Polyunsaturates and KCL to Control Mild Hypertension
Condition: Cardiovascular Diseases; Heart Diseases; Hypertension; Vascular Diseases
MeSH terms: Hypertension; Cardiovascular Diseases; Heart Diseases; Vascular Diseases
Study type: Interventional
Phase: Phase 2

Summary: 
      To test the efficacy of omega-3 fatty acids in untreated mild hypertensives and magnesium,
      calcium, and potassium supplementation supplementation in non-hypertensives. These clinical
      trials were conducted in sequence over a four year period.
    

Detailed description: 
      BACKGROUND:

      The hypothesis that omega-3 fatty acids as well as magnesium and potassium in the diet
      lowered blood pressure in mild hypertensives needed further documentation, although
      preliminary and less well controlled studies had suggested such an effect was possible. In a
      previous study the investigators did not find a hypotensive effect of another polyunsaturated
      fatty acid, linoleic acid. In addition, findings of lower blood pressures in vegetarians and
      results obtained from a study in which vegetarian diets were fed to normotensives led to the
      conclusion that dietary factors other then linoleic acid were responsible for the possible
      hypotensive effect of vegetarian diets. The nutrients which were selected for further study,
      omega-3 fatty acids, magnesium and potassium, occur in higher amounts in vegetarian diets.

      Dietary supplementation with fish oils had only been done in a few studies with inconclusive
      results. However, the relationship of omega-3 fatty acids to the synthesis of prostacyclins,
      which are locally active vasodilators and which decrease with the excretion of the
      vasoconstrictor thromboxane, provide a possible mechanism for an effect of these compounds on
      blood pressure.

      The role of potassium in the control of blood pressure was first suggested from
      cross-cultural studies in which populations consuming high levels of potassium displayed
      lower rates of hypertension and a decrease in blood pressure with age. Cohort studies within
      this country have also shown a relationship between potassium intake or the ratio of
      potassium and sodium, as measured by urinary excretion and blood pressure. Most constantly it
      found that blood pressure differences between blacks and whites have been related to
      differences in potassium excretion.

      The results from human experimental studies involving potassium supplementation in
      normotensives and hypertensives have indicated mixed effects but blood pressure lowering was
      most consistently observed in subgroups with a family history of hypertension or those with
      higher blood pressure.

      DESIGN NARRATIVE:

      Trial 1: Subjects were randomized to a fish oil treatment group of 6 or 12 grams/day of
      omega-3 fatty acids or to a placebo group. At the end of 12 and 24 weeks, participants in the
      three groups were crossed-over to one of the other two treatments for an additional 12 weeks.
      The primary outcome was clinic blood pressure on 3 days at the end of the treatment period.

      Trial 2: Subjects were randomly assigned to one of four treatments and placebo: magnesium
      supplementation; potassium supplementation; calcium supplementation; all 3 supplements;
      matching placebos. The trial was double-blinded. Each of the treatments was administered for
      six months with measurements taken at baseline and at the end. The primary outcome was
      24-hour ambulatory systolic BP.

      The study completion date listed in this record was obtained from the Query/View/Report (QVR)
      System.
    

Intervention name(s): mineral supplements; Trial 1: fatty acids, omega-3; Trial 2: Mineral supplements; dietary supplements
Intervention type(s): Dietary Supplement; Dietary Supplement; Behavioral
Allocation: Randomized
Intervention model: Crossover Assignment
Primary purpose: Treatment