Sodium

• Oral Rehydration Salts (or Solutions) (ORS)


  Clean water + electrolytes + glucose
• Replacing lost fluid
• Replacing lost fluid


  • Example 1: Hot yoga (Bikram)
  • Example 2: Food poisoning
  • Example 3: Very sick child/elderly adult in NZ
  • Example 4: Very sick child in rural Africa/SA
• Severity and patient
• Options for replacing lost fluid

  • Water
  • Food
  • ORS (clean water + electrolytes + glucose)
  • Zinc
• Options for treating dehydration

  • Treat at home
  • Treat medically
• On average, how does the sodium intake of the typical NZ diet compare to the what we need to consume?

  
• What foods are high in sodium?

  
• What foods contribute the greatest amount of sodium in the typical NZ diet?

  
• What is the best way to measure sodium intake?

  
• Do we need to add salt to food?
• What happens if you eat too much sodium over a lifetime?
• Minerals and Trace Elements

  • Essential, non-organic elements
  • Do not provide energy
  • If absent or low in the diet, symptoms of deficiency may appear
  • Required in the diet in small amounts i.e. μg or mg
  • Bioavailability = amount absorbed and used
• Minerals

  • Na, K, Ca, Mg, Cl
• Trace Elements


  • Fe, Zn, I, Fl, Se, Cr
• Quantity in body


  Minerals: >5 grams

  Trace Elements: <5 grams
• Sodium in the diet: 10% inherent, ?? % discretionary, ?? % processing

  
• Sodium from discretionary salt: NZ

  
• Sodium in the diet: 10% inherent, 13% discretionary, ~75% processing

  
• Sodium in the diet: 10% inherent, 13% discretionary, ~75% processing (pork 71 mg/100 g vs bacon 2100 mg/100g)

  
• NRVs for NZ/Australia: Adequate Intake (AI) is 460-920 mg/day ® day to day needs, Suggested Dietary Target (SDT) <2000 mg/day ® chronic disease
• Sodium


  Absorption: Well absorbed, not regulated

  Plasma levels controlled by kidney

  Function: Principal cation in ECF, Primary regular of ECF volume, Maintain acid-base balance, Nerve impulse transmission, Muscle contraction

  Excretion: Urine: >90% sodium excreted in urine, Sweat

  Deficiency: Rare from diet, Depletion from losses (eg., sweat, diarrhoea, vomiting)

  Toxicity?: Acute is rare, "Chronic" is common.

  
• Kidney's capacity to excrete sodium declines with age: GFR declines from age 30 yr, 40% at 80yr, Smaller increases in salt intake, increased BP
• Hypertension


  A disease whereby someone has higher than normal blood pressure

  High blood pressure can damage blood vessels increasing risk of heart disease renal disease
• Causes of hypertension


  • Genetics

  Age: ­ age, ­ BP

  Weight: ­ BMI, ­ BP

  Smoking

  Exercise: ­ exercise, ¯ BP

  Stress

  Diet: alcohol, caffeine, sodium, potassium, calcium, magnesium
• A lifetime of eating lots of salt!
• Global Burden of Disease Study 2017
• Before 1988: Numerous small studies, Dietary sodium, Lack of standardisation
• Then...: INTERSALT (1988), Meta-analysis by Law et al (1991), DASH 1 (1997), DASH 2 (DASH sodium) (2001)
• INTERSALT (1988): 52 countries (200 people/country), Na excretion (24 hr), BP µ weight, alcohol, age, sodium
• Meta-analysis (1991): Of 78 trials, ¯2300 mg/day in Na, small¯ in BP, Twice as effective in older people
• DASH 1 (Dietary Approaches to Stop Hypertension): Clinical intervention trial, Randomly placed in three diet groups: 1. Control diet, 2. Fruits and vegetables diet, 3. Fruits and vegetables + low fat dairy products diet, All foods prepared for subjects, Energy intake, protein, CHO, at similar levels for all three groups, 3 week run-in, 8 weeks on diet
• DASH 2: Clinical Intervention trial, Two diet groups at three levels of sodium: 1. Control diet, 2. DASH diet, Two week run-in, random 30 day crossover at each level of sodium on either control or DASH diet