Biochemical Aspects of Food Safety

Abstract

Gross pathological lesions are almost invariably preceded by biochemical lesions, and hence derangement or overloading of biochemical processes may have important consequences with respect to food safety. This concept is discussed in relation to congenital metabolic disorders, enzyme inhibitors in food and drugs, and dose-response characteristics.

Congenital enzyme deficiencies may lead to an inability to utilise normal nutrients, with toxic consequences, or may increase the hazard from naturally occurring anutrients or from additives and contaminants. Toxicity therefore depends on the nature of the recipient as well as on the ingested material; there is no single archetypal man, and ‘zero risk’ is an unattainable goal.

Enzyme inhibitors may exert direct toxic actions by blocking essential physiological processes (e.g. cholinesterase inhibitors). Alternatively, by impairing specific pathways of detoxification, they may increase the toxicity of other compounds (e.g. monoamine oxidase inhibitors and pressor amines). Toxic hazard therefore depends upon the circumstances in which exposure occurs and there are numerous interactions possible between dietary components, or between individual dietary compounds and drugs.

Metabolic pathways may have a limited capacity and may be overloaded. Thus, at one level of exposure a compound may be innocuous, even essential, whereas at a higher level, toxicity is observed. This aspect is discussed in relation to interpretation of dose-response characteristics, dose-dependent qualitative differences in toxicity, or differences in target organs and mechanisms of toxicity, all of which are important in assessing the probable toxic hazards at defined levels of exposure.

Finally, the role of the mixed-function enzymes involved in the metabolism of foreign compounds is discussed briefly. These enzymes may be associated with detoxification processes, but in some instances they produce metabolites which are more toxic than the original substrate. It is not invariably true to say that detoxification mechanisms have evolved to deal with natural anutrients and that ‘natural’ compounds are therefore safer than ‘synthetic’.