Interaction between cytokines, nutrition and infection

Present evidence suggests that cytokines, as intercellular mediators, play a key role in the nutrition-infection complex. Protein-calorie malnutrition, deficiency of fatty acids, vitamins, trace elements, impair cytokine production. By the other hand, infections increase pro-inflammatory cytokine production interfering with nutritional status by impairing metabolic activity and by inducing anorexia. Elevated cytokine levels in human milk represent a physiological phenomenon and is not necessarily associated to infectious processes. Research on the kinetical behaviour of pro-inflammatory cytokine in each of the above mentioned conditions should be performed as a goal for future investigations. The development of comprehensive studies on the influence of dietary supplementation on cytokine production could be of clinical interest. However, the results obtained should be considered with caution because cytokines are highly interdependent and changes in some of them could affect target tissue. For instance dietary supplementation with (n-3) polyunsaturated fatty acids (PUFA), generally recommended in elderly subjects for reducing or preventing inflammatory diseases, down-regulate cytokine production, but secondarily suppress cell-mediated immune response, effect that may not be desirable. When evaluating cytokine production during dietary supplementation programs is important to consider food consumption, age, presence of infection and/or stress. Future clinical trials are needed to define the diet composition that will have an anti-inflammatory effect maintaining a normal immune response. Finally, the better understanding of nutrition-cytokine interaction may also be important as this information could be relevant for treatment of patients with cancer or other diseases in which malnutrition is present.