Normal plasma vitamin C concentration is 50 µmol/L. Plasma ascorbate concentrations above 10 µmol/L but below 50 µmol/L represent a status with an increased risk of insufficiency. Scurvy appears when the plasma concentration falls below 10 µmol/L, which corresponds to an intake of less than 10 mg vitamin C/day and a body pool less than 300 mg [60]. It is acknowledged that vitamin C concentration declines during stress and infection, particularly in leukocytes, as it is used to protect host cells against the oxidative stress [46]. For the same reason, children exposed to smoking or environmental tobacco smoke require increased intake of vitamin C [44].