Two recent studies have found that several preservatives commonly found in food items, including soft drinks, candies and jams, may increase the risk of certain cancers and type 2 diabetes.
The cancer-related study, published in The BMJ on Wednesday, examined the effects of 58 preservatives on more than 105,000 participants “without prevalent cancer” over a 14-year period between 2009 and 2023.
According to the researchers, the participants had an average age of 42, with more than 75% being women.
The team calculated participants’ intake of various preservatives using detailed 24-hour dietary records collected throughout the study period. Cancer cases were tracked using health questionnaires as well as official medical and death records.
Participants with the highest consumption of preservative-rich foods were compared with those who consumed the least.
By the end of the follow-up period, more than 4,000 participants had been diagnosed with cancer, with breast, prostate and colorectal cancers being the most common.
For the analysis, researchers focused on 17 preservatives consumed by at least 10% of participants. These included citric acid, lecithins, total sulphites, ascorbic acid, sodium nitrite, potassium sorbate, sodium erythorbate, sodium ascorbate, potassium metabisulfite and potassium nitrate.
The findings showed that 11 of the preservatives had no association with cancer. However, six were linked to an increased risk of several cancer types.
These included potassium sorbate, potassium metabisulfite, sodium nitrite, potassium nitrate, acetic acid and sodium erythorbate. Most of these are non-antioxidant preservatives used to extend shelf life by preventing microbial growth or chemical changes in food.
The study found that sodium nitrite, a chemical salt commonly used in processed meats such as bacon, ham and deli meats, was associated with a 32% increase in prostate cancer risk.
Potassium nitrate was linked to a 22% higher risk of breast cancer and a 13% increase in overall cancer risk. The World Health Organization has long classified processed meat as carcinogenic, with a well-established link to colorectal cancer.
Sorbates, particularly potassium sorbate, were associated with a 26% higher risk of breast cancer and a 14% increase in the risk of all cancers. These water-soluble salts are commonly used in wine, baked goods, cheeses and sauces to prevent moulds, yeast and bacteria.
Potassium metabisulfite, frequently used in winemaking and brewing, was associated with a 20% higher risk of breast cancer and an 11% increase in overall cancer risk.
Acetates, which originate from natural fermentation and are used in foods such as meat, sauces, bread and cheese, were linked to a 25% higher risk of breast cancer and a 15% increase in cancer risk overall.
Acetic acid, the main component of vinegar, was associated with a 12% increase in the risk of all cancers.
The researchers noted that only two antioxidant preservatives were linked to cancer: sodium erythorbate and other erythorbates. These substances, made from fermented sugars, were associated with a 21% higher incidence of breast cancer and a 12% increase in overall cancer risk.
Erythorbates are commonly used to prevent discolouration and spoilage in poultry, soft drinks and baked goods. Sodium erythorbate is also frequently added to processed meats to speed up the curing process.
Meanwhile, other preservatives often considered “more natural”, such as vitamin C, vitamin E and plant extracts like rosemary, as well as some synthetic antioxidants including butylated hydroxyanisole, were associated with a lower cancer risk when consumed as part of whole foods.
However, researchers warned they may have different effects when used as food additives.
“The hypothesis here is that when you isolate one substance from its original matrix of a whole fruit or vegetable, its impact on health can change depending on how the gut microbiota processes it,” said senior author Mathilde Touvier.
The researchers also cautioned that the study was observational and could not establish a direct cause-and-effect relationship between preservatives and cancer.
While the associations remained strong after multiple adjustments, they stressed the need for further research.
“The finding that specific classes of preservatives are associated with increased risk of select cancers was robust to all of these adjustments, indicating it is a matter that warrants respect and requires further research,” David Katz, a specialist in preventive and lifestyle medicine.
TYPE 2 DIABETES AND PRESERVATIVES
The type 2 diabetes-related study, published in the journal Nature Communications on Wednesday, analysed the link between dietary preservatives and the risk of developing type 2 diabetes among more than 108,000 participants who did not have the disease at the start of the study.
Similar to the cancer-related study, participants had an average age of 42, with women accounting for 79.2 percent of the group.
Researchers found that 12 of the 17 preservatives studied were linked to a much higher risk of type 2 diabetes among people who consumed them the most, with the risk increasing by nearly 50%.
Five preservatives already linked to cancer — potassium sorbate, potassium metabisulfite, sodium nitrite, acetic acid and sodium acetate — were also associated with a 49% higher risk of developing type 2 diabetes.
Another preservative, calcium propionate, was also connected to increased diabetes risk.
It is commonly used as a white powder to prevent mould and bacterial growth in foods.
The study also found that several antioxidant additives were linked to a higher diabetes risk.
These included alpha-tocopherol, a form of vitamin E; sodium ascorbate, a form of vitamin C; rosemary extract; sodium erythorbate, made from fermented sugar; phosphoric acid, which is widely used in soft drinks and processed foods; and citric acid, which is used to preserve foods and enhance flavour.
However, Anaïs Hasenböhler, an author of both studies, said more research is needed to confirm and expand the findings since this is the first time preservatives have been linked to cancer and type 2 diabetes.
“Since these two studies are the first to examine the role of preservatives in the development of cancer and type 2 diabetes, much more research will be required to confirm and expand the findings,” he said.
