Unless you grow all your food in your own garden and prepare all your meals from scratch, it's almost impossible to eat food without preservatives added by manufacturers during processing. Without such preservatives, food safety problems would get out of hand, to say nothing of the grocery bills. Bread would get moldy, and salad oil would go rancid before it's used up.
Food law says preservatives must be listed by their common or usual names on ingredient labels of all foods that contain them-- which is most processed food. You'll see calcium propionate on most bread labels, disodium EDTA on canned kidney beans, and BHA on shortening, just to name a few. Even snack foods--dried fruit, potato chips, and trail mix--contain sulfur-based preservatives.
Manufacturers add preservatives mostly to prevent spoilage during the time it takes to transport foods over long distances to stores and then our kitchens. It's not unusual for sourdough bread manufactured in California to be eaten in Maine, or for olive oil manufactured in Spain to be used on a California salad. Rapid transport systems and ideal storage conditions help keep foods fresh and nutritionally stable. But breads, cooking oils, and other foods, including the complex, high-quality convenience products consumers and food services have come to expect, usually need more help.
Preservatives serve as either antimicrobials or antioxidants-- or both. As antimicrobials, they prevent the growth of molds, yeasts and bacteria. As antioxidants, they keep foods from becoming rancid, browning, or developing black spots. Rancid foods may not make you sick, but they smell and taste bad. Antioxidants suppress the reaction that occurs when foods combine with oxygen in the presence of light, heat, and some metals. Antioxidants also minimize the damage to some essential amino acids--the building blocks of proteins--and the loss of some vitamins.
Safety Questions
Consumers often ask the Food and Drug Administration about the safety of preservatives, and if there's a system in place to make sure preservatives are safe.
Many preservatives are regulated under the food additives amendment, added to the Federal Food, Drug, and Cosmetic Act in 1958. The amendment strengthened the law to ensure the safety of all new ingredients that manufacturers add to foods. Under these rules, a food manufacturer must get FDA approval before using a new preservative, or before using a previously approved preservative in a new way or in a different amount. In its petition for approval, the manufacturer must demonstrate to FDA that the preservative is safe for consumers, considering:
Also, a preservative may not be used to deceive a consumer by changing the food to make it appear other than it is. For example, preservatives that contain sulfites are prohibited on meats because they restore the red color, giving meat a false appearance of freshness. (The U.S. Department of Agriculture regulates meats, but depends on the FDA regulation to prohibit sulfites in meats.)
The food additive regulations require the preservative to be of food grade and be prepared and handled as a food ingredient. Also, the quantity added to food must not exceed the amount needed to achieve the manufacturer's intended effect.
Regulations about the use of nitrites demonstrate the scrutiny given to the use of additives. Nitrites, used in combination with salt, serve as antimicrobials in meat to inhibit the growth of bacterial spores that cause botulism, a deadly food-borne illness. Nitrites are also used as preservatives and for flavoring and fixing color in a number of red meat, poultry, and fish products.
Since the original approvals were granted for specific uses of sodium nitrite, safety concerns have arisen. Nitrite salts can react with certain amines (derivatives of ammonia) in food to produce nitrosamines, many of which are known to cause cancer. A food manufacturer wanting to use sodium nitrites must show that nitrosamines will not form in hazardous amounts in the product under the additive's intended conditions of use. For example, regulations specify that sodium nitrite, used as an antimicrobial against the formation of botulinum toxin in smoked fish, must be present in 100 to 200 parts per million. In addition, other antioxidants, such as sodium ascorbate or sodium erythorbate, may be added to inhibit the formation of nitrosamines.
As scientists learn more about the action of certain chemicals in our bodies, FDA uses the new data to reevaluate the permitted uses of preservatives. Two examples are the commonly used preservatives butylated hydroxyanisole (BHA) and sulfites.
