What Is the Strength of the Evidence for Supplement Use for a Healthy Immune System?

Both genetic and environmental factors are known to cause a decline of the immune system during aging.1 Attempts to prevent the loss of genome integrity and damage to cellular DNA in immune cells during aging are of vital importance. With age, cumulative damage caused by both exogenous and endogenous agents such as UV or ionizing radiation, and reactive oxygen species generated by respiration could further increase the damage to DNA, resulting in the impairment of immune function. Loss of various immunological functions in the elderly includes both changes in innate (rapid) and adaptive (delayed) immune responses, which are regulated closely by various lymphocyte subsets. With age, the loss of T-cell function, particularly changes in the naïve/memory T-cell ratio, occurs earlier than the loss of B cell function, which causes an imbalance in Th-1 (IL-2, IFN-γ) and Th-2 (IL-4, IL-6, IL-10) cytokines.2 These changes may promote either organ specific or systemic inflammation and an increase in autoimmune disorders in the elderly, including susceptibility to viral and bacterial infection. Inadequate nutrition and/or selective dietary deficiency in the elderly also could cause immune deficiency. Furthermore, early loss of immune function may lead to failure to ward off diseases of aging such as cardiovascular disease, cancer, and various autoimmune disorders such as arthritis and osteoporosis. Thus, ther