Fungal Bungle
Author：fredabio Date：2017-10-20
By Roxanne Khamsi
Whole Foods and Lebanon may seem like odd bedfellows, but on the matter of dairy products, they’re of one mind. Both have shown distaste for the antifungal known as natamycin, which is commonly used to preserve cheese. The preservative appears on Whole Food’s “Unacceptable Ingredients for Food” list and has been barred from products sold by the grocery chain since 2003. And earlier this year, Lebanon’s health ministry raised objections when the preservative was found in labneh, a strained type of yogurt. Meanwhile, in July it emerged that Russia’s consumer watchdog Rosselkhoznadzor was investigating reports that cheese imported by McDonald’s contained natamycin and threatening to take measures if cheeses at the restaurant contained it. (McDonald’s says that cheese products found on its menu items in Russia do not contain any antifungals whatsoever.)
Considering these actions, you might think that natamycin is an unnecessary, even potentially harmful, additive. But multiple studies have shown natamycin to be safe for human consumption. Furthermore, many companies have embraced the antifungal, which is produced by bacteria, as a natural alternative to chemical preservatives. What makes an ingredient “natural” is, as ever, up for debate. But with producers poised to use natamycin in a growing number of foods—last month the U.S. Food and Drug Administration gave the thumbs up to adding natamycin to yogurt—it’s worthwhile to understand what the preservative is and how it’s been shown to affect the human body.
It might seem counterintuitive to find a mold inhibitor such as natamycin in cheese. Some of the most delicious cheeses derive their flavor from mold—blue cheeses, for instance, look and taste the way they do because of the mold Penicillium roqueforti. But not all molds are friendly to cheese—rogue strains can cause cheese to go bad. Shredded cheese, with plenty of surface area for mold to colonize, is particularly prone to spoilage. Natamycin can change that. It extends the shelf life of cheese from less than two weeks to as long as 38 days, according to the Dutch chemical company DSM, which is one of the producers of natamycin. Browse the local grocery store and you’ll find natamycin in favorites like goat cheese, crumbled feta, and shredded mozzarella.
A few aspects of natamycin may sound less than appetizing. The additive is produced by a type of soil bacteria known as Streptomyces natalensis; it was discovered in 1955 by scientists working for a company that later became DSM. (They found the bacterium in South Africa’s Natal province, for which natamycin got its name.) Some might not savor the idea of eating the waste product of dirt bacteria, or the fact that natamycin appears in the British Journal of Venereal Diseases in a 1975 article about a type of infection known as candidosis affecting the genitals and anus.
But this study is no reason for alarm—rather, it shows the good natamycin can do. The researchers who conducted the study demonstrated that natamycin clears up fungal infections rapidly. Today, doctors commonly prescribe natamycin to treat fungal eye infections, in doses of about 40 milligrams a day. This is much, much higher than the amount of natamycin contained in food. According to a World Health Organization report, if one were to do a calculation based on the assumption that all cheese contained natamycin—which is far from the case—an individual in the U.S. who consumes a lot of cheese would be exposed to about 0.02 milligrams of natamycin per kilogram of body weight daily from these dairy products. That worst-case-scenario estimate translates to about 1.4 milligrams a day for a person weighing 150 pounds—far below the quantities prescribed as medicine.
Even at the high levels associated with antifungal prescriptions, natamycin is unlikely to cause side effects, let alone do any serious harm. Consider, for example, a 1960 study of 10 people with systemic fungal infections who ingested between 50 milligrams and 1,000 milligrams of natamycin per day for up to 180 days. Only those individuals receiving 600 milligrams to 1,000 milligrams per day—hundreds of times more than people consume in food—experienced side effects such as nausea, vomiting, and diarrhea.
After reviewing the scientific evidence, many governmental and health organizations have deemed natamycin safe for consumption. The FDA reviewed and approved natamycin for use in cheese in 1982, and the additive has also received a green light from the European Union, the World Health Organization, and individual countries such as in Australia and New Zealand. Outside the U.S. it has also received approval for use in products beyond cheese, such as meat and wine. In 2009, the European Food Safety Authority issued a report that when natamycin is used for the surface treatment of food products it poses no health risk, in part because it is so poorly absorbed by the body. Even the Center for Science in the Public Interest—which cautions consumers against ingredients like artificial colors and sweeteners—determines it as safe in its “Chemical Cuisine” list of additives. The food watchdog has reviewed the scientific literature and found no reason for concern. “It didn’t cause cancer. It didn’t cause chronic conditions,” says Lisa Lefferts, a senior scientist at CSPI.
Additionally, natamycin has one big benefit over other antimicrobials used in food: The preservative acts against fungi but not bacteria, so it’s not thought to contribute to the troubling tide of antimicrobial resistance tied to overuse of antibiotics in food production. “There’s been no known resistance developed to natamycin because of the way it works,” says Greg Kesel, regional president for DSM Food Specialties in the U.S. And some companies have embraced natamycin as a natural ingredient. In February the Associated Press revealed that Kraft was transitioning away from the preservative sorbic acid and replacing it with natamycin in its Kraft Singles products.
Like a hunk of savory Swiss, the evidence against natamycin contains holes. A study in mice published a few years ago purported to find a link between natamycin and sperm abnormalities in the rodents, but the paper was later retracted at the request of the publisher because of “some fundamental scientific errors” (as well as the authors’ use of a brand name in place of the generic “natamycin”). In the absence of a clear scientific rationale for its ban, Whole Foods has fallen back on an ideology that defines “natural” differently from Kraft. “We really don’t feel that it’s necessary for our cheese products,” explains Cathy Strange, the grocery chain’s global cheese buyer. “We just feel that we want cheese in its natural state.” If that means that your cheese will spoil more quickly in the fridge, so be it. Strange says that the company follows a philosophy that people should consume the cheese that they buy within a few days of purchase.
As one might expect from a supplier, DSM has great confidence in the safety of natamycin, and this spring submitted documentation to the FDA to support the use of the antifungal in yogurt. It makes sense that the company would pursue this avenue: Since the turn of the millennium, per capita consumption of yogurt in the U.S. has doubled. As mold grows on yogurt, it can send threads throughout the product and contribute to the production of toxins. DSM’s wishes were granted on Nov. 21, when the FDA officially sanctioned natamycin for use in yogurt. Of course, there’s one good reason for manufacturers not to put natamycin in their yogurt: They wouldn’t be able to sell it at Whole Foods.
Roxanne Khamsi is a science reporter and editor based in New York City.
2014-12-12
