Free radical theory of aging: history.


Harman D.






Aging is the accumulation of changes responsible for the sequential alterations that accompany advancing age and the associated progressive increases in the chance of disease and death. These changes can be attributed to disease, environment, and the inborn aging process. The aging process is now the major risk factor for disease and death after about age 28. The free radical theory of aging arose in 1954 from a consideration of aging phenomenon from the premise that a single common process, modifiable by genetic and environmental factors, was responsible for the aging and death of all living things. The theory postulates that aging is caused by free radical reactions, i.e., these reactions may be involved in production of the aging changes associated with the environment, disease and the intrinsic aging process. The origination of the theory and its application to the problem of increasing the functional life span are discussed. Support for the free radical theory of aging has increased progressively and now includes: 1) studies on the origin of life and evolution, 2) studies on the effect of ionizing radiation on living things, 3) dietary manipulations of endogenous free radical reactions, 4) the plausible explanations it provides for aging phenomena, and 5) the growing numbers of studies that implicate free radical reactions in the pathogenesis of specific diseases. The rapidly growing number of scientists involved in studies on the role of free radical reactions in biological systems should assure future significant increases in the healthy, useful, life span of man.