicated that vegetarians in Western Europe and North America tend to consume less saturated fat, more fiber, and have a lower body weight than those who include meat in their diet. These factors could contribute to a reduced cancer risk. However, researchers adjusted for body weight, so differences in weight do not fully explain the observed association.
Researchers also considered the role of IGF-I (insulin-like growth factor 1). People who consume fewer animal proteins tend to have lower levels of this hormone, and higher IGF-I concentrations have been linked to an increased risk of prostate cancer in multiple studies.
One finding that drew researchers’ attention was that vegetarians had a nearly two-fold (HR 1.93) increased risk of squamous cell esophageal carcinoma compared to meat-eaters. The analysis was based on 31 cases identified in three UK cohorts. While the number is small, the association remained stable even after excluding the first four years of follow-up and limiting the analysis to non-smokers. Researchers suggest nutritional deficiencies may play a role, specifically riboflavin (vitamin B2) and zinc, both abundant in animal products, appear to have a protective effect on the esophagus. Areas with the highest rates of esophageal cancer globally (northeast Iran, Linxian and Cixian in China) are those with restrictive diets and low animal protein intake.
While the International Agency for Research on Cancer (IARC) and the World Cancer Research Fund (WCRF) have established that the risk of colorectal cancer increases among consumers of processed meat and, likely, red meat, the new study observed that this link is not conclusive. Specifically, researchers identified a lower risk of this type of cancer among vegetarians who also consume fish, but a higher risk for vegans (40%).
However, the authors caution that this result should be interpreted with caution. The observation of a higher risk of colorectal cancer among vegans was based on a small number of cases and was no longer statistically significant after excluding the first years of follow-up. Researchers say these results do not support the idea that the absence of meat increases risk, but may reflect other nutritional factors, such as a lower calcium intake. Average calcium intake among vegans was only 590 mg per day, below the recommended level of 700 mg/day. Previous studies have linked dairy products and calcium supplements to a lower risk of colorectal cancer.
the study does not refute existing evidence regarding the unfavorable effect of processed meat and, likely, red meat on the risk of colorectal cancer, but suggests that the relationship is more nuanced and may depend on the amounts consumed and the overall diet.
Amy Hirst, a health information manager at Cancer Research UK, said the study is “high quality” but emphasized that the results are not strong enough to draw definitive conclusions. “More research is needed on larger and more diverse populations to better understand these patterns and their causes. When it comes to reducing cancer risk, maintaining a healthy and balanced diet overall matters more than individual foods consumed,” the specialist cautioned.
Professor Jules Griffin, director of the Rowett Institute at the University of Aberdeen, Scotland, who was not involved in the research, considers the study impressive but says the analysis does not include a group of people following the recommendations of the NHS Eatwell guide (the official UK public health system’s dietary guidelines), where meat and fish consumption is moderate, and the diet provides adequate nutrients. In his opinion, such a dietary pattern could represent the most appropriate option for reducing diet-related cancer risk in the general population.
As with any observational research, this study has limitations that the authors acknowledge. Participants’ diets were assessed only once, at the beginning of the study, and eating habits have since changed. Consumption of ultra-processed foods has increased dramatically, and vegan products like oat milk, for example, are usually fortified with calcium and vitamins. Results from the 1990s and 2000s may not accurately reflect today’s reality.
The number of vegans in the study was small (8,849), so any conclusions about vegans should be viewed with caution. The study also could not distinguish between a vegetarian diet based on vegetables, fruits, and whole grains and one based on refined carbohydrates or ultra-processed foods. There is also no data on how the foods were prepared.
