title: Influence of iodide ingestion on nitrate metabolism and blood pressure following short-term dietary nitrate supplementation in healthy normotensive adults.
abstract: Uptake of inorganic nitrate (NO3-) into the salivary circulation is a rate-limiting step for dietary NO3-metabolism in mammals. It has been suggested that salivary NO3-uptake occurs in competition with inorganic iodide (I-). Therefore, this study tested the hypothesis that I-supplementation would interfere with NO3-metabolism and blunt blood pressure reductions after dietary NO3-supplementation. Nine healthy adults (4 male, mean ± SD, age 20 ± 1 yr) reported to the laboratory for initial baseline assessment (control) and following six day supplementation periods with 140 mL·day-1NO3--rich beetroot juice (8.4 mmol NO3-·day-1) and 198 mg potassium gluconate·day-1(nitrate), and 140 mL·day-1NO3--rich beetroot juice and 450 μg potassium iodide·day-1(nitrate + iodide) in a randomized, cross-over experiment. Salivary [I-] was higher in the nitrate + iodide compared to the control and NIT trials (P < 0.05). Salivary and plasma [NO3-] and [NO2-] were higher in the nitrate and nitrate + iodide trials compared to the control trial (P < 0.05). Plasma [NO3-] was higher (474 ± 127 vs. 438 ± 117 μM) and the salivary-plasma [NO3-] ratio was lower (14 ± 6 vs. 20 ± 6 μM), indicative of a lower salivary NO3-uptake, in the nitrate + iodide trial compared to the nitrate trial (P < 0.05). Plasma and salivary [NO2-] were not different between the nitrate and nitrate + iodide trials (P > 0.05). Systolic blood pressure was lower than control (112 ± 13 mmHg) in the nitrate (106 ± 13 mmHg) and nitrate + iodide (106 ± 11 mmHg) trials (P < 0.05), with no differences between the nitrate and nitrate + iodide trials (P > 0.05). In conclusion, co-ingesting NO3-and I-perturbed salivary NO3-uptake, but the increase in salivary and plasma [NO2-] and the lowering of blood pressure were similar compared to NO3-ingestion alone. Therefore, increased dietary I-intake, which is recommended in several countries worldwide as an initiative to offset hypothyroidism, does not appear to compromise the blood pressure reduction afforded by increased dietary NO3-intake.
authors.affiliation: Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, UK. Electronic address: S.Bailey2@lboro.ac.uk.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Bailey
authors.affiliation: Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, UK.
authors.forename: Jamie R
authors.initials: JR
authors.lastname: Blackwell
authors.affiliation: Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, UK.
authors.forename: Lee J
authors.initials: LJ
authors.lastname: Wylie
authors.affiliation: Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, UK.
authors.forename: Annabelle
authors.initials: A
authors.lastname: Emery
authors.affiliation: Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, UK.
authors.forename: Ellie
authors.initials: E
authors.lastname: Taylor
authors.affiliation: University of Exeter Medical School, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, UK.
authors.forename: Paul G
authors.initials: PG
authors.lastname: Winyard
authors.affiliation: Sport and Health Sciences, College of Life and Environmental Sciences, St. Luke's Campus, University of Exeter, Heavitree Road, Exeter, UK.
authors.forename: Andrew M
authors.initials: AM
authors.lastname: Jones
mesh_terms: D062186:Arterial Pressure / Q000187:drug effects; D027461:Beta vulgaris; D001794:Blood Pressure / Q000187:drug effects*; D019587:Dietary Supplements; D005260:Female; D000067030:Fruit and Vegetable Juices; D006801:Humans; D007454:Iodides / Q000008:administration & dosage / Q000378:metabolism*; D008297:Male; D009566:Nitrates / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*; D009573:Nitrites / Q000097:blood / Q000378:metabolism; D012463:Saliva / Q000378:metabolism; D055815:Young Adult
chemical_list: D007454:Iodides; D009566:Nitrates; D009573:Nitrites
keywords: Entero-salivary circulation; Nitric oxide; Nitrite; Nutrition; Vascular health