FORMATION OF NITROSAMINES DURING CONSUMPTION OF NITRATE-RICH AND AMINE-RICH FOODS, AND THE INFLUENCE OF THE USE OF MOUTHWASHES

We studied the formation of carcinogenic nitrosamines during consumpti on of food rich in nitrate and amines, and its possible inhibition by use of an antibacterial mouthwash. Twelve volunteers were fed a diet c ontaining the high-nitrate vegetables lettuce or spinach during two pe riods of four consecutive days, in combination with fish products cont aining high levels of amines as nitrosatable precursors. During the tw o periods, the subjects used an antibacterial mouthwash containing chl orhexidine or a control mouthwash without antibacterial activity. Twen ty-four-hour urine samples were collected after consumption of the mea ls, and saliva samples were collected 1 h after each meal. The nitrate and nitrite contents of the urine and saliva samples were determined by spectrophotometry (for nitrite) and HPLC (for nitrate). The concent rations of volatile nitrosamines in the urine samples were determined by gas chromatography-mass spectrometry. Significant increases in mean urinary nitrate levels (from 59 to 135 mg/24 h) and in mean salivary nitrate levels (from 10 to 56 mu g/ml) and salivary nitrite levels (fr om 2 to 11 mu g/ml) were observed during the consumption of food rich in nitrate and amines, as well as a significant increase in the mean u rinary excretion of total examined volatile nitrosamines (from 2 to 7 nmol/24 h) and of N-nitrosodimethylamine (from 1.2 to 2.9 nmol/24 h). Use of the antibacterial mouthwash resulted in a decrease in mean sali vary nitrite levels from 16 to 3 mu g/ml and a decrease in mean urinar y excretion of N-nitrosomorpholine (from 7.0 to 0.3 nmol/24 h). For th e whole data set, significant correlations were observed between nitra te intake in food and urinary nitrate (p = 0.01; r(2) = 0.07) and betw een urinary nitrate and urinary N-nitrosodimethylamine (p = 0.002; r(2 ) = O.11). In conclusion, consumption of a diet rich in nitrate and am ines increases the risk of formation of carcinogenic nitrosamines. Use of an antibacterial mouthwash containing chlorhexidine can result in inhibition of nitrosamine formation.