Nutrition: toxicology and pharmacology

Safety limits for nutrient intakes: concepts and data requirements

The possible quantitative methods calculating safety limits for nutrient intakes are related conceptually to those used to calculate safe limits for exposure to environmental chemicals and to the therapeutic index used to assess the relative safety of drugs. The impact of using a fixed SF has been compared with the use of variable SFs. Of the methods identified, the SRM gives lower limits than does the MPM. However, neither of these methods calculates safety limits below the RDA, even for nutrients with narrow margins of safety. The acceptability criteria for toxicity data for use in identifying safety limits are an issue of major importance and must be resolved before calculated limits may be used to support policy or regulatory decisions. An advantage of adopting a standard formula involving systematically varying SFs to calculate safety limits is that the margin of safety below the expected range of toxicity for each nutrient would be systematic, without having the safety limit for any nutrient regress below its RDA. Once the data acceptability criteria were met, the safety limit would be identified objectively. The confidence in and reasonableness of safety limits, regardless of the method used to define them, will be enhanced if the objectives, data criteria, and the quantitative method have been agreed upon ahead of time by groups responsible for nutrition and health policy. Even with such agreement, the confidence in using such procedures to support policy decisions will be improved by the extent and quality of the data base on toxicity and adverse reactions associated with consumption of excessive levels of the nutrients under consideration.

Residue trypsin inhibitor: data needs for risk assessment

Trypsin inhibitor (TI) occurs naturally in many foods from plants, notably soybean protein products. Heat treatment inactivates TI and improves nutritional quality, but residual TI activity of 5 to 20% remains after typical commercial treatments. Chronic feeding of TI or products that contain TI can inhibit trypsin and chymotrypsin, stimulate their secretion, cause hypertrophy and hyperplasia of the pancreas, and lead to adenomas and carcinomas of the exocrine pancreas. In the rat, TI promotes pancreatic carcinogenesis initiated by azaserine. Data needed for possible risk assessment on TI would include 2-year bioassays from animals treated with TI and fed diets carefully controlled for type and amount of fat (which also promotes pancreatic carcinogenesis). The effects of TI on protein nutrition would have to be considered when identifying the maximum tolerated dose. Major reductions in human dietary TI exposure may not be feasible because of the multiple sources of TI, the substantial promotion by other factors such as fat, and the adverse effects of excessive heat on food products. For risk assessment of TI in a particular food, other promotors and the feasibility of decreasing TI intake must be considered.

Nutritional toxicology: basic principles and actual problems

Nutritional toxicology is a specialty that combines the backgrounds and research approaches of nutrition and toxicology. Many problems of substantial importance to health and food safety involve interactions of nutrition process and requirement with the effects of toxicological impact. Solution of these problems requires research that meets the procedural and design criteria of experimental nutrition and these of experimental toxicology. The relationships may be described in three basic categories: (1) influence of nutrition on toxicities; (2) influence of toxicants on nutrition; and (3) toxicities of nutrients. Trypsin inhibitor research, an example of diet impacting on toxicological response, illustrates the necessity of controlling nutritional composition aspects that can confound the results. Prolonged acetaminophen administration provides an example of the effects of toxicants on nutritional requirement and function which could be important for persons with marginal sulphur amino acid intake.

Safety of megavitamin therapy

Carbon compounds that are needed in small amounts in the diet because they are not made in the body of vertebrates are defined as vitamins. Excluded from this definition are vitamins D, K, and niacin which can be synthesized by the organism or, as in the case of vitamin K, by the host's intestinal bacteria. Lack of such vitamins can result in characteristic deficiency diseases. The therapeutic use of such compounds (megavitamin intake) is based on the spectacular effect of vitamins on deficiency diseases; however, evidence that the ingestion of large amounts of vitamins beyond the "Recommended Daily Allowances" (RDA) is beneficial is not within the basic concept of nutrition. Vitamins, like many substances, may be toxic when taken in large quantities, especially the fat-soluble vitamins, and the concept of "more is better" is a common misconception. Vitamin supplements can be suggested only in the unusual cases of patients having inadequate intake, disturbed absorption (genetic or otherwise), or increased tissue requirements. A well-balanced diet that includes a wide variety of foods from each of the four food groups is adequate for the supply of vitamins, as well as other nutrients, in healthy people. This paper will review some of the recent findings regarding vitamin toxicity and the mechanisms of toxicity.

[Drugs and nutrition: interactions and incompatibilities]

A absorção de drogas pode, às vezes, ser consideravelmente alterada conforme as condições em que são ingeridas, ou seja, em jejum ou junto com alimentos ou fluidos. Além disso, alguns componentes alimentares não devem ser ingeridos com certas drogas por apresentarem efeitos adversos. O presente trabalho aborda essas interações e incompatibilidades existentes entre as drogas e os alimentos.

Human nutrition: safety and risk

Man has always been existing in an "oecotoxic" environment and he will be existing in the future, though the noxious factors are changing. Today the output of modern chemical industry and its effects on health attract abundant interest. The risks in nutrition derive from imbalanced nutrition, food borne diseases of microbial origin, environmental contaminants, toxicants naturally present in food, food additives, and food allergens, the most important risks seem to connected with false nutrition and with microbial hazards. The toxic burden of modern man by chemicals can not be judged as the overwhelming nutrition health problem. This burden is only one factor, which--on the genetic background--dynamically interacts with innumerable social, cultural and economic factors, with climate, weather, noise, fatigue and relaxation, with health, functional state, special susceptibility, defense or repair capacity, nutritional situation, water intake, biochronological situation, microecology, coergism of xenobiotics and pharmaca, and others. In this biological system the single potential toxicant plays a quite variable role. The regard of a substance as safe poses a difficult task; the weigh between its toxic properties and its advantages, considering its practical use, should aim at the socially acceptable risk.