title: Plasma nitrate and nitrite are increased by a high-nitrate supplement but not by high-nitrate foods in older adults.
abstract: Little is known about the effect of dietary nitrate on the nitrate/nitrite/nitric oxide cycle in older adults. We examined the effect of a 3-day control diet vs high-nitrate diet, with and without a high-nitrate supplement (beetroot juice), on plasma nitrate and nitrite kinetics and blood pressure using a randomized 4-period crossover controlled design. We hypothesized that the high-nitrate diet would show higher levels of plasma nitrate/nitrite and lower blood pressure compared with the control diet, which would be potentiated by the supplement. Participants were 8 normotensive older men and women (5 female, 3 male, 72.5 ± 4.7 years old) with no overt disease or medications that affect nitric oxide metabolism. Plasma nitrate and nitrite levels and blood pressure were measured before and hourly for 3 hours after each meal. The mean daily changes in plasma nitrate and nitrite were significantly different from baseline for both control diet + supplement (P < .001 and P = .017 for nitrate and nitrite, respectively) and high-nitrate diet + supplement (P = .001 and P = .002), but not for control diet (P = .713 and P = .741) or high-nitrate diet (P = .852 and P = .500). Blood pressure decreased from the morning baseline measure to the three 2-hour postmeal follow-up time points for all treatments, but there was no main effect for treatment. In healthy older adults, a high-nitrate supplement consumed at breakfast elevated plasma nitrate and nitrite levels throughout the day. This observation may have practical utility for the timing of intake of a nitrate supplement with physical activity for older adults with vascular dysfunction.
authors.affiliation: Department of Health and Exercise Science, Wake Forest University, Winston-Salem, North Carolina 27109-7868, USA. millergd@wfu.edu
authors.forename: Gary D
authors.initials: GD
authors.lastname: Miller
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Marsh
authors.forename: Robin W
authors.initials: RW
authors.lastname: Dove
authors.forename: Daniel
authors.initials: D
authors.lastname: Beavers
authors.forename: Tennille
authors.initials: T
authors.lastname: Presley
authors.forename: Christine
authors.initials: C
authors.lastname: Helms
authors.forename: Erika
authors.initials: E
authors.lastname: Bechtold
authors.forename: S Bruce
authors.initials: SB
authors.lastname: King
authors.forename: Daniel
authors.initials: D
authors.lastname: Kim-Shapiro
mesh_terms: D000368:Aged; D027461:Beta vulgaris / Q000737:chemistry*; D001794:Blood Pressure / Q000187:drug effects*; D018592:Cross-Over Studies; D004032:Diet; D019587:Dietary Supplements; D005260:Female; D006801:Humans; D008297:Male; D009566:Nitrates / Q000097:blood / Q000494:pharmacology*; D009569:Nitric Oxide / Q000378:metabolism; D009573:Nitrites / Q000097:blood*; D028321:Plant Preparations / Q000494:pharmacology*; D018517:Plant Roots; D012016:Reference Values
chemical_list: D009566:Nitrates; D009573:Nitrites; D028321:Plant Preparations; D009569:Nitric Oxide