Are there valid concerns about food irradiation?

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of Znfectious Diseases / Volume 4, Number

at the 32nd South African Congress for Pathology and Microbiology, Pretoria, May 18-20, 1992. 2. Jentsch U, Spencer DA. Causes of mortality in HIV-seropositive patients seen at the Johannesburg Hospital, South Africa, 1991- 1995. Presented at the 36th South African Congress for Pathology and Microbiology, Pretoria, June 1996. 3. Gebo KA, Moore RD, Kenily JC, Chaisson RE. Risk factors for pneumococcal disease in human immunodeficiency virus-infected patients. J Infect Dis 1996; 173:857-862. 4. Fedson DS, Musher DM. Pneumococcal vaccine. In: Plotkin SA, Mortimer EA Jr, eds. Vaccines. 2nd Ed. Philadelphia, PA: WA Saunders, 1994;517-564. 5. Centers for Disease Control and Prevention. Pneumococcal and influenza vaccination levels among adults aged over 65 years: United States, 1995. MMWR Morb Mortal Wkly Rep 1997; 46:913-919. 6. Fedson DS. Improving the use of pneumococcal vaccine through a strategy of hospital-based immunization: a review of the rationale and implications. J Am Geriatr Sot 1986; 33:142-150. 7. Jordens JZ, Paul J, Bates J, Beaumont C, Kimari J, Gilks G. Characterization of Streptococcus pneumoniae from HIVseropositive patients with acute and recurrent pneumonia. J Infect Dis 1995; 172:983-987. 8. GiIks GF, French N, Nakiyingi J, et al. Lack of efficacy of 23valent pneumococcal polysaccharide vaccine in HIV-infected Ugandan adults. Presented at the Pneumococcal Vaccine for the World Conference. Bethesda, MD, September 1998.

Raymond A. Smego Jr, MD, MPH, FACP,DTM&H University

IRRADIATION

I am writing

in response

resulted in widespread deficiencies of these nutrients (none of which are added back to milk).2 Further, Dr. Louria’s letter seems to imply that all foods would be irradiated if the process were widely accepted, and that consumers would not be informed that their foods are irradiated. First, it is unclear that producers have any intention of irradiating all foods. Second, it is already required that any irradiated foods on sale in retail stores be identified by the green radura symbola flower in a broken circle. So consumers not only will be informed of which foods are irradiated but also will have a choice as to whether to buy them. Dr. Louria expresses concerns about the approximately 16 million older Americans who he says have low blood levels of at least one vitamin. Is he not concerned about the older Americans who are particularly susceptible to the adverse effects of food poisoning, or about people taking immunosuppressant medications who also are more susceptible? Currently, most Americans are in very little danger of nutrient deficiency. Citing small nutrient losses as a consequence of irradiation, or any food processing technique, to inveigh against that process denies a huge body of scientific literature on the wholesomeness and enhanced safety of foods so treated.

of the Witwatersrand/SAIMR

Johannesburg, South Africa Gemma Genovese, BSc University of Westminster London, England Keith I? Klugman, MBBCh, MMed, PhD, DTM&H, FRCPath MRC Pneumococcal Disease Research Unit/SAIMR Johannesburg, South Africa FOOD

4

AND

VITAMIN

to Dr. Donald

References 1. Williams AW, Erdman JW Jr. Food processing: nutrition, safety, and quality balances. In: Shils ME, Olson JA, Shike M, Ross AC, eds. Modern nutrition in health and disease. 9th Ed. Baltimore: Williams & Wilkins, 1999. 2. Swaisgood HE. Characteristics of edible fluids of animal origin: milk. In: Fermema OR, ed. Food chemistry. 2nd Ed. New York: Marcel Dekker, Inc., 1985.

