Vegetables, high nitrate foods, increased breath nitrous oxide.

We have demonstrated nitrous oxide (N2O), a metabolite of the reduction of nitrate (NO(3)-) by microflora, in exhaled air. The purpose of this study is to examine the effect of ingesting vegetables, which contain high levels of NO(3)-, on breath N2O levels. We measured breath N2O in six healthy subjects aged 20-41 years at 15-min intervals after the following: (1) no ingestion; (2) ingestion of 180 g of vegetable juice; and (3) ingestion of 50 g of lettuce. N2O levels were measured with an infrared-photoacoustic (IR-PAS) analyzer. N2O was detectable in all subjects regardless of treatment protocol. Lettuce and vegetable juice significantly increased breath N2O levels. Total excretions in breath N2O were significantly higher in the lettuce group (P = 0.028) and the vegetable juice group (P = 0.046) than controls. Breath N2O increases after vegetable ingestion, probably due to denitrification of NO(3)- by normal microflora in the intestinal tract.