dietary sodium; dietary Na+; dietary salt

Epidemiology

• foods contributing to dietary sodium in the US
  • bread & rolls > cold cuts > pizza > poultry > soups > sandwiches > cheese > pasta mixed dishes > meat mixed dishes > savory snacks
• 2/3 of dietary sodium comes from foods purchased at stores; the remainder comes from restaurants, cafeterias ...
• 90% of school-aged children eat more than recommended daily allowance of sodium (< 2300 mg/day)
  • on the average, school-age children consume 3300 mg/day
• 90% of Americans consume excess dietary salt
• decline in sodium content of packaged food & beverages 2000- 2014 ~ 400 mg daily per person
• estimated mean dietary sodium intake is 3608 mg/day

Dosage

• < 2300 mg/day in young individuals
• < 2000 mg/day for adults (WHO)
• < 2300 mg/day for persons age >- 14 years (USDA, HHS)
• 1500 mg/day for people with hypertension, > age 40, or African Americans
• see DASH diet
• 3000 mg/day may be optimal for healthy people

Adverse effects

• high Na+ intake associated with increased mortality in overweight, but not normal weight patients
  • increased risk of stroke
  • increased risk of myocardial infarction
  • increased all-cause mortality
• higher Na+ intake is associated coronary atherosclerosis & carotid atherosclerosis
• excessive dietary salt may contribute to progression of cerebral small vessel disease in older adults
  • effects of salt may be mediated in part by hypertension
• sodium intake is not significantly associated with mortality or development of cardiovascular disease or heart failure in elderly 71-80 years of age
• high Na+ intake in patients with chronic renal failure is associated with increased risk for cardiovascular events
• low urine sodium excretion may be associated with increased risk of cardiovascular mortality
• hypertension
  • reduction is systolic BP of 1.1 mm Hg & diastolic BP of 0.6 mm Hg by sodium restriction unlikely to be helpful for hypertension in general
  • age & race may play a role in the effects of dietary sodium on hypertension
  • increase in systolic BP & diastolic BP with increased sodium intake > 3 g/day
  • increase in systolic BP due to sodium < 13 mm Hg
  • dietary salt decreases intestinal Lactobacilli in mice & humans & increases blood pressure
• salt added to food increases risk of chronic kidney disease (11%)
• in culture, human CD4 cells exposed to increasing amounts of NaCl result in a dose-dependent increase in IL-17, an inflammatory mediator linked to multiple sclerosis, psoriasis & other autoimmune disorders

Laboratory

• 24 hour urine sodium
  • 90% of dietary sodium is excreted in the urine

Management

• lower salt intake
  • lowers blood pressure regardless of baseline blood pressure, sex, or race
    • 4.3 mm Hg drop in systolic blood pressure
    • 5.6 mm Hg drop in systolic blood pressure for every 100 mmol/day reduction in urinary sodium excretion (87 mmol/day corresponds to 2 g/day), corresponding drop in diastolic BP is 2.3 mm Hg
    • relationship of sodium intake & systolic blood pressure is linear
    • average 8 mm Hg lower systolic blood pressure vs high sodium diet
    • 12 mm Hg drop in systolic BP for 1 gram of sodium vs 6 grams/day
      • corresponding drop for diastolic BP 5 mm Hg
  • no significant adverse physiological effect
  • may reduce risk of stroke via lower blood pressure
  • associated with 15% lower (but not statistically significant) 20 year mortality in prehypertensive adults
  • very low sodium intake is not associated with mortality
• FDA announced draft guidance for voluntarily reducing sodium in processed & restaurant food
  • 2-year target aims to reduce sodium intake to 3000 mg/day
  • 10-year target aims for sodium intake < 2300 mg/day, following the Dietary Guidelines for Americans' recommendation
  • people age >= 14 years should reduce sodium intake to < 2300 mg/day
• sodium restriction may be most beneficial in communities with the highest sodium consumption
• moderate sodium (3-5 g/day) & high potassium intake (> 2.1 g/day) associated with lowest cardiovascular mortality
• reducing sodium intake does not improve outcomes in patients with chronic heart failure
• salt substitute (70% sodium chloride, 30% potassium chloride) to replace regular salt lowers systolic blood pressure 3.3 mm Hg assessed at year 5
  • salt substitute significantly lowers risk of stroke & all-cause mortality
• lower urine sodium & higher urine potassium associated with fewer adverse cardiovascular events

Comparative biology

• in mice, excess dietary salt inhibits resting cerebral perfusion & endothelial function, leading to cognitive impairment
  • effect depends on expansion of TH17 cells in small intestine, resulting in an increase in plasma IL-17
  • IL-17 facilitates Rho-kinase dependent inhibitory phosphorylation of endothelial nitric oxide synthase reducing nitric oxide production in cerebral endothelial cells

More general terms

• nutritional (essential) mineral

Additional terms

• Dietary Approaches to Stop Hypertension (DASH) diet
• low sodium diet; Na+ restriction
• Na+