V i t a m i n C
Vitamin C is a cofactor in at least eight enzymatic reactions, including several collagen synthesis reactions performing numerous functions in the human body. These include the synthesis of collagen, neurotransmitters and synthesis and catabolism of tyrosine as well as the metabolism of microsome.
Moreover, vitamin C plays an important role in the synthesis of several important peptide hormones, neurotransmitters and carnitine.
Vitamin C is required for the synthesis of collagen, the intercellular substance which gives structure to muscles, vascular tissues, bones, gums, blood vessels, tendons and ligaments. Due to these functions, vitamin C – especially in combination with zinc – is also important for the healing of wounds. Combinations of antioxidants improve wound healing.
It does act as a reducing agent, donating electrons to various enzymatic and a few non-enzymatic reactions. In this way regenerating other antioxidants such as vitamin E.
Vitamin C improves iron absorption and resistance to infection, as it is found in high concentrations in immune cells, and is consumed quickly during infections. Acting also as an inhibitor of histamine, a compound that is released during allergic reactions.
Furthermore, vitamin C is vital for the cardiovascular system. It's antioxidant properties are absorbed into the blood stream, and can actually repress the accumulation of arterial plaque, cleaning the arteries and enabling a healthy flow of blood to the heart.
It has been shown that smokers who have diets poor in vitamin C are at a higher risk of lung-borne diseases than those smokers who have higher concentrations of vitamin C in the blood.
90 mg RDA - 2000 mg UL
RDA (recommanded dietary allowances) per day 
UL (tolerable upper intake level) per day 
 Food and Drug Administration (FDA)
 Dietary Reference Intakes: Tolerable Upper Intake Levels, Food and Nutrition Board, Institute of Medicine, National Academies, 1997