By Kathryn Lougheed
As if we needed a reason to avoid a diet solely consisting of salad, researchers at the University of Aberdeen have shown that certain vegetables can lead to the production of cancer-causing compounds in the gut. However a balanced diet containing plenty of dietary fibre and vitamin C can protect against the formation of these compounds.
This isn't the first time foodstuffs have been potentially linked to cancer. Red meat has previously been implicated as having a role in the development of bowel cancer - worrying in light of the fact that UK men eat an average of 90 grams of red meat a day compared with the recommended 70 grams.
In a presentation at the British Science Festival, Dr Silvia Gratz explained that, like red meat, vegetables including lettuce, radishes and spinach could also do us more harm than good if not eaten as part of a balanced diet.
Dr Gratz and colleagues, from the University of Aberdeen, fed obese men nine different diets containing varying levels of red meat, fibre, vitamin C and nitrate-rich vegetables. They then measured the levels of N-nitroso compounds in stool samples. N-nitroso compounds are carcinogens already known to be produced in the gut of those following a high-meat diet.
While red meat and nitrate-rich vegetables such as lettuce, radishes, spinach, beetroot, turnips and carrot caused an increase in N-nitroso compounds, vitamin C and dietary fibre proved to be protective. Vitamin C probably exerts its effects via its antioxidant properties; the fibre result is harder to explain. Dr Gratz suggested that the explanation might have a microbial component - bacteria living in the gut have a huge impact on digestion and overall health.
Dr Gratz says her study "highlights the importance of balancing potentially-problematic foods such as red meat and high-nitrate foods such as some leafy and root vegetables with protective foods that are rich in vitamin C and dietary fibre."