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Toxicants occurring naturally in foods
BOOK REVIEWS
355
The book, although heavy reading for those outside the Se field, is a comprehensive record of recent developments in this field. Although certain papers tend to be repetitive of each other, this is an unavoidable state of affairs where several different authors are involved. The volume would benefit from more photographic plates, particularly in relation to the toxicity of Se in farm animals. One is, perhaps, a little disappointed that the role of Se is not better documented despite the considerable research effort devoted to it, but one hopes that the Symposium has stimulated much further research. In his final summary, J. G. Bieri remarks that in any new area of science the obvious and relatively simple questions are soon answered but the more difficult and decisive research may take considerably longer to evolve. Se would appear to be at this stage of development.
Toxicants Occurring Naturally in Foods. Food Protection Committee, Food and Nutrition Board. Publication 1354. National Academy of Sciences--National Research Council, Washington, D.C. 1966. p. 301. $6.00. The purpose of this book is to present information relat;ng to the presence of naturallyoccurring toxic substances in the diet of man. At the present ttme, it is impossible to prevent the consumption of toxic materials from this source, but at least the levels of ingestion can be reduced. The widespread occurrence of these toxicants is well illustrated by the 27 chapters in this volume, written by experts commissioned by the Food Protection Committee of the National Academy of Sciences. It is clear that the detoxication mechanisms o f the normal, healthy body are able to cope with the intake of these substances from a reasonably balanced diet prepared in time-honoured ways. But the question which remains unanswered is: What happens in the undernourished, or in persons using an unbalanced diet ? As the various chapters in this book show, foods may contain naturally such substances as goitrogens, oestrogens, carcinogens, lathyrogens, haemagglutinins, stimulants, depressants, allergens, pressor amines, antivitamins, enzyme and cholinesterase inhibitors and many other potentially toxic agents. Many diseases in man, including some forms of cancer and mental disease, could be due to natural foods, but the difficulties of attributing a given disease to any particular foodstuff are great, because people consume a wide variety of foods. The identification of toxic principles in food represents an area of preventive medicine which requires further study. This book is factual but stimulating. Although it is considered that under normal circumstances there is no danger in the ingestion of toxic materials occurring naturally in foods, problems can arise from the simultaneous presence of two or more groups of substances in the material we ingest--those found naturally and those used as direct or indirect additives or as medicines. One or two problems of this kind have already arisen; for example, the hypertensive crises in patients receiving certain antidepressive drugs and eating foods (such as cheese, wine or marmite) containing pressor amines. The chances are that other interactions or the indirect potentiation of the pharmacological actions of drugs will be reported in the future. Valuable accounts of toxic materials that occur in the foods of many different countries are contained in this book and the purpose for which it was written has been achieved. A reviewer can of course find mistakes or omissions in every book he reads, and surely in this field of food toxicology a most important omission is that relating to the carcinogen, dimethylnitrosamine, which is formed from the interaction of nitrate and secondary amine in food and described on pp. 31 and 32, but which does not appear in the Index. This volume,
356
BOOK REVIEWS
however, deserves not only to be read by all interested in food toxicology but also to be retained on their shelves as a first-class reference book.
