In the western industrialized world, malnutrition of the lactating mother is not a problem any more. However, new problems, the chemical pollutants in breastmilk, have given rise to concern. Since the seventies, pollution of breastmilk with PCBs and dioxins has taken place. After World War II, more and more PCBs and dioxins entered the environment. Because of the low half-life of these chemicals, persistence leading to accumulation in animal and human fat has taken place. The baby, before birth and when breast-fed, is the highest animal in the food chain, consuming the most concentrated amount of PCBs and dioxins in his/her daily fat intake. Exposure before and after birth has given rise to subtle abnormalities in similar to 10% of the newborns in the Netherlands. These subtle abnormalities are a disturbed cognitive development and a delayed motor-development. Severe vitamin K deficiency can be caused by these contaminants as well. Because of the very threatening situation, a study was performed to look for the possibilities of prevention by influencing the diet of the lactating mother. Two diets were tested for their ability to reduce concentrations of dioxins in human milk. The diets were a low-fat/high-carbohydrate/low-dioxin diet (about 20% of energy intake derived from fat) and a high-fat/low-carbohydrate/low-dioxin diet. Despite significant influences of these diets on the fatty acid profiles, no significant influence on the dioxin concentrations in breast milk could be found. We conclude that short-term dietary measures will not reduce dioxin concentrations in human milk. A lowering of intake of these chemicals must take place years before the mother becomes pregnant. An important food source for the mother is cow's milk and milk products, and these dairy products are responsible for half the daily exposure to PCBs and dioxins. So the level of dioxins and PCBs in dairy foods must be lowered. But also in other important foods like fish, a lowering is necessary.