Common food preservatives have been linked to cancer and type 2 diabetes

Common preservatives used to preserve food and extend shelf life may be linked to a higher risk of many cancers and type 2 diabetes, according to two new studies from France.

“These are very important findings for preservatives that are widely used not only in the French and European markets but also in the United States,” said senior author Mathilde Touvier, principal investigator of the NutriNet-Santé study used to conduct the research.

The NutriNet-Santé study, which began in 2009, compared web-based reports on the diet and lifestyle of 170,000 participants with their medical data stored in the French National Health Service system.

“These are the first two studies in the world to investigate the relationship between food consumption and cancer and type 2 diabetes,” said Touvier, director of research at France’s National Institute of Health and Medical Research in Paris, “and that’s why we have to be very cautious about the message.” Obviously, the results need to be confirmed.

Despite those warnings, “concerns raised about preservatives are another reason to emphasize the personal and public health importance of many fresh, whole, minimally processed foods, mostly plants,” Dr. David Katz said in an email.

Katz, who was not involved in the study, is an expert in preventive and lifestyle medicine who founded the nonprofit True Health Initiative, a global coalition of experts dedicated to evidence-based lifestyle medicine.

Cancer and the Guardian

Cancer study, published Wednesday BMJ The journal closely examined the effects of 58 preservatives on nearly 105,000 people who were cancer-free in 2009 and followed for 14 years. Only those who repeatedly completed a 24-hour, brand-specific food questionnaire were included. People who ate the most preservative-less foods were compared with those who ate the least.

The researchers took a deep dive into 17 preservatives consumed by at least 10% of the participants and found that 11 of them were not associated with cancer. However, six that have been linked to cancer are considered GRAS, or “generally recognized as safe” in food by the US Food and Drug Administration. These include sodium nitrate, potassium nitrate, sorbate, 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 22% higher risk of breast cancer and a 13% increase in all cancers. The World Health Organization has long considered processed meat to be carcinogenic, 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 cancer. These water-soluble salts are used in wine, baked goods, cheeses, and sauces to inhibit mold, yeast, and some bacteria.

Potassium metabisulfite, often used in winemaking and brewing, was associated with a 20% increase in breast cancer and an 11% higher risk of all cancers, according to the study.

Acetates, which come from natural fermentation and are used in foods such as meats, sauces, breads and cheeses, were linked to a 25% higher risk of breast cancer and a 15% increase in cancer in general. Acetic acid, the main component of 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 such as rosemary, and synthetic preservatives such as butylated hydroxyanisole—were also studied. While these more “natural” preservatives are often linked to lower cancer risk when eaten as whole foods, they can be harmful when used as additives, Tuvier said.

“The hypothesis here is that when you isolate a substance from the original matrix of a whole fruit or vegetable, the action on our health may be different from the way it is digested by our gut microbiota,” she said.

Studies have found that only two antioxidant defenses are linked to cancer. Sodium erythorbate and other erythorbates, which are made from fermented sugars, were associated with a 21% higher incidence of breast cancer and a 12% increase in cancer overall.

Erythorbates are used in poultry, soft drinks and baked goods to prevent discoloration and spoilage, 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 a lack of control over variables that may also influence the results. However, a major strength of this study was its ability to adjust for preservatives from natural sources and other foods as well as its “detailed assessment of preservatives through repeated 24-hour dietary records,” according to an editorial published with the study.

“We also looked at what colleagues have published on the effects of these preservative chemicals on animal models, cellular models, gut microbiota, oxidative stress and inflammatory processes that may explain what we observe,” Tuvier said.

In addition, both studies controlled for confounding factors such as physical activity, tobacco, alcohol use, drug use and lifestyle factors, Tuvier said.

“The finding that specific classes of preservatives were associated with an increased risk of selected cancers was robust to all of these adjustments, indicating that this is important and that further research is needed,” Katz said.

Type 2 diabetes and preservatives

The type 2 diabetes study, published Wednesday in the journal Nature Communications, examined the role of preservatives and the potential risk of type 2 diabetes in nearly 109,000 NutriNet-Sente participants who did not have the disease at the start of the study.

Twelve of the 17 preservatives the researchers examined were linked to a nearly 50% higher risk of developing type 2 diabetes in people who consumed high levels.

Five of the same preservatives known to cause cancer, potassium sorbate, potassium metabisulfite, sodium nitrite, acetic acid and sodium acetate, also increased the risk of developing type 2 diabetes. In this case, the probability increased by 49%, according to research.

A sixth preservative – calcium propionate – was also added. It is a white powder used to prevent mold and bacterial growth.

In this study in type 2 diabetes, more than two antioxidants increased the risk. Additives that increase risk by 42% include alpha-tocopherol, the most bioavailable form of vitamin E; sodium ascorbate, which is a buffered form of vitamin C and sodium; rosemary extract; sodium erythorbate, made from fermented sugar; phosphoric acid, a preservative in soda, processed meats, cheeses and other foods; and citric acid, a flavor enhancer, preservative and pH 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, more research will be needed to confirm and extend the findings, said Anaïs Hasenböhler, first author of both studies, a doctoral student in the Nutritional Epidemiology Research Team at Université Sorbonne Paris Nord.

However, Hasenböhler added in a statement, “These new data add to others in favor of a reevaluation of the rules governing the general use of foodstuffs by the food industry to improve consumer protection.”

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