For several years cytokine production has been associated with infections but it was not suspected that some types of food could also induce cytokines, even in a state of non-infection. Lactic bacteria can induce interferon (IFN) production in human healthy subjects, thus, a better protection against infections would be expected. Therefore, we planned to evaluate the effect of two diets including yoghurt or milk on IFN-gamma production during nutritional recovery in two different situations of malnutrition: (1) children with diarrhoea; and (2) patients with anorexia nervosa (AN). Both the diet including yoghurt of that including milk seemed to increase IFN-gamma production at the end of nutritional recovery in the malnourished children with diarrhoea. The significance of interferon production and the lymphocyte subset increase should be explored to know if a better resistance against pathogens is related to them. Regulation of intestinal absorption and moderate stimulation of interferon production make the yoghurt-based diet a good choice in the nutritional care of children. In the same way, an increase in the IFN-gamma production was observed in AN patients consuming yoghurt. This increase of IFN-gamma production could be considered a biological marker to detect the effect of probiotics on the immune response, especially in the improvement of a deficient nutritional status.