Adequate intake of ascorbic acid, as a potent
antioxidant nutrient, is essential for proper health. This
nutrient interacts with the human immune system, by
supporting immune response and providing antioxidant
protection to exogenously derived and endogenously
generated ROS and help to avoid damaging effects to
surrounding tissues at the site of inflammation. Vitamin
C consumption decreases the risk of DNA damage in
the cells of the immune system, enhances antioxidant
defenses and increases T-cell responsiveness to
antigens. Inadequate intake of this antioxidant may result
in impaired function of immune cells and suppressed
immunity, which predisposes to infections and
aggravates malnutrition. Even vitamin C requirements
vary greatly among the individuals, it is suggested that
vitamin C supplementation is necessary to achieve
optimal health. Therefore, we advise healthy people to
consume vitamin C in order to ensure a proper function
of immune system. On the other hand, we are far from
being able to define the optimal levels of intake required
to maintain an optimal immune response and to prevent
or treat viral or other infectious diseases. Furthermore,
additional studies that aim to determine the exact clinical
benefit of high-dose ascorbic acid, as an antioxidant
therapy, should be encouraged while making a rational
assessment of its safety.