Vegetarian Diet and Cancer Risk: A Complex Relationship
A recent landmark study has revealed that a vegetarian diet may help protect against five types of cancer, but it also comes with an increased risk of oesophageal cancer. This research, based on data from over 1.8 million people, highlights the nuanced relationship between diet and cancer risk, showing both benefits and potential drawbacks.
Benefits of a Vegetarian Diet
The study found that vegetarians were up to 31% less likely to develop pancreatic, prostate, breast, kidney cancers, and multiple myeloma compared to meat-eaters. These cancers account for around a fifth of cancer deaths in the UK. For instance:
- Pancreatic Cancer: Vegetarians had a 21% lower risk.
- Breast Cancer: Vegetarians were 9% less likely to develop it, while pescatarians had a 7% lower risk.
- Prostate Cancer: Vegetarians had a 12% lower risk, and pescatarians had a 10% lower risk.
- Kidney Cancer: Vegetarians had a 28% lower risk.
- Multiple Myeloma: Vegetarians had a 31% lower risk.
These findings suggest that a diet rich in fruits, vegetables, and fiber can offer protective benefits against certain cancers.
Risks Associated with a Vegetarian Diet
However, the study also highlighted some risks. Vegetarians were found to have a 93% higher risk of developing the most common type of oesophageal cancer. Vegans, in particular, were more likely to be diagnosed with bowel cancer. This indicates that while vegetarian diets may reduce the risk of some cancers, they might increase the risk of others.
Oesophageal Cancer: A Growing Concern
Oesophageal cancer affects the food pipe and is often associated with symptoms like difficulty swallowing, indigestion, and unexplained weight loss. The study found that cutting out meat and fish nearly doubled the risk of this cancer. Experts suggested that essential nutrients found in red meat, such as iron, zinc, and B vitamins, might play a role in reducing this risk.
Interestingly, participants who limited their red meat intake but still ate poultry were 36% more likely to develop squamous cell carcinoma of the oesophagus compared to red-meat-eaters. This points to the potential protective effect of haem iron found in red meat.
Bowel Cancer: A Double-Edged Sword
At the other end of the digestive tract, bowel cancer is another area of concern. Around 44,000 people are diagnosed with bowel cancer in the UK each year, making it the fourth most common cancer. While a diet high in ultra-processed foods and low in fibre increases the risk, the study found that vegans were 40% more likely to develop bowel cancer than meat-eaters.
This finding underscores the importance of adequate calcium intake, which has been shown to reduce the risk of bowel cancer. Modern well-planned vegan diets can meet this need, but careful planning is essential.
Pancreatic Cancer: A Silent Killer
Vegetarians were 21% less likely to develop pancreatic cancer, one of the deadliest forms of the disease. The pancreas produces hormones to aid digestion and convert sugar into energy. Excess body fat, especially around the abdomen, can lead to insulin resistance, potentially increasing the risk of pancreatic cancer.
There is also evidence that eating a lot of red and processed meat may raise the risk of pancreatic cancer due to the formation of nitrosamines upon cooking.
Lower Risk of Breast and Prostate Cancer
A vegetarian diet was also linked to a lower risk of breast and prostate cancer. Women who followed a vegetarian diet were 9% less likely to develop breast cancer, while men had a 12% lower risk of prostate cancer. Poultry eaters had a lower risk of prostate cancer, and pescatarians had a lower risk of breast cancer.
Additives used to cure bacon have been shown to increase prostate cancer risk by a third, according to research published in the British Medical Journal.
Blood and Kidney Cancers: Protective Effects
Vegetarians had a 28% lower risk of kidney cancer and a 31% lower risk of multiple myeloma, a type of blood cancer. This may be due to lower levels of protein in the blood, which has been linked to kidney damage. Circulating concentrations of the biomarker tend to be significantly lower in vegetarians and pescatarians than in meat-eaters.
Conclusion
Overall, the study suggests that a vegetarian diet offers protective benefits against several types of cancer, but it also comes with increased risks for others. Experts emphasize the importance of ensuring that all diets, including vegetarian ones, are nutritionally well-designed to avoid deficiencies.
Professor Tim Key, a co-author of the study, noted that dietary patterns prioritizing fruits, vegetables, and fiber-containing foods, while avoiding processed meat, are recommended to reduce cancer risk. He also stressed the need for further research to understand the complex interplay between diet and cancer.
