Elucidation of the function and mechanism of the innate immune system has shown that natural killer (NK) cells play an important role, particularly for protection against viral infection and cancer; they also seem to participate in maintaining the health of senescent people and their longevity. The fundamental aspects of innate immunity and NK cells is explained first in this review. Bibliographic information on effective nutrient composition, food ingredients, and life style for activating NK cells is then presented and explained.
