Associations between dietary salt, potassium and blood pressure in South African adults: WHO SAGE Wave 2 Salt & Tobacco

Nutr Metab Cardiovasc Dis. 2017 Sep;27(9):784-791. doi: 10.1016/j.numecd.2017.06.017. Epub 2017 Jul 8.

Abstract

Background & aims: In June 2016, South Africa implemented legislation mandating maximum sodium levels in a range of processed foods with a goal of reducing population salt intake and disease burden from hypertension. Our aim was to explore the relationship between salt and blood pressure (BP) in a subsample of the World Health Organization Study on global AGEing and adult health (SAGE) Wave 2 before implementation of legislation in South Africa.

Methods & results: Blood pressure (BP) was measured in triplicate (n = 2722; median age 56 years; 33% male) and 24-h urine collected in a nested subsample (n = 526) for sodium, potassium and creatinine analysis. Hypertension prevalence was 55% in older adults (50-plus years) and 28% in younger adults (18-49 years). Median salt intake (6.8 g/day) was higher in younger than older adults (8.6 g vs 6.1 g/day; p < 0.001), and in urban compared to rural populations (7.0 g vs 6.0 g/day; p = 0.033). Overall, 69% of participants had salt intakes above 5 g/day. Potassium intakes were generally low (median 35 mmol/day) with significantly lower intakes in rural areas and older adults. Overall, 91% of adults failed to meet the daily potassium recommendation of 90 mmol/d. Salt intakes above 5 g/day, and to a greater extent, a dietary sodium-to-potassium (Na:K) ratio above 2 mmol/mmol, were associated with significantly steeper regression slopes of BP with age.

Conclusion: These preliminary results indicate that high dietary Na:K ratio may lead to a greater increase in BP and hypertension risk with age. Interventions to increase potassium intakes alongside sodium reduction initiatives may be warranted.

Keywords: Aging; Health policy; Hypertension; Potassium; Public health; Salt; Sodium; South Africa.

Publication types

  • Comparative Study

MeSH terms

  • Adolescent
  • Adult
  • Age Distribution
  • Aged
  • Blood Pressure*
  • Diet, Sodium-Restricted
  • Female
  • Health Status
  • Humans
  • Hypertension / diagnosis
  • Hypertension / epidemiology*
  • Hypertension / physiopathology
  • Hypertension / prevention & control
  • Linear Models
  • Male
  • Middle Aged
  • Potassium Deficiency / diagnosis
  • Potassium Deficiency / epidemiology*
  • Potassium Deficiency / urine
  • Potassium, Dietary / administration & dosage*
  • Potassium, Dietary / urine
  • Prevalence
  • Protective Factors
  • Recommended Dietary Allowances
  • Risk Assessment
  • Risk Factors
  • Risk Reduction Behavior
  • Rural Health
  • Sodium, Dietary / adverse effects*
  • Sodium, Dietary / urine
  • South Africa / epidemiology
  • Urban Health
  • Young Adult

Substances

  • Potassium, Dietary
  • Sodium, Dietary