LOSS B. Louria’s

Ruth Kava, PhD, RD Director of Nutrition American Council on Science and Health New York, New York

“Coun-

terpoint on Food Irradiation,” which I think contains some misleading statements about food irradiation in the United States as well

as about

the effects

of irradiation

on the

nutritional value of foods. Dr. Louria expresses great concern about losses of vitamins and, possibly, other nutrients as a result of food irradiation. No reputable nutritionist would deny that Irma-

diation can lower the vitamin content of foods. Thiamin and vitamin C likely are the most vulnerable, but the losses of thiamin as a result of irradiation of beef, for example, are less than that which occurs with canning or other thermal processing. And vitamin C losses when fruits and vegetables are irradiated are “small relative to the natural variance in vitamin C content.“’ Pasteurization of milk results in losses of vitamin B,, (lo%>, thiarnin (lo%), vitamin C (lo-25%), and folic acid (10%); but the national acceptance of milk pasteurization has not

ARE THERE VALID CONCERNS ABOUT FOOD IRRADIATION? Dr. Louria’s “Counterpoint on Food Irradiation,” presents several questions of the proponents and processors of irradiated foods. The following is a response to those

points. Dr. Louria’s

first point

is that he does not believe

that

Dr. Steele used the current analysis of food-related illnesses and cites the data of Mead et al.’ However, upon closer inspection, I note that Dr. Steele mentions “An estimated 76,000,000 cases of foodborne infection.. .approximately 6000 deaths.” Mead estimates 76 million

Correspondence

foodborne illnesses and 5200 deaths and does indicate that unknown agents account for 62 million of the illnesses. Certainly not all of the unknown causes will be vegetative bacterial, protozoa& or other pathogens easily controlled by irradiation, and they may not be on a food product that is suitable for food irradiation, but many of these pathogens will be sensitive to ionizing radiation. Yes, two-thirds of the 2 11 million cases of acute gastroenteritis are not foodborne, but that still leaves 76,OOO,OOO cases that are foodborne. Dr. Louria raises the concern of the potential for chromosomal damage and then cites studies performed in India and China. He indicates that his colleagues examined the data from the Chinese study and found borderline statistical significance (P = 0.07). Let us discuss these two studies and others that may have been missed in his review of the literature. Bhaskaram and Sadasivan reported that children suffering from kwashiorkor developed an incidence rate of polyploidy of 0.8% after 2 weeks and 1.8% after 4 weeks of ingesting irradiated wheat.2 This same research facility also reported increased polyploid cells in mice and rats eating irradiated wheat.3,4 These reports caused considerable concern in the scientific community but, upon examination, were found to contain mutually contradictory data and to be at variance with well-established knowledge of biology. 5.hAn example of this was the report of 0% polyploidy in controls and test group children after removal of the treated diet, even though polyploidy is not unusual in human populations.* George et al found no evidence for increased polyploid cells in the bone marrow of rats fed irradiated (0.75 kGy) wheat, within 24 hours of irradiation, for 1 to 6 weeks.’ Tesh et al reported the results of duplicate studies of rats consuming a diet incorporating irradiated wheat that were conducted independently at different laboratories.8 The diets contained 70% by weight of wheat flour that was irradiated to 0.75 kGy prior to milling. The diets were consumed by the rats within 2,4, or 8 weeks from the date of irradiation. There were five males and five females in each diet group in each study. The number of polyploid contigurations per 500 metaphases was counted for each animal. The authors concluded that there were no treatment-related effects on the number of polyploids per 500 metaphases, food consumption, body-weight change, and incidence of mortality. Chi et al specifically looked for any evidence of polyploid cells in the human volunteers ingesting irradiated diets without finding such evidence; however, the study design may have been inadequate to detect abnormalities below the 1% level, because only 50 metaphase lymphocytes were examined for each subject.’ This is the same study to which Dr. Louria refers; however, it is a longer version of the report and published in English. Renner examined metaphase preparations of chromosomes from bone marrow cells of Chinese hamsters