Potential Carcinogenic Hazards from Drugs. Evaluation of Risks. Edited by R. Truhaut. U I C C Monograph Series. Vol. 7. Springer-Verlag, Berlin, 1967. pp. viii+249. DM 68. In 1965, the international cancer experts met in Paris for a symposium organized by the U I C C (International Union Against Cancer) on the subject of "Potential Carcinogenic Hazards from Drugs". Some repetition of old themes was to be expected in view of the complexity of the cancer problem, but some fresh ideas worthy of serious consideration did emerge to justify the holding of this meeting. An interesting, if not wholly original, analysis of the problem of methodology relating to the potential carcinogenicity of drugs was the subject of a talk by Dr. G. Della Porta, but an earlier contribution on the same topic by Professor I. Berenblum was unremarkable. Dr. Della Porta suggested, on the basis of the available evidence, that adequate testing procedures in rats and mice will uncover the large majority of potential carcinogens, making tests in other species less imperative unless they are called for by special circumstances. Professor R. Doll discussed the relative merits of prospective and retrospective studies in statistical analyses of human tumour incidence aimed at ascertaining carcinogenic potential. Despite the valuable information yielded by retrospective studies, they leave room for considerable doubt because vital information is often missing. Recent trends are laying more and more emphasis on prospective studies, in which groups can be carefully selected and adequately compared with suitable controls. It is surprising that arsenic was mentioned by Professor Doll as an example of a human carcinogen discovered by statistical methods, since despite a close statistical correlation between exposure to arsenic and skin cancer, doubt remains as to how much of the malignancy is due to arsenic and how much to other impurities with which it is almost invariably associated. Some of the evidence for the carcinogenic action of arsenic was reviewed more fully in a communication by Dr. W. G. Hueper later in the symposium. Two important topics relevant to BIBRA's work on the significance of subcutaneous sarcoma received a good deal of attention. Professor H. Druckrey produced evidence to show that true carcinogens have a clear dose-response relationship. The number of tumours is increased by increasing the dose of carcinogen administered, and the latent period is considerably shortened. The latent period and administered dose are inversely related, so that with a sufficiently small dose the time required for tumour induction will be longer than the life-span of the animal. Professor A. C. Frazer discussed fully the implications of this work and suggested that if a dose of a carcinogen is ineffective in the recipient's life-span, there is every reason for considering that a "no-effect" level for the carcinogen exists in the same way as for compounds exerting other forms of toxic effect. This novel suggestion is worthy of serious consideration. One admires the courage of the speaker in going against current trends, which regard carcinogens as taboo, irrespective of potency. As he pointed out, panic measures (legislative or otherwise) are no substitute for a careful evaluation of both the risk involved and the benefits likely to accrue from the use of the drug. The second important topic concerned the carcinogenicity of iron-macromolecular complexes. Briefly reviewing the background to the problem, Dr. F. J. C. Roe clearly indicated that suspicion of carcinogenicity rested in the case of these complexes solely on the induction of local sarcomas by iron-dextran, since other complexes were much less effective in producing tumours. It is refreshing to learn that iron, of which we carry about 9 g, is at last
355
The book, although heavy reading for those outside the Se field, is a comprehensive record of recent developments in this field. Although certain papers tend to be repetitive of each other, this is an unavoidable state of affairs where several different authors are involved. The volume would benefit from more photographic plates, particularly in relation to the toxicity of Se in farm animals. One is, perhaps, a little disappointed that the role of Se is not better documented despite the considerable research effort devoted to it, but one hopes that the Symposium has stimulated much further research. In his final summary, J. G. Bieri remarks that in any new area of science the obvious and relatively simple questions are soon answered but the more difficult and decisive research may take considerably longer to evolve. Se would appear to be at this stage of development.
Toxicants Occurring Naturally in Foods. Food Protection Committee, Food and Nutrition Board. Publication 1354. National Academy of Sciences--National Research Council, Washington, D.C. 1966. p. 301. $6.00. The purpose of this book is to present information relat;ng to the presence of naturallyoccurring toxic substances in the diet of man. At the present ttme, it is impossible to prevent the consumption of toxic materials from this source, but at least the levels of ingestion can be reduced. The widespread occurrence of these toxicants is well illustrated by the 27 chapters in this volume, written by experts commissioned by the Food Protection Committee of the National Academy of Sciences. It is clear that the detoxication mechanisms o f the normal, healthy body are able to cope with the intake of these substances from a reasonably balanced diet prepared in time-honoured ways. But the question which remains unanswered is: What happens in the undernourished, or in persons using an unbalanced diet ? As the various chapters in this book show, foods may contain naturally such substances as goitrogens, oestrogens, carcinogens, lathyrogens, haemagglutinins, stimulants, depressants, allergens, pressor amines, antivitamins, enzyme and cholinesterase inhibitors and many other potentially toxic agents. Many diseases in man, including some forms of cancer and mental disease, could be due to natural foods, but the difficulties of attributing a given disease to any particular foodstuff are great, because people consume a wide variety of foods. The identification of toxic principles in food represents an area of preventive medicine which requires further study. This book is factual but stimulating. Although it is considered that under normal circumstances there is no danger in the ingestion of toxic materials occurring naturally in foods, problems can arise from the simultaneous presence of two or more groups of substances in the material we ingest--those found naturally and those used as direct or indirect additives or as medicines. One or two problems of this kind have already arisen; for example, the hypertensive crises in patients receiving certain antidepressive drugs and eating foods (such as cheese, wine or marmite) containing pressor amines. The chances are that other interactions or the indirect potentiation of the pharmacological actions of drugs will be reported in the future. Valuable accounts of toxic materials that occur in the foods of many different countries are contained in this book and the purpose for which it was written has been achieved. A reviewer can of course find mistakes or omissions in every book he reads, and surely in this field of food toxicology a most important omission is that relating to the carcinogen, dimethylnitrosamine, which is formed from the interaction of nitrate and secondary amine in food and described on pp. 31 and 32, but which does not appear in the Index. This volume,
356
BOOK REVIEWS
however, deserves not only to be read by all interested in food toxicology but also to be retained on their shelves as a first-class reference book.
