Vegetables, processed meat, or water: does it matter where we get our nitrate and nitrite from?

Investigating source-dependent nitrate and nitrite intake and risk of colorectal cancer, stomach cancer and bladder cancer

  • Topic: Combination of cancers
  • Institution: Danish Cancer Society Research Center
  • Country: Denmark
  • Status: Ongoing
Researcher: Anne Tjønneland
  • Grant awarded: November 2020

We are delighted with this support from the WCRF, which enables us to investigate sources of nitrate and nitrit from both drinking water and dietary intake and link it to the risk of cancers of the colorectum, bladder and gastric cancer. This is an important research question, where more research is urgently needed to understand the association between nitrate consumption and cancer risk.

– Anne Tjønneland


We consume nitrate and nitrite as part of our everyday diet. Nitrate is found in both water and certain vegetables – mainly green leafy vegetables and beetroot – while both nitrate and nitrite are used as preservatives in processed meat, such as bacon. Interestingly, nitrate-rich vegetables have been shown to be beneficial for our health, while conversely, there is evidence linking nitrate in water and nitrite in processed meat to cancer.

The theory explaining these differences is that vegetables contain antioxidant components, such as vitamin C, which may prevent the formation of cancer-causing compounds. To date no studies have compared these three sources of nitrate and nitrite and investigated their association with specific types of cancer linked to nitrate and nitrite intake.

Aims and objectives

We aim to compare the risk of cancer between people who consume high levels of nitrate and nitrite to people who consume low levels of nitrate and nitrite. More specifically, we will try to determine if there is a difference in the risk of cancer depending on the dietary source of the nitrate and nitrite (vegetables, processed meat, or water).

We also aim to determine if nitrate and nitrite are more likely to cause cancer in people who are more prone to the formation of cancer-causing compounds (smokers and people who eat a low amount of fruits and vegetables containing antioxidant components). We will be looking specifically at types of cancer that have been linked to higher nitrate and nitrite intakes (stomach cancer, colorectal cancer, and bladder cancer).

How it will be done

Between 1993 and 1997, 57,053 Danish residents enrolled in the Danish Diet and Health cohort and were followed-up for 23 years. They completed a questionnaire about their usual dietary habits, which included questions regarding their water intake. From this questionnaire and a geodatabase containing nitrate water levels we will determine each participant’s intake of nitrate from vegetables, nitrate and nitrite from processed meat, and nitrate from drinking water.

Through the nationwide Danish Cancer Registry, we will then determine which of these participants developed cancer and, more specifically, which type of cancer they developed. We will then estimate if the risk of developing cancer is associated with nitrate/nitrite intake from each of these three sources.

Furthermore, we will determine if participants with high nitrate intakes who smoke or eat a low amount of fruits and vegetables (containing the protective antioxidant components), are at a higher risk of developing cancer.

Potential impact

These studies will help to answer pertinent questions about the potential cancer-health hazards of nitrate and nitrite intake with high importance to public health. Results will inform future international guidelines on food safety, public health, caregivers, and will inform policies regarding nitrate and nitrite consumption and potential health hazards.