The use of nitrites in food preservation is highly controversial due to the potential for the formation of nitroso-compounds such as nitrosamines, N-Nitrosamides and nitrosyl-heme. When the meat is cooked at high temperatures, nitrite-cured meat products can also lead to the formation of nitrosamines. The effect is seen for red processed meat, but not for white meat or fish. Nitrates and nitrites may cause cancer and the production of carcinogenic nitrosamines can be potently inhibited by the use of the antioxidants Vitamin C and the alpha-tocopherol form of Vitamin E during curing. Under simulated gastric conditions, nitrosothiols rather than nitrosamines are the main nitroso species being formed. The use of either compound is therefore regulated; for example, in the United States, the concentration of nitrates and nitrites is generally limited to 200 ppm or lower.