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for evidence of mutagenic effects following the ingestion of an unirradiated or a radiation-sterilized diet (45 kGy) for 6 weeks and found incidences of 0.06% and 0.32% polyploid cells, respectively.” In the initial investigations, 100 metaphases were counted per animal and 300 in sub sequent studies. The incidence of structural chromosomal aberrations did not increase. Further studies revealed that animals ingesting feed immediately after irradiation to doses of 20 kGy or higher developed increased rates of polyploidy. The incidence did not increase when doses of 100 kGy were used, and never exceeded 0.5%. No such effect was found at doses of 10 kGy or less and when the irradiated feed was stored for 6 weeks before use. The ingestion of small amounts of 0.3% H,O, with the unirradiated diet also produced an increased incidence of polyploidy. Because the incidence of polyploidy returned to the control level within a maximum of 6 weeks and because the effect was not dose related, the author concluded that the result was not a mutagenic effect. The effects of low-dose gamma irradiation on the content of thiamine (B,), riboflavin (B,), niacin, pyridoxine (B& and cobalamin (B,2) in pork chops, and thiamine, riboflavin, and niacin in chicken breasts was studied.” Over the range of dose and temperature studied, it was possible to derive a mathematic expression for predicting the losses. A calculation was made of the effect of the loss of thiamine, riboflavin, and niacin due to irradiation on the overall loss of these vitamins in the American diet. The losses of riboflavin and niacin were of the order of a fraction of a percent. Pork is an important source of thiamine, but the calculated loss with irradiation at 1.0 kGy of this vitamin in cooked pork was only 1.5%, if it is assumed that all pork would be irradiated. Is there the potential for loss of vitamin C in irradiated fruits and vegetables? Yes, but not at the doses that are practical for these products. Some ascorbic acid will be converted to its oxidized dehydro form; however, dehydro ascorbic acid is every bit as usable in humans as its unoxidized form.12 At doses that are significantly higher than those that are applicable for insect disinfestation or for sprout inhibition in potatoes, some loss in total ascorbate may occur. On the whole, Dr. Louria’s concerns do not seem to be well-founded. References 1. Mead PS, Slutsker L, Dietz V, et al. Food-related illness and death in the United States. Emerg Infect Dis 1999; 5:607-625. 2. Bhaskaram C, Sadasivan G. Effects of feeding irradiated wheat to malnourished children. Am J Clin Nutr 1975; 28:130-135.

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3. Vijayalaxmi. Cytogenetic studies in rats fed irradiated wheat [Letter]. Int J Radiat Biol Relat Stud Phys Chem Med 1975; 27:283-285. 4. Vijayalaxmi. Genetic effects of feeding irradiated wheat to mice. Can J Genet Cytol 1976; 18:231-238. 5. KesavanPC,Sukhatame PV Surunraryof the technical report on the data of NIN, Hyderabad and BARC, Bombay, on the biological effects of freshly irradiated wheat. Report submitted to the Joint FAO/IAEA/wH 0 Export Committee on the Wholesomeness of Irradiated Food, 1996. 6. Federal Drug Administration. Irradiation in the production, processing, and handling of food. Proposal. Federal Regulation 51:13376-13399. Washington: FDA, 1986. 7. George KP Chaubey RC,Sundaram K, Gopal-Ay-EngarAR.Frequency of polyploid cellsin the bone marrow of rats fed irradiated wheat. Food Cosmet Toxic01 1976; 14:289-291. 8. Tesh JM, Davidson ES,Walker S, Palmer AK, Cozens DD, Richardson JC. Studies in rats fed a diet incorporating irradiated wheat. Technical Report IFIP-R45.International Project in the Field of Food Irradiation. Karlsruhe, Federal Republic of Germany: Institut fiir Stmhlenteclmologie, 1977. 9. Chi H, Shiping G, Maoqi W, Wenming L, Wenming C,Yin D. A feeding trial of irradiated diet in human volunteers. Presented at United Nations Food and Agriculture Organization/International Atomic Energy Agency (FAO/IAEA). Seminar for Asia and the Pacific on Practical Applications of Food Irradiation, Shanghai, China, April 7- 11, 1986. 10. Renner HW Chromosome studies on bone marrow cells of Chinese hamsters fed a radiosterilized diet. Toxicology 1977; 8:213-222. 11. Fox JB Jr,Thayer DW,Jenkins RK, et al. Effect of gamma irradiation on the B vitamins of pork chops and chicken breasts. Int J Radiat Biol 1989; 55:689-703. 12. Todhunter EN, McMillan T, Ehmke DA. Utilization of dehydroascorbic acid by human subjects. J Nutr 1950; 42297-42308.

