Grand Rounds

Potassium and Sodium Intake: Do the WHO Recommendations Have it Right?

BACKGROUND AND PURPOSE:

The WHO recommends an extremely low sodium intake but high potassium intake
- Recommendations: <2.0 g sodium | >3.5 g potassium
- Current averages: 4 g/day for salt and 2g/day for potassium
Sodium and potassium are interdependent
- Sodium: Many prospective studies demonstrate a ‘J curve’ for sodium where both low and high sodium may be more highly associated with adverse outcomes (in those without hypertension)
- Potassium: Linear reduction in BP and adverse CVD events with increasing potassium intake
O’Donnell et al. (BMJ, 2019) sought to determine the joint association of sodium and potassium with CVD and mortality

International prospective cohort study
- Prospective Urban Rural Epidemiological (PURE) Study
- High, middle, and low-income countries; urban and rural areas
Participants provided morning fasting urine samples
- 24 hour urinary sodium and potassium excretion (surrogates for intake)
Primary outcome: Composite of
- All cause mortality | Myocardial infarction | Stroke | Heart failure
Secondary outcomes
- Individual components of the composite primary outcome
- New diagnosis of cancer on follow-up
Reference categories
- Sodium excretion: 4.00 to 4.99 g/day
- Potassium excretion: <1.5 g/day
6 category variable for joint sodium and potassium
- sodium excretion
  - low: <3 g/day
  - Moderate:3-5 g/day
  - High: >5 g/day
- Potassium excretion
  - (1) ≥ or (2) < than median 2.1 g/day for each of the above

103,570 people participated
Mean estimated excretion
- Sodium excretion: 4.93 g/day
- Potassium: 2.12 g/day
After a median follow-up of 8.2 years
- 7884 (6.1%) participants had died or experienced a major cardiovascular event
A J-shaped association was observed of sodium excretion
Increasing potassium excretion inversely associated with death and cardiovascular events
The lowest risk of death and CVD
- Moderate sodium excretion (3-5 g/day) and
- Higher potassium excretion
The highest risk of death and CVD
- Low potassium and low sodium excretion
  - Hazard ratio (HR) 1.23 (95%CI, 1.11 to 1.37)
- Low potassium and high sodium excretion
  - HR 1.21 (95%CI, 1.11 to 1.32)
Next highest risk was for the following groups with potassium excretion greater than the median
- Low sodium excretion: HR 1.19 (95% CI, 1.02 to 1.38)
- High sodium excretion: HR 1.10 (95% CI, 1.02 to 1.18)
Higher potassium excretion diminished the increased cardiovascular risk associated with high sodium excretion (P for interaction=0.007)

Moderate sodium intake (3-5 g/day) with high potassium intake (foods such as fruit, vegetables, nuts) is associated with the lowest risk of mortality and cardiovascular events
Authors point out that feasibility of very low salt diets are limited, and that moderate salt intake may not only be more realistic but may be associated with better diet quality
Studies which focused on increasing potassium based foods with less focus on low sodium intake, demonstrated a significant reduction in CVD and mortality

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