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Researchers did a dip dive on 17 preservatives consumed by at least 10% of the participants and found 11 of those had no relationship with cancer. However, the six that were linked to cancer are considered GRAS, or “generally recognized as safe” in food by the US Food and Drug Administration. Those include sodium nitrite, potassium nitrite, and sorbates, potassium metabisulfite, acetates and acetic acid.
Sodium nitrite, a chemical salt commonly used in processed meats such as bacon, ham and deli meats, was associated with a 32% increase in the risk of prostate cancer. It’s cousin, potassium nitrate, was associated with a 32% increase in the risk of breast cancer and a 13% increase in all cancers. The World Health Organization has long considered processed meat as a carcinogen, with a direct link to colon cancer.
Sorbates, especially potassium sorbate, were associated with a 26% higher risk for breast cancer and a 14% increase in all types of breast cancers. These water-soluble salts are used in wine, baked goods, cheeses and sauces to prevent molds, yeast and some bacteria.
Potassium metabisulfite, often used in winemaking and brewing, was associated with a 20% increase in breast cancer and 11% higher risk of all cancers, according to the body.
Acetates, which come from natural fermentation and are used in foods such as meat, sauces, breads and cheese, were linked to a 25% higher risk of breast cancer and 15% increase in cancer in general. Acetic acid, the main ingredient in vinegar, was associated with a 12% increase in the risk of all cancers, the study found.
Other types of preservatives – antioxidants such as vitamin C, vitamin E, plant extracts like rosemary and such synthetic preservatives as butylated hydroxyanisole – were also studied. While these more “natural” preservatives are often linked to lower cancer risk when eaten as whole foods, they may be harmful when used as additives, Touvier said.
“The hypothesis here is when you isolate one substance from its original matrix of a whole fruit or vegetable, the action on our health can be different depending on the way our gut microbiota will digest it,” she said.
Only two antioxidant preservatives were linked to cancer, the study found Sodium erythorbate and other erythobates, which are made from fermented sugars, were associated with a 21% higher incidence of breast cancer and 12% increase in cancer overall.
Erythorbates are used to prevent discolouration and spoilage in poultry, soft drinks and baked goods, to name a few. Sodium erythorbate is often used in processed meats to speed up the curing process.
Observational studies are subject to error due to the lack of control over variables that might also influence outcomes. However, a major strength of this study was its ability to adjust for preservatives from natural sources and other food additives, as well as its “detailed assessment of preservative intake, through repeated 24-hour dietary records,” according to an editorial published with the study.
“We also looked at what colleagues have published on the impact of these preservative chemicals on animal models, cellular models, gut microbiota, oxidative stress and inflammatory processes, which may explain what we observe,” Touvier said.
In addition, both studies controlled for such cofounding factors as a physical activity, tobacco, alcohol use, medication use and lifestyle factors, Touvier said.
“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,” Katz said.
Type 2 diabetes and preservatives
The type 2 diabetes study, published on Wednesday in the journal Nature Communications, examined the role of preservatives and the potential risk of type 2 diabetes in nearly 109,000 participants from the NutriNet-Sante cohort who did not have the disease at the start of the study.
Twelve of the 17 preservatives researchers examined were linked with nearly a 50% higher risk of developing type 2 diabetes in people who consumed the highest levels.
Five of the same preservatives that caused cancer – potassium sorbate, potassium metabisulfite, sodium nitrite, acetic acid and sodium acetate – also raised the risk of developing type 2 diabetes. In this case the probability rose by 49%, according to the research.
A sixth preservative, calcium propionate, was also connected. It’s a white powder used to stop mold and bacterial growth.
In this study on type 2 diabetes, more than two antioxidant additives increased risk. Addities that increased risk by 42% included alpha-tocopherol, the most bioavailable form of vitamin E, sodium ascorbate, which is a buffered form of vitamin C and sodium, rosemary extracts; sodium erythorbate, made from fermented sugar; phosphoric acid, a preservative in sodas, rocessed meats, cheeses and other foods; and citric acid, a flavour enhancer, reservative and adjuster with no significant nutritional value.
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, said Anais Hasenbohler, the first author of both studies, who is a doctoral student at the Nutritional Epidemiology Research Team at the Université Sorbonne Paris Nord
However, Hasenbohler added in a statement, “These new data add to other in favour of a reassessment of the regulations governing the general use of food additives by the food industry in order to improve consumer protection.”
