EFFECT OF DIETARY NITRATE SUPPLEMENTATION ON PLASMA NITRATE/NITRITE IN PHYSICALLY ACTIVE MEN

Beetroot juice (BJ) has been reported to improve certain aspects of exercise performance, which may be linked to increased nitric oxide, which blood levels are connected with plasma nitrates and nitrites. The aim of this study was to investigate the effect of dietary nitrate supplementation by BJ on plasma nitrate/nitrite. In two separate experiments, eighteen healthy males, who were active in sporting activities, volunteered to participate in this study. BJ supplementation or placebo (PL) were taken 6 days in a row. Blood samples were taken in 4th, 5th, and 6th day, 2 hours after (first experiment) or 4 hours (second experiment) BJ or PL consumption. Blood samples were drawn from vena cubiti, after a five-minute rest in the half-sitting position into S-Monovette lithium heparin tubes (2.7 ml). Plasma samples were separated in a cooled centrifuge. Nitrate and nitric plasma levels were determined by a commercially available nitrate/nitrite colorimetric assay kit (Cayman Chemical) in samples stored at-80 degrees C. Levels of plasma nitrates were in all experimental situations (4th-6th day) and in all measured subjects higher after BJ supplementation in comparison to PL (p = 0.0007-0.00002). On the other side, plasma nitrites have not changed significantly after BJ consumption. 5th and 6th day of BJ supplementation 2 hours before testing, average of plasma nitrites and plasma nitrites were lower in most of subjects in comparison to PL. BJ supplementation 4 hours before testing showed increase of plasma nitrites in all experimental situations and in most of subjects. However difference was not significant in all measured days (p = 0.670; 0.145; 0.056). Our data indicates that ingestion of BJ significantly increased plasma nitrates, but plasma nitrites have not been influenced significantly. Certain differences have been ascertained depending on time consumption. The authors discuss the possible causes of these results.