Donald W Thayer, PhD Food Safety Research Unit USDA, NAA, Eastern Regional Research Center Wyndmoor, Pennsylvania

FOOD IRRADIATION, NEEDED AMERICAN

VITAMIN STUDIES

LOSS,

AND

The American Council on Science and Health has long been a vigorous proponent of food irradiation. Indeed, when I first got involved in this debate, before I had either stated my views in public or published any article, a representative of the American Council on Science and Health wrote a long letter to the Dean of my medical school demanding to know why I was being allowed to speak on this issue and suggesting that I would disgrace the medical school because of my ignorance on the subject. Dr. Kava agrees that irradiation can lower the vitamin content of food. Actually, the most vulnerable of the vitamins is not thiamin or vitamin C, but rather vitamin E. In one of the five studies cited by the FDA as impec-

cable in supporting the safety of food irradiation, the irradiation virtually eliminated vitamin E and produced vitamin E deficiency in the rats, creating abnormalities that were not reversed until this was discovered and vitamin E was added. One of the potential problems with irradiated food is that with further processing there can be additional and excessive vitamin losses. Furthermore, nutrient loss is likely to be dose-related; additionally, there may be differences in nutrient loss with the newer technique of linear acceleration compared to irradiation with cobalt or cesium. If Dr. Kava agrees that irradiation can reduce vitamin content, why not then agree to what I have asked, namely that every food that is irradiated before it is sold to the public be checked for vitamin or other nutrient loss at the dosage and with the irradiation technique to be used. The results should then be put on the label. I cannot imagine any nutritionist opposing this. In regard to all foods being irradiated, one of the country’s most vocal epidemiologists in a meeting in Washington, DC, urged government and the industry to make sure that irradiated foods could not come into contact with non-irradiated foods. That means virtually irradiating everything. To suggest that the radura is proper labelling is ludicrous. Besides, I am sure the industry intends to remove all evidence of irradiation as soon as possible. If a food is irradiated, that should be stated on the label, not just indicated by a flower-like or smiling face-like symbol. Dr. Kava gets to an important point when asking if I am concerned about older adults who are susceptible to food poisoning or who are on immunosuppressive medications. Of course I am. That should be a central issue in the debate. Only a small percentage of older people are going to experience food poisoning severe enough to require hospitalization, and only a small percentage will be on immunosuppressive medications. On the other hand, irradiating their foods exposes all of them to potential nutritional deprivation. Looked at another way, food irradiation will have benefits in preventing a certain percentage of the cases of foodborne diarrhea, but the tradeoff could be less nutritious foods for a huge number of people in the United States and the rest of the world. That may be an unacceptable trade-off and, at the very least, it is a trade-off that should be discussed. I think it is not productive to continue attacks on the Indian study as Dr. Thayer does in his letter. There is a nice review of the whole issue in Nutrition Research.’ That review analyzes differences in studies and offers some suggestions as to differences in methodologies that may account for the differences in results. The Indian study has major flaws and is controversial, but it has not been refuted. The Chinese study is still unsettled. An article in the Chinese Medical Journal is cited.’ Dr. Thayer refers to a presentation in 1986, that is hardly a peerreviewed publication. I do not think it is worth debating