Micronutrient deficiencies are a major problem throughout the world and hundreds of millions of the world's population are affected by micronutrient deficiency disorders. In Europe the prevalence of clinical micronutrient deficiency disorders is less than that in the Third World. However, marginal deficiency of some of the micronutrients might be involved in the aetiology of many of the so-called lifestyle diseases, e.g. cancer, cardiovascular diseases, diabetes, osteoporosis. Supplementing domestic animals with micronutrients in excess of their needs could be one strategy to increase the intake and, thereby, status of micronutrients in the human population. This approach should, however, be considered carefully, in relation to both animal and human welfare. Many micronutrients that may accumulate in animal foods are toxic in high doses. It would also be unethical to expose animals to doses that might have deleterious effects on their health, and concentrations in animal products that might have adverse effects when consumed by man should be avoided. Furthermore, food quality should not be impaired by the supplement. On the other hand, to be relevant in relation to human nutrition, the given micronutrient should accumulate in animal tissue in concentrations that make an important contribution to total intake. Finally, the micronutrient should be incorporated in a way and in a form that is bioavailable to man, i.e. is well absorbed and utilized.