Study on the Effect of Nutrient Restriction on Biological Functions

2004's JSNFS Award for Excellence in Research

Abstract

Excess intake of foods, especially those with a high calorie content, results in obesity, a higher risk of allergy syndrome, and exacerbation of common adult-onset diseases (lifestyle-related diseases). Conversely, it is well known that food restriction reduces the incidence of such problems and delays the onset of several kinds of cancer and lifestyle-related diseases. Furthermore, we have found that in mice, food restriction delays the growth of inoculated tumors and suppresses acute inflammatory responses through improvement of immune function, and that elevation of glucocorticoid levels upregulates immunity. It is also thought that food restriction eliminates lymphocytes that are non-functional or have a low level of activation through apoptosis induced by glucocorticoids, selectively sparing lymphocytes that have a high level of function. Interferon γ and interleukin-2 produced by highly activated CD⁴⁺ T cells activate NK cells and macrophages, which have cytotoxic activity against tumor cells. Activated NK cells and macrophages both act directly as antitumor effectors having cytotoxic/cytostatic activity and also indirectly by production of antitumor cytokines such as TNF-α and interferon γ. Accordingly, the reduced growth of inoculated tumors observed in mice under food restriction can be attributed to improvement of antitumor immunity. From these results it is evident that food restriction is fundamental to good health and that this situation contributes to protection against environmental disruption and saving food resources.