A recent study has warned that high consumption of nitrites, a compound found in a number of foods and vegetables, may be linked to an increased risk of bowel cancer, especially in men.
Concerns about nitrites have long focused on processed meats, as they are used in some products to help preserve them and maintain their color. But the new study suggests that the source of nitrites may not be the most important factor, and that consuming large amounts from various food sources may be linked to an increased risk of the disease.
In a study published in the Journal of the National Cancer Institute, researchers analyzed the dietary data of 82,009 middle-aged Swedish adults who completed questionnaires about their eating habits in 1997, 2009, and 2019. The study excluded people who had previously been diagnosed with cancer, with the exception of non-melanoma skin cancer.
The researchers relied on data from the Swedish Food Agency, along with special measurements of nitrite levels in hundreds of foods, to estimate the participants' average daily consumption of this substance.
The results showed that meat products were the main source of nitrites for men, accounting for slightly more than half of their intake, while processed meats contributed about a quarter. Approximately 20% of intake came from vegetables, cheese, and other dairy products.
During a 20-year follow-up period, 3,170 participants developed colorectal cancer. Men who consumed the highest amounts of nitrites were 23% more likely to develop the disease than those who consumed the lowest amounts.
The researchers did not find a statistically significant relationship between nitrite consumption and the risk of bowel cancer in women.
After accounting for other factors that can influence risk, such as age, family history, weight, smoking, and fiber consumption, the researchers found that higher nitrite intake was associated with an increased risk of colorectal cancer in men, regardless of the source of the substance.
The link was most pronounced in cancers affecting the lower part of the intestine, where the risk of developing the disease increased by 50% in men who consumed the highest amounts of nitrites compared to those who consumed the least.
Researchers believe the lower part of the intestine may be more susceptible to the harmful compounds formed when nitrite breaks down during digestion. Previous studies have indicated higher levels of DNA damage associated with these compounds in this part of the intestine.
However, the researchers stressed that the study does not prove that nitrite directly causes bowel cancer, emphasizing the need for further research to confirm the relationship and understand the mechanisms that may explain it.
Nitrites are substances used in some processed meats to help extend their shelf life and preserve their color. These substances can react with proteins during digestion to form compounds known as nitrosamines, which can damage body cells and may be linked to an increased risk of cancer.
The UK's National Health Service (NHS) recommends limiting the consumption of processed meats and warns against excessive consumption of red meat due to its link to an increased risk of certain types of cancer.
Conversely, a large study conducted by researchers at Oxford University and published in February showed that vegetarians may face a higher risk of bowel cancer compared to meat-eaters. The researchers stated that these findings do not mean that eating meat protects against the disease, but rather indicate that cancer risk is influenced by multiple dietary and health factors.
