Physicians Committee for Responsible Medicine (PCRM) Position Paper
By Jennifer L. Keller, R.D.
Foodborne illness outbreaks are on the rise in the United States, particularly those related to salmonella species, Escherichia coli O157:H7, campylobacter, Staphylcoccus aureus, and Listeria monocytogenes. According to the Centers for Disease Control and Prevention (CDC), foods of animal origin are the most likely to be contaminated with pathogenic bacteria. Fruits and vegetables that come in contact with manure and water downstream from animal farms may also contain pathogens. In an effort to kill these pathogens and prevent foodborne illnesses while at the same time increasing shelf life of fresh perishables, some foods are now being treated with ionizing radiation.
Despite the U.S. Food and Drug Administration's approval of food irradiation in the United States, there is not clear evidence to prove the safety of the consumption of irradiated foods for humans. The strong ionizing radiation (millions of times the dose of radiation used in a chest X-ray) used to irradiate foods changes the chemical composition of its target foods, and radiolytic products are formed in the process. Some of these created compounds are carcinogenic, and others are likely to cause genetic damage. One study reported that 15 children suffering from protein-calorie malnutrition developed polyploid cells (cells containing multiple copies of their chromosomes) and other abnormal cells after being fed irradiated wheat.1 Another study showed that the effect of irradiated sucrose on human blood cells included inhibited cell mitosis and severely damaged chromosomes, whereas mitotic rate and chromosomes were not affected in human lymphocytes that were treated with unirradiated sucrose.2
As with any thermal treatment, loss of nutrients in foods from animal and plant sources occurs with irradiation, and nutrient loss increases with radiation dose. According to the World Health Organization, thiamin (vitamin B1), vitamin C, and the tocopherols (vitamin E) are extremely radiation sensitive.3 Much of the change in nutrient composition as a result of irradiation is unexplainable-loss of certain nutrients is different for different foods. The most radiation-sensitive, fat-soluble vitamin is vitamin E, and then Carotene, vitamin A, vitamin D, and vitamin K follow in decreasing order of sensitivity. Vitamin B1 is the most radiation-sensitive, water-soluble vitamin, and then vitamin C, vitamin B6, vitamin B2, folate and niacin, and vitamin B12 follow in decreasing order of sensitivity.3
Amino acid composition has also been shown to change as a result of gamma irradiation. For example, irradiation of ground grains at doses above 5 kGy resulted in significant lysine losses in corn, wheat, and soybeans, methionine losses in wheat and corn, and decreased histidine levels in wheat.4
In addition to nutrient losses, irradiated foods may also change in taste, color, and texture after irradiation. For example, vitamin C-rich foods such as fresh fruits, juices, vegetables, and potatoes are unsuitable for high-dose irradiation because vitamin C is a radiation-sensitive nutrient. Irradiation also causes an undesirable change to the sensory qualities of foods, such as color.3 For example, broccoli loses its bright green color when irradiated to kill Listeria monocytogenes.5
Irradiated Animal Products
Irradiated or not, PCRM advises against the consumption of animal products because they are too high in fat in cholesterol and devoid of healthy fiber. Since animal products and animal waste are also the main sources of foodborne pathogens in the food supply, rather than encouraging irradiation of these products, PCRM promotes the consumption of foods from plant sources and supports stronger food safety and security measures to remove pathogenic microorganisms from the food supply. These changes will eliminate contamination of healthy plant foods with foodborne pathogens.
It is the position of the Physicians Committee for Responsible Medicine that there is not sufficient human evidence to support the safety of food irradiation. Treating foods with ionizing radiation reduces their essential micronutrient and amino acid composition, as well as their taste, color, and texture. In order to avoid the health and safety risks of meat, poultry, fish, and other foods from animal sources, PCRM recommends that diets be built from plant foods. In addition, PCRM is pushing for stronger food safety measures to prevent the spread of pathogenic microorganisms and further research into the safety of irradiated foods for humans.
1. Bhaskaram C, Sadasivan G. Effects of feeding irradiated wheat to malnourished children. Am J Clin Nutr. 1975;28:130-135.
2. Shaw MW, Hayes E. Effects of irradiated sucrose on the chromosomes of human lymphocytes in vitro. Nature. 1966;211:1254-1256.
3. High-dose irradiation: wholesomeness of food irradiated with doses above 10 kGy. Report of a Joint FAP/IAEA/WHO Study Group. World Health Organ Tech Rep Ser. 1999;890:1-197.
4. Hooshmand H, Klopfenstein CF. Effects of gamma irradiation on mycotoxin disappearance and amino acid contents of corn, wheat, and soybeans with different moisture contents. Plant Foods Hum Nutr. 1995;47:227-238.
5. Niemira BA, Fan X, Sommers CH. Irradiation temperature influences product quality factors of frozen vegetables and radiation sensitivity of inoculated Listeria monocytogenes. J Food Prot. 2002;65:1406-1410.