BHA
BHA and the related compound butylated hydroxytoluene (BHT) have been used for years, mostly in foods that are high in fats and oils. They slow the development of off-flavors, odors, and color changes caused by oxidation. When the food additives amendment was enacted, BHA and BHT were listed as common preservatives considered generally recognized as safe (GRAS). GRAS regulations limit BHA and BHT to 0.02 percent or 200 parts per million (ppm) of the fat or oil content of the food product.
Lawrence Lin, Ph.D., of FDA's Center for Food Safety and Applied Nutrition, explains, "The 0.02 percent allowed relates only to the product's fat content. For example, if a product weighs 100 grams and one of those grams is fat, the quantity of BHA in the product cannot exceed 0.02 percent of that one gram of fat."
BHA is also used as a preservative for dry foods, such as cereals. But because such foods contain so little fat, the amount of BHA allowed cannot be measured against the percentage of fat, explains Lin. Therefore, as manufacturers petitioned FDA for approvals for this use, the agency set limits for each type of food. On cereals, for example, FDA limited BHA to 50 ppm of the total product.
In 1978, under contract with FDA, the Life Sciences Research Office of the Federation of American Societies for Experimental Biology (FASEB) examined the health aspects of BHA as part of FDA's comprehensive review of GRAS safety assessments. FASEB concluded that although BHA was safe at permitted levels, additional studies were needed.
Since that evaluation, other studies suggested that at very high levels in the diets of laboratory animals, BHA could cause tumors in the forestomach of rats, mice and hamsters, and liver tumors in fish. Many experts examined the data and concluded the tests did not establish that such problems could exist in humans, mostly because humans do not have forestomachs. Other studies showed that BHA was protective, inhibiting the effect of some chemical carcinogens, depending on the conditions of the tests.
Studies on BHA were reviewed by scientists from the United Kingdom, Canada, Japan, and the United States. Their findings were published in 1983 in the Report of the Working Group on the Toxicology and Metabolism of Antioxidants and reviewed in the 1990 Annual Review of Pharmacology and Toxicology. The 1983 report stated that data from a Japanese study showed a high incidence of cancerous tumors and papillomas (benign tumors of the skin or mucous membranes) of the forestomach of treated rats and that the effect was dose-related. The report also mentioned the possible existence of a no-effect level, based on dose response, and noted that the level which produced cancer in this study was many thousands of times higher than the level to which humans are exposed.
In November 1990, Glenn Scott, M.D., a physician then living in New York who has since moved to Cincinnati, filed a petition with FDA, asking the agency to prohibit the use of BHA in food. Scott cited animal studies to support his request. Before acting on Scott's petition, however, FDA asked FASEB to reexamine the scientific data on BHA. By March 1994, FASEB is scheduled to provide FDA with a report on the most current scientific information bearing on the relationship of BHA ingestion to cancer in animals.
Sulfites
Sulfites are used primarily as antioxidants to prevent or reduce discoloration of light-colored fruits and vegetables, such as dried apples and dehydrated potatoes. They are also used in wine-making because they inhibit bacterial growth but do not interfere with the desired development of yeast.
Sulfites are also used in other ways, such as for bleaching food starches and as preventives against rust and scale in boiler water used in making steam that will come in contact with food. Some sulfites are used in the production of cellophane for food packaging.
FDA prohibits the use of sulfites in foods that are important sources of thiamin (vitamin B1), such as enriched flour, because sulfites destroy the nutrient.
Though most people don't have a problem with sulfites, some do. FDA's sulfite specialist, consumer safety officer Joann Ziyad, Ph.D., points to a bookcase full of binders and says, "Those are the case histories of adverse reactions to sulfites that have been reported to FDA. Since 1985, when the agency started reporting on sulfites through the Adverse Reaction Monitoring System, over 1,000 adverse reactions have been recorded."
As reports of adverse reactions mounted, FDA asked FASEB to reexamine the use of sulfites. FASEB's report, released in 1985, concluded that sulfites posed no hazard to most Americans, but that they were a hazard of unpredictable severity to people who were sensitive to the substance. Based on the FASEB study, FDA estimated that more than 1 million asthmatics are sensitive or allergic to the substance.
