title: Sodium-rich carbonated natural mineral water ingestion and blood pressure.
abstract: BACKGROUND
  There is a strong positive correlation between sodium chloride intake and hypertension. In industrialized countries the ingestion of carbonated and non-carbonated mineral water is an important source of calorie-free fluids. The mineral content of these waters varies greatly, with many brands containing high levels of sodium. However, some mineral waters contain greater amounts of bicarbonate instead of chloride as the anion associated with the sodium cation. This is relevant because it is well established that the effect of sodium on blood pressure depends on the corresponding anion. Additionally the pressor effect of sodium bicarbonate is much lower than that of equivalent amounts of sodium chloride. The aim of our work was to evaluate the effect of ingesting a sodium-rich carbonated mineral water (Agua das Pedras) on blood pressure values in normotensive individuals.
  
  
  METHODS
  This crossover, non-blinded study evaluated 17 individuals (9 female and 8 male), aged 24-53 years, median body mass index (BMI) < 23, randomly allocated in two groups, ingesting 500 ml/day of Agua das Pedras or Agua Vitalis. Each arm of the study lasted 7 weeks, with 6 weeks of washout between them. Twenty-four hour urinary samples were collected at the beginning and end of each arm to determine pH and sodium and potassium excretion. Blood pressure and body weight were measured weekly throughout the study. A mixed-effects model was used to compare groups (p < 0.05). The Wilcoxon test was used to analyze electrolyte excretion.
  
  
  RESULTS
  No differences were observed in blood pressure values between treatments or from baseline values. We found a positive correlation between BMI and blood pressure.
  
  
  CONCLUSIONS
  The daily ingestion of 500 ml of Agua das Pedras had no effect on blood pressure. A study by Schorr and co-workers found that the ingestion of bicarbonate-rich water (1.5 l/day) had hypotensive effects in an elderly population. However, these results should be verified in hypertensive subjects, who are more likely to be salt sensitive, since in some of these individuals blood pressure rises even when sodium is ingested as sodium bicarbonate.
authors.affiliation: Serviço de Bioquímica (U38/FCT), Faculdade de Medicina, Universidade do Porto, Porto, Portugal. alejandrosantos@fcna.up.pt
authors.forename: Alejandro
authors.initials: A
authors.lastname: Santos
authors.forename: Maria João
authors.initials: MJ
authors.lastname: Martins
authors.forename: João Tiago
authors.initials: JT
authors.lastname: Guimarães
authors.forename: Milton
authors.initials: M
authors.lastname: Severo
authors.forename: Isabel
authors.initials: I
authors.lastname: Azevedo
mesh_terms: D000328:Adult; D001794:Blood Pressure / Q000187:drug effects*; D002254:Carbonates / Q000494:pharmacology*; D018592:Cross-Over Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008900:Mineral Waters; D055815:Young Adult
chemical_list: D002254:Carbonates; D008900:Mineral Waters; C005686:sodium carbonate