We have already covered the link between processed meats and a higher risk of cancer. New research now suggests one key driver may be specific preservatives – and they turn up in far more foods than bacon or ham.
The study, published in The BMJ, adds another piece to the puzzle on how processed foods may influence cancer risk.
Researchers analysed diet and health data from more than 105,000 people between 2009 and 2023. On the food side, they focused on the impact of 17 different preservatives and tracked how these related to cancer and other health outcomes.
They did not find a link between every preservative and cancer risk. However, several additives were clearly associated with higher rates of specific cancers:
- Potassium sorbate – linked with breast cancer and overall cancer risk
- Potassium metabisulphite – linked with overall cancer and breast cancer
- Sodium nitrite – linked with prostate cancer
- Potassium nitrate – linked with overall cancer and breast cancer
- Acetic acid – linked with overall cancer
- Sodium erythorbate – linked with overall cancer and breast cancer
Importantly, most of the preservatives studied—11 out of 17—were not associated with a higher cancer risk. Still, the findings raise reasonable questions about how often these particular additives appear in everyday foods.
What foods do these preservatives show up in?
Processed meats are an obvious source, but they are not the only ones. The study found these preservatives in a range of pantry staples, including:
- Wine
- Beer
- Dried fruit
- Refined grains and breakfast cereals
- Cheese
- Condiments such as tomato sauce and salad dressing
The takeaway is not to panic about every label, but to be more aware of how often these ingredients appear in your regular shop and to lean more heavily on minimally processed foods where you can.
Why might these preservatives be linked to cancer?
While the researchers found an association between certain preservatives and cancer, they did not explore why this link exists. It is “likely to be a combination of factors,” including the overall make-up of the foods these preservatives are used in, says surgical oncologist Dr Anton Bilchik.
Dr Bilchik notes that the exact way these preservatives affect the body and influence cancer risk is still unclear. “Some studies show that preservatives like nitrates and nitrites change the immune environment and can change the gut microbiome, resulting in genetic alterations of cells,” he says. “But there’s a lot more work to better understand the exact relationship of these preservatives and the development of cancer.”
Oncology dietitian Dena Champion agrees and says it is important not to panic. “We cannot say that the preservatives caused the cancer—there may be many other factors that led to that diagnosis,” she says. In addition to altering gut bacteria, some preservatives may promote inflammation in the body, she adds. Inflammation is linked to a range of serious diseases, including cancer.
As for why some preservatives were associated with cancer and others were not, Champion says it may come down to their chemical structure and how the body metabolises them. “Some are broken down and eliminated easily, while others may undergo chemical changes in the body that could be more problematic,” she explains. “The bottom line is that some preservatives appear more concerning than others based on this research, which is actually helpful information.”
It is also worth remembering that the study did not prove that foods containing these preservatives caused cancer. “We have to remember correlation does not always equal causation,” says dietitian Lisa Moskovitz. “Preservatives are most abundant in foods that have excess added sugar, saturated fat and other ingredients that can drive up cancer risk.” Moskovitz also points out that people who eat a lot of preservative-heavy foods may be missing out on protective foods such as fresh fruit, vegetables and other antioxidant-rich plant foods.
Regardless of the mechanism, the study authors say the findings warrant closer investigation. “These findings may have important public health implications given the ubiquitous use of these additives in a wide range of foods and beverages,” they wrote. The results also offer “new insights for the future re-evaluation of the safety of these food additives by health agencies, considering the balance between benefit and risk for food preservation and cancer.”
The bottom line
It is hard to avoid preservatives completely, but it is possible to make a conscious effort to minimise how much ends up on the plate, says dietitian Jessica Cording. “In general, a lot of the foods that [preservatives] are added to are not very nutrient-dense,” she says. “Regardless of the specific preservative, you’re not getting much in the way of protective benefits from those foods.”
Dr Bilchik, agrees. “We really need to think carefully about what we order, what we eat,” he says. One simple strategy is to shop the outer sections of the supermarket first, where fresh produce, dairy and meats are usually found, before heading for the centre aisles. “These are foods that are not necessarily processed to last for long periods of time,” Dr Bilchik says.
“This is just another reason to encourage people to eat more minimally processed foods that have a lot of nutrients that have been shown to help protect against cancer,” Cording says. “Does that mean you can’t enjoy the occasional deli sandwich or ketchup on your burger with a glass of wine? Absolutely not,” adds Moskovitz. “Not only is that unrealistic, but unnecessary if you have an otherwise healthy lifestyle and balanced diet.”
Dr Bilchik also stresses that preservatives are only one piece of a much bigger picture when it comes to cancer risk. “Genetic factors are certainly one part, and we cannot control those,” he says. “In terms of lifestyle, exercise, avoiding smoking and stress reduction… there are so many other factors involved in cancer reduction other than what we eat.”
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