Health & Welfare: Preservatives

Fresh facts


"Preservatives may be preserving you…I think that's something you missed."
—from "Eat Starch, Mom," lyrics by Grace Slick

Preservatives may be preserving you, says the rock-and-roll singer. Others believe just as vehemently that food preservatives should be avoided like the plague. What are the facts?

Food ages, just as living organisms do, and by similar chemical processes. One of the most important of the food-aging processes is the oxidation of fats and oils.

Fats and oils contained in foods are subject to spontaneous, self-catalyzed oxidation (autoxidation) reactions when exposed to air. Both the creation and the breakdown of the oxidized fats result in the formation of chemically reactive and highly promiscuous entities called free radicals. Free radicals are mutagens (mutation causers), carcinogens (cancer causers), and a major cause of aging, both in food and in living organisms.

In living plants and animals, special enzyme systems and antioxidants (substances that block uncontrolled oxidation reactions) control free-radical reactions. Uncontrolled free radicals can do serious harm (they are implicated as causative factors in aging, cardiovascular disease, and cancer, as well as a host of less deadly but still unpleasant conditions). Free radicals are necessary, however, in some normal metabolic reactions, such as the burning of food for energy. Without the free-radical-control enzymes (such as superoxide dismutase and glutathione peroxidase) and antioxidants (like vitamins C, E, B-1, B-5, B-6, the amino acid cysteine, the minerals zinc and selenium), all air-breathing organisms on this planet would quickly die.

Foods are tissues of dead animals or plants. The fats and oils in these tissues are still susceptible to oxidation. (Polyunsaturated fats are particularly easy to oxidize.) Since the organism is no longer actively synthesizing the control enzymes and antioxidants, the fats and oils in these foods are especially vulnerable to oxidation (becoming rancid). Manufacturers of foods such as potato chips and cooking oils used to add antioxidants such as BHT (butylated hydroxytoluene) to protect the fats from oxidative degradation. But now, in response to misinformed public clamor for removal of preservatives, most such foods contain no antioxidant additives. The sad fact is that such foods are much more dangerous to eat without added antioxidants than with them.

An experiment in which oils were fed to rabbits showed that even oil that is only slightly oxidized, in which a rancid smell cannot yet be detected, contained enough oxidized fats to inhibit the rabbit alveolar macrophages (lung white blood cells, part of the immune system) from ingesting bacteria. If our white blood cells were as sensitive as a rabbit's (fortunately, they are not), it would take only a few teaspoons of these slightly oxidized oils to reduce the activity of these white blood cells by 50 percent! Our alveolar marcrophages are an important defense against lung cancer; healthy, active alveolar macrophages seek out, identify, kill, and eat cancer cells.

Manufacturers of foods have turned to other means of protecting foods containing fats and oils. One successful method is to package the food in an airtight container such as a tin can, bottle, or plastic bag lined with aluminum foil. Of course, once the container is opened and the food exposed to air, it should be eaten immediately—or you can add your own antioxidants.

Leftovers such as meats develop off-flavors that are a reflection of the level of oxidized (rancid) fats they contain. Whenever we want to save these foods for later eating, we coat them with one of several antioxidants. Ascorbyl palmitate, a fat-soluble form of vitamin C, is particularly good for this because it is a powerful antioxidant and excellent synergist with other antioxidants and has little or no flavor of its own. The food is placed in a self-closing plastic bag, ascorbyl palmitate powder is sprinkled generously over the food, the bag is shaken to disperse the powder, the excess air is squeezed out, the bag is zipped closed, and then the food is refrigerated. You can do a simple experiment comparing food stored in this manner to food stored without added antioxidant that will demonstrate how much longer it takes the treated food to develop a rancid odor.

Autoxidation of fats and oils takes place in the bodies of living plants and animals such as ourselves. The brain is particularly susceptible to autoxidation because it contains a higher content of polyunsaturated fats than any other organ in the body. In one experiment with Sprague-Dawley rats, animals fed semisynthetic diets (which did not significantly affect the death rate) made more errors on a maze test when larger amounts of polyunsaturated fats were fed in place of saturated fats. Free-radical damage resulting from the autoxidation of the excess polyunsaturated fats is a likely explanation.

Many people have strong negative feelings about food preservatives, especially synthetic ones. BHT, which has long been accused of causing cancer, is a good example. Yet the fact is that numerous experiments in both animals and cell cultures have demonstrated that BHT inhibits the development of many different types of cancers. It reduced the number of chromosome breaks in cells exposed to benzoalphapyrene, a powerful carcinogen and a product of almost any type of combustion. In another study, nude mice exposed to ultraviolet light but fed antioxidants (including BHT, which was later found to provide most of the protection) developed far fewer skin tumors than control mice.

In the Soviet Union, BHT is sometimes used as part of cancer therapy. Some scientists believe that the drop in stomach cancer in the United States since World War II is largely due to antioxidants such as BHT added to the food supply.

BHT has also increased the lifespans of several species of experimental animals. Cancer-resistant strains of mice lived about 25 percent longer when given BHT, while a cancer-prone strain lived about 50 percent longer than normal. BHT given to pregnant mice, in one study, increased the lifespan of their offspring by about 20 percent, even though the young mice received no BHT after weaning. This is thought to be due to BHT's ability to prevent mutations.

So the next time you see a package of food in your supermarket bragging that it contains no preservatives, remember that preservatives may be preserving you and that unpreserved fats and oils spontaneously turn into immune-system suppressive carcinogens when exposed to air. We hope that widespread public knowledge of these facts will lead to the return of routine antioxidant preservative use and to the development of even more effective new antioxidants.

A list of scientific literature on this topic is available through REASON. Send a stamped, self-addressed envelope and ask for H&W references, June.

Durk Pearson and Sandy Shaw are consulting scientists and authors.