Discussion Until recently, it has been commonly agreed that NO in vivo could only be synthesised by NOS with nitrite and nitrate as inert biological end-products of NO metabolism. However, it was demonstrated in 1994, that nitrite derived from dietary nitrate was a substrate for NOS-independent generation of NO in the acidic condition of the human stomach [8] and [9]. Despite the demonstration of a pharmacological role for nitrite in vascular and immune function, the potential health aspects of food sources of nitrates and nitrites have not received much attention [22].