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Irradiated foods are foods that have been exposed to a radiant energy source to kill harmful bacteria, insects, or parasites, or to delay spoilage, sprouting, or ripening.
The U.S. Food and Drug Administration approved the first use of irradiation in 1963 on wheat and wheat flour. The FDA sets the maximum radiation dose the product can be exposed to, measured in a unit called kiloGray (kGy) (Illustration by GGS Information Services/Thomson Gale).
There are many reasons that foods are irradiated. The most common reason is for increased food safety. The United States Centers for Disease Control (CDC) estimates that there are about 76 million cases of food-borne illness each year in the United States, resulting in about 5,000 deaths annually. Irradiating foods can reduce the risk of many foodborne illnesses by killing the bacteria or pathogens responsible, or harming them to such an extent that they are not able to reproduce or cause disease. The National Aeronautics and Space Administration (NASA) exposes the food that astronauts eat while in space to a level of irradiation far higher than that approved for commercial use in order to reduce the risk that astronauts will develop illness while in space. Patients who have diseases that severely impair the functioning of the immune system are often fed irradiated foods to decrease the risk that they will develop a serious disease.
Irradiation can also be used to destroy insects and other pests that may be present on produce. When produce is shipped from Hawaii to the mainland United States, it must be fumigated to kill any insects or insect eggs that might be present so that they do not spread to the mainland. Irradiating this produce is sometimes used as an alternative to fumigation, and does not leave residue of chemicals on the produce in the way that fumigation can.
Some fruits and vegetables can be kept fresh longer by the use of low to moderate levels of irradiation.
When exposed to low levels of radiation, potatoes, onions, and other vegetables do not sprout as quickly. Strawberries and other berries can benefit from irradiation as well, as irradiation can significantly delay the growth of mold. Strawberries stay fresh from 3–5 days when they are not irradiated or treated in any way, but can stay fresh and unspoiled for up to three weeks after being irradiated.
Irradiated foods are foods that have been exposed to ionizing radiation. Ions are electrically charged particles, and ionizing radiation is radiation that produces these charged particles. Nonionizing radiation is produced by microwaves, television and radio waves, and visible light. Ionizing radiation is higher in power than these types of radiation, although it is in the same spectrum. The kinds of ionizing radiation used for food irradiation include gamma rays, beams of high-energy electrons, and x rays.
When foods are irradiated, they are exposed to the source of the ionizing radiation for a short time. This radiation produces short-lived compounds that damage the deoxyribonucleic acid (DNA) of living organisms, such as bacteria that are in the food. Because DNA makes up the genes that contain the instructions that tell an organism how to grow and reproduce, once the DNA is damaged the organism cannot do this correctly and will die.
Irradiating foods does not make the foods radioactive in any way. Irradiation done using beams of high-energy electrons or X-rays do not even use any radioactive material. Irradiation done using gamma rays involves exposure of the food to a radioactive substance, usually cobalt 60 or cesium 137, for a short period. The radioactivity of this substance is not in any way transferred to the food that is exposed to it.
Irradiation is not a substitute for safe food handling practices. Although irradiation kills or disables many pathogenic organisms, these organisms can be reintroduced to the foods if cross contamination occurs. In addition, not every pathogen is completely destroyed by irradiation, and leaving foods such as raw meat out at room temperature can allow these pathogens to reproduce to significant levels. Irradiation should be viewed as an extra step to help ensure that the food supply is safe, not as a replacement for food safety practices that are already in place.
Irradiated foods are not expected to interact with any other foods, medicines, or products.
There are no complications expected from consuming irradiated foods. Some concerned groups have expressed fears that the long-term effects of eating irradiated food are unknown. However, many different scientific studies have examined the effects on both animals and humans of consuming irradiated foods. There has not been any evidence that irradiated foods are harmful in either the short or the long term. One study even examined many generations of animals fed irradiated foods and found no harmful effects. Irradiating food is accepted as a safe practice and is endorsed by many organizations including the World Health Organization, the Centers for Disease Control, the United States Food and Drug Administration, and the American Medical Association.
Some parents may have concerns that the vitamin and nutrient content of irradiated foods may be reduced compared to the content of the same foods that have not been irradiated. For most vitamins, minerals, and nutrients this is not the case. Studies have shown that the levels of most vitamins in irradiated foods are not significantly different from the levels in foods that have not been irradiated. Some vitamins however, such as thiamine (vitamin B1), have been found to be sensitive to irradiation. The extent to which such vitamins are destroyed however, depends greatly on type of food being irradiated. Thiamine was found to be decreased by 50% in a water solution that was exposed to radiation, but only decreased by 5% in a dried egg exposed to the same level of radiation. Many vitamins, like thiamine, that are sensitive to irradiation are as sensitive, or even more sensitive, to heat, and are broken down at least as much by the process of canning or heat treatments. Therefore, although levels of some vitamins may be decreased in irradiated foods compared to fresh foods, the levels of these vitamins may be higher in irradiated foods than in comparable canned or otherwise sterilized foods.
Shannon, Joyce Brennfleck ed. Diet and Nutrition Source-book. Detroit, MI: Omnigraphics, 2006.
Sommers, Christopher H. and Xuetong Fan. Food Irradiation Research and Technology. Ames, Iowa: Blackwell Pub., 2006.
United States Department of Agriculture. 1400 Independence Avenue SW, Washington, DC 20250. Website: <http://www.usda.gov>.
United States Centers for Disease Control. 1600 Clifton Road, Atlanta, GA 30333. Telephone: (800) 311-3435. Website: <http://www.cdc.gov>.
United States Food and Drug Administration. 5600 Fishers Lane, Rockville, MD 20857-0001. Telephone: (888) 463-6332. Website: <http://www.fda.gov>.
World Health Organization. Telephone: +41-22-791-2222. Website: <http://www.who.int/en/>.
Organic Consumers Association. “Food Irradiation.” 2007. <http://www.organicconsumers.org/irradlink.cfm>.
Tish Davidson, M.A.