Nitrosamines blocking

Other conditions previously mentioned in this chapter, such as cancer, immunocompetence and interferon production, antihistamine eflFects in colds, increased iron absorption, eflFects on cholesterol metabolism, and nitrosamine blocking, were studied at higher than RDA dosage levels. These many situations require additional research study to determine what the minimum levels are to attain the optimal health condition. 

Evidence exists that the relative solubility of amines and inhibitors in heterogeneous oil-water systems could be decisive in formation of nitrosamines and blocking these reactions, Nitrosopyrrolidine formation in bacon predominates in the adipose tissue despite the fact that its precursor, proline, predominates in the lean tissue (5,6,7). Mottram and Patterson (8) partly attribute this phenomenon to the fact that the adipose tissue furnishes a medium in which nitrosation is favored, Massey, et al, (9) found that the presence of decane in a model heterogeneous system caused a 20-fold increase in rate of nitrosamine formation from lipophilic dihexylamine, but had no effect on nitrosation of hydrophilic pyrrolidine. Ascorbic acid in the presence of decane enhanced the synthesis of nitrosamines from lipophilic amines, but had no effect on nitrosation of pyrrolidine. The oil-soluble inhibitor ascorbyl palmitate had little influence on the formation of nitrosamines in the presence or absence of decane. 

Indeed, given an improperly designed or understood system, a blocking agent, like ascorbic acid, could be catalytic toward nitrosamine formation. For example, if the source of nitrosatlng agent is nitrite ion and the susceptible amine is in the lipid phase, conceivably ascorbic acid could cause the rapid reduction of nitrite ion to nitric oxide which could migrate to the lipid phase. Subsequent oxidation of NO to NO in the lipid phase could cause nitrosation. 

Aside from ascorbic acid and alpha-tocopherol, which have been shown to be effective blocking agents, there are other factors which appear important in blocking nitrosamine formation... 

Ascorbic acid and alpha-tocopherol are effective blocking agents against N-nitroso compound formation. Ascorbic acid is effective particularly in aqueous media, and tocopherol effective particularly in lipid phases. They should be used in conjunction due to the mutually complementary actions of the two vitamins in blocking nitrosamine formation in both aqueous and lipid media. 

In addition to vitamin C and vitamin E as effective blocking agents, there are other substances which also are capable of preventing nitrosamine formation which are present in normal foods. The influence of this factor on the design of experimental studies should not be overlooked. 

If the concepts and facts presented in this paper are correct, a major kind of human cancer in many regions of the world, cancer of the stomach, is due to a type of nitroso compound, a nitrosoureido derivative, even though not a nitrosamine It is quite certain that the formation of such compounds can be blocked by vitamin C and vitamin E, as well as by some other substances such as gallates Thus, the primary prevention of cancer caused by nitroso compounds is readily accomplished through an adequate Intake of such harmless inhibitors with every meal from infancy onwards ... 

E lipid-soluble antioxidant, prevents lipid oxidation of membranes, needed for healthy blood cells and tissues, blocks nitrosamine formation, protects PUFAs from autoxidation, important for normal immune fimction neuromuscular disorders, red blood ceU mpture (both uncommon) reduces risk of chronic disease (cardio-vascular, precancerous lesions, cancer), immunoenhancement, protec-tion from exercise-induced muscle injury, improves metaboHc control, re-duces risk of compHcations in diabetes... 

Femlic acid is also a potential anticarcinogen [98], blocking nitrosamine formation in gastric fluid [99],... 

Three cases that demonstrate the value of additional research are the eflFects of smoking on the rate of ascorbic acid metabolism, as described in chapter 16 in this book the increase in the RDA for vitamin C in 1980 over that in 1974 on the basis of the significant improvement in iron absorption (40) and the blocking of nitrosamine production as described in chapter 24 in this book. 

The nitrosation of several secondary and tertiary amines can be blocked in vitro by the addition of vitamin C. The vitamin appears to compete for the nitrite, thus inhibiting nitrosation. It has been demonstrated that vitamin C does not react with amines, nor does it enhance the rate of nitrosamine decomposition. However, it reacts very rapidly with nitrite and nitrous acid. It has been suggested that the vitamin decreases the available nitrite by reducing nitrous acid to nitrogen oxides, leading to inhibition of the nitrosation reaction ... 

Lastly, but importantly, in a chapter titled Chemical Carcinogenesis, the following cited authors note that vitamin C inhibits carcinogenesis in the stomach by blocking the formation of nitrosamines from the nitrosation of amines (Williams and Weisberger, in Amdur et al.,1991, p. 146). This is aside from the usual view of medical orthodoxy that vitamin C has no special therapeutic effects other than the alleviation of scurvy (e.g., Marcus and Coulston, in Pharmacological Basis of Therapeutics, pp. 1568-1571). 

Newmark, H.L., and Mergens, W.J., 1981, Blocking nitrosamine formation using ascorbic acid and a-tocopherol, "Gastro-... 

The antioxidant properties of ascorbate are often cited as the primary factor underlying associations of the vitamin with decreased cancer risk (Gershoff, 1993 Block, 1992) and mortality (Enstrom et al., 1992). However, other actions of the vitamin may also play a part, including enhanced immunocompetence and inhibition of carcinogenic nitrosamine formation. 

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