Potential Carcinogenic Hazards from Drugs. Evaluation of Risks. Edited by R. Truhaut. U I C C Monograph Series. Vol. 7. Springer-Verlag, Berlin, 1967. pp. viii+249. DM 68. In 1965, the international cancer experts met in Paris for a symposium organized by the U I C C (International Union Against Cancer) on the subject of "Potential Carcinogenic Hazards from Drugs". Some repetition of old themes was to be expected in view of the complexity of the cancer problem, but some fresh ideas worthy of serious consideration did emerge to justify the holding of this meeting. An interesting, if not wholly original, analysis of the problem of methodology relating to the potential carcinogenicity of drugs was the subject of a talk by Dr. G. Della Porta, but an earlier contribution on the same topic by Professor I. Berenblum was unremarkable. Dr. Della Porta suggested, on the basis of the available evidence, that adequate testing procedures in rats and mice will uncover the large majority of potential carcinogens, making tests in other species less imperative unless they are called for by special circumstances. Professor R. Doll discussed the relative merits of prospective and retrospective studies in statistical analyses of human tumour incidence aimed at ascertaining carcinogenic potential. Despite the valuable information yielded by retrospective studies, they leave room for considerable doubt because vital information is often missing. Recent trends are laying more and more emphasis on prospective studies, in which groups can be carefully selected and adequately compared with suitable controls. It is surprising that arsenic was mentioned by Professor Doll as an example of a human carcinogen discovered by statistical methods, since despite a close statistical correlation between exposure to arsenic and skin cancer, doubt remains as to how much of the malignancy is due to arsenic and how much to other impurities with which it is almost invariably associated. Some of the evidence for the carcinogenic action of arsenic was reviewed more fully in a communication by Dr. W. G. Hueper later in the symposium. Two important topics relevant to BIBRA's work on the significance of subcutaneous sarcoma received a good deal of attention. Professor H. Druckrey produced evidence to show that true carcinogens have a clear dose-response relationship. The number of tumours is increased by increasing the dose of carcinogen administered, and the latent period is considerably shortened. The latent period and administered dose are inversely related, so that with a sufficiently small dose the time required for tumour induction will be longer than the life-span of the animal. Professor A. C. Frazer discussed fully the implications of this work and suggested that if a dose of a carcinogen is ineffective in the recipient's life-span, there is every reason for considering that a "no-effect" level for the carcinogen exists in the same way as for compounds exerting other forms of toxic effect. This novel suggestion is worthy of serious consideration. One admires the courage of the speaker in going against current trends, which regard carcinogens as taboo, irrespective of potency. As he pointed out, panic measures (legislative or otherwise) are no substitute for a careful evaluation of both the risk involved and the benefits likely to accrue from the use of the drug. The second important topic concerned the carcinogenicity of iron-macromolecular complexes. Briefly reviewing the background to the problem, Dr. F. J. C. Roe clearly indicated that suspicion of carcinogenicity rested in the case of these complexes solely on the induction of local sarcomas by iron-dextran, since other complexes were much less effective in producing tumours. It is refreshing to learn that iron, of which we carry about 9 g, is at last