In 1986, FDA ruled that sulfites used specifically as preservatives must be listed on the label, regardless of the amount in the finished product. Sulfites used in food processing but not serving as preservatives in the final food must be listed on the label if present at levels of 10 parts per million or higher. Regulations issued in 1990 extended these required listings to standardized foods.
Also in 1986, FDA banned the use of sulfites on fruits and vegetables intended to be eaten raw, such as in salad bars and grocery store produce sections. Grocers and restaurateurs were using them to maintain the color and crispness of fresh produce. (Even before the FDA ban, industry trade groups had persuaded many of their members to stop using sulfites on fresh produce.)
FDA plans to repropose a ban for sulfites on fresh, peeled potatoes served or sold unpackaged and unlabeled, such as for french fries in restaurants. An earlier FDA rule dealing with sulfites on potatoes was invalidated by the court in 1990 on procedural grounds.
In addition, sulfite-sensitive consumers are learning how to avoid sulfites. Consumer awareness combined with FDA actions have slowed the number of adverse reaction reports. Ziyad says that from 1990 to 1992, fewer than 40 were reported, and at press time, there had been only three reports in 1993.
Ziyad says the only way FDA can know about sulfite-sensitivity problems is through consumer and physician reports. Adverse reaction reporting is totally voluntary, and FDA encourages physicians to report patients' reactions to sulfites. But there are times when such reactions are not medically treated because the individual doesn't go to the doctor with the condition or the symptoms are not recognized. Such information would help FDA evaluate the current status of problems with foods among sulfite- sensitive individuals.
The agency's Adverse Reaction Monitoring System collects and acts on complaints concerning all food ingredients including preservatives. If you experience an adverse reaction from eating a food that contains sulfites, describe the circumstances and your reaction to the FDA district office in your area (see local phone directory) and send your report in writing to:
Adverse Reaction Monitoring System (HFS-636)
200 C St., S.W.
Washington, DC 20204
Puzzling It Out
Preservatives are a puzzle for many consumers that can sometimes raise safety concerns. Even though these concerns are usually unfounded, some industry publications are reporting attempts to find naturally occurring substitutes for synthetic antioxidants. In a 1990 article, one such publication, Inform, says alternatives to synthetics are commercially available in the United States, although most are generally more costly or have other drawbacks. For example, tocopherol (vitamin E), generally is not as effective in vegetable fats and oils as it is in animal fats. Also, some herbs and herb extracts, such as rosemary and sage, can do the work of antioxidants, but they impart strong color or flavors. And just because these are plant-derived doesn't necessarily mean they are always safe. Inform points to the FDA rule that newly identified natural antioxidants, like other new food additives, must undergo rigorous toxicological tests before they can be approved.
As an additional alternative to synthetic antioxidants, the edible oil industry is increasingly using ultraviolet-barrier packaging and filling under nitrogen to protect the product's stability.
FDA scientists will continue to carefully evaluate all research presented to the agency on new preservatives to ensure that substances added to food to preserve quality and safety are themselves safe.
Judith E. Foulke is a staff writer for FDA Consumer.
People who are sulfite-sensitive should know which foods may possibly contain sulfites. But it's not always obvious by the chemical names on the label which ingredients are sulfites. Currently, there are six sulfiting agents allowed in packaged foods. The names by which they are listed on food labels are:
The symptom most reported by sulfite-sensitive people is difficulty breathing. Other problems range from stomachache and hives to anaphylactic shock. In addition to knowing which food preservatives are sulfites and which foods are likely to contain them, sulfite-sensitive consumers can help themselves avoid health problems by following these suggestions:
For example, lemon juice in your tea or splashed on your salad could be a source of sulfites. Fresh-squeezed lemon is OK, but bottled lemon juice often contains sodium bisulfite.
--J.E.F.
by Maribeth LaVecchia
Maribeth LaVecchia is a Consumer Safety Officer with FDA/CFSAN's Office of Premarket Approval.
* Updated Information: Please call the CFSAN Outreach and Information Center at 1-888-SAFEFOOD.