EAT FOR HEALTH Australian Dietary Guidelines

EAT FOR HEALTH – AusTRALiAn diETARy guidELinEs

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Guideline 3

3.2.2 The evidence for ‘limit intake of foods and drinks containing added salt’

The evidence for the guideline recommendation focuses on dietary sodium intake, rather than salt intake, because

most studies forming the body of evidence statements measured total sodium intake or urinary sodium excretion

(which is a marker of sodium intake from all sources including salt, other additives containing sodium, and

naturally occurring sodium).

Table 3.4: Evidence statements for ‘limit intake of foods and drinks containing added salt’

Evidence statement Grade

Decreasing consumption of sodium decreases blood pressure in normotensive adults; a reduction of 1,800 mg reduces

systolic blood pressure by about 2 mmHg and diastolic blood pressure by about 1 mmHg.

A

Decreasing consumption of sodium decreases blood pressure in hypertensive adults; a reduction of 1,800 mg reduces

systolic blood pressure by about 5 mmHg and diastolic blood pressure by about 3 mmHg. A

Consuming a diet low in sodium reduces blood pressure in children up to 18 years of age. B

Reducing sodium intake by about 1,000 mg/day is associated with reduced risk of cardiovascular events. C

Notes: Grades – A: convincing association, B: probable association, C: suggestive association

Includes evidence statements and gradings from the Evidence Report (literature from years 2002–2009). Does not include evidence from

other sources, such as the 2003 edition of the dietary guidelines (in which individual studies were classified according to their design as

level I, II or III but overall grades for relationships were not derived), although these sources have been used to inform these Guidelines.

Grade C evidence statements showing no association and all Grade D statements can be found in Appendix E.

Cardiovascular disease

•   Blood pressure: Reducing sodium intake reduces both systolic and diastolic blood pressure, and the effect is

greater in those with hypertension than in those with normal blood pressure:724-727

• in adults with normal blood pressure, a reduction of 1,800 mg per day reduces systolic blood pressure by
  about 2 mmHg and diastolic blood pressure by about 1 mmHg (Grade A; Evidence Report, Section 13.1)


• in adults with hypertension, a reduction of 1,800 mg per day reduces systolic blood pressure by about
  5 mmHg and diastolic blood pressure by about 3 mmHg (Grade A; Evidence Report, Section 13.1)724-739


• There is evidence of a probable association between a diet low in sodium and a reduction in blood pressure
  in children up to 18 years of age (Grade B; Evidence Report, Section 13.2).726,739,740

The Dietary Guidelines for Americans, 2010 drew similar conclusions regarding the relationship between sodium

and blood pressure. They state ‘a strong body of evidence has documented that in adults, as sodium intake

decreases, so does blood pressure. A moderate body of evidence has documented that as sodium intake

decreases, so does blood pressure in children, from birth to 18 years of age’.^198 They also note that people with

hypertension, diabetes and chronic kidney disease are more sensitive to sodium than healthier younger people,

and that sensitivity to sodium increases with age.

•   Cardiovascular disease: Despite extensive research on the relationship between sodium and blood pressure,

few long-term studies have examined changes in sodium intake related to changes in cardiovascular morbidity

and mortality. Past studies have mainly included subjects with hypertension. The evidence suggests that

reducing sodium intake by about 1,000 mg/day is associated with reduced risk of cardiovascular events

(Grade C; Evidence Report, Section 13.4).725,741-746 The results are consistent with drug trials showing that

reductions in hypertension also lead to decreases in adverse cardiovascular outcomes.747,748

Cancer

Evidence of a probable association between consumption of salt and salt-preserved foods with gastric cancer was

found in the systematic review prepared as the background paper for the Joint WHO/FAO Expert Consultation

on diet, nutrition and prevention of chronic diseases.74 9 This association was described as convincing by the

WCRF report (see Appendix F).^43 The WCRF report also reported convincing evidence of an association between

processed meats (meat preserved by smoking, curing, salting or addition of chemical preservatives such as

nitrites) and increased risk of colorectal cancer (see Appendix F)^43 but it is unclear whether the factor responsible

is the salt, other components such as nitrites, or a combination of these factors.