Higher intakes of dietary salt intake have been shown to increase blood pressure [1, 2] and may have possible role in increased risk of stroke [3, 4]. Elevated blood pressure plays a major role in the aetiology of cardiovascular disease .
A number of Australian studies have found that salt intake ranges between 6.4 g to 10 g per day [6–8], exceeding the recommended maximum amount of 6 g/day . Similarly, data from U.S. and U.K. shows that the population salt intake exceeds the recommended amount [10, 11].
Similar to other western diets [12–14], the food categories that contribute most to Australians’ salt consumption are processed foods including bread and cereal products (32%) followed by meat products and dishes (21%) . It is estimated that processed foods account for about 80% of salt in the Australian diet while discretionary salt contributes about 20% . In order to achieve its population intake target of 6 g salt per day, the UK Food Standards Agency proposed a salt reduction strategy which comprises both reduction of salt in major salt contributing food categories (such as bread and cereals) as well as discretionary salt intake (i.e. salt added to the food) [17, 18].
In Australia, ischaemic heart disease and cardiovascular disease were the two leading causes of death in 2010 . The prevalence of cardiovascular disease and coronary heart disease was higher among the Australians in the lowest socio-economic groups compared to those in the highest socio-economic groups [20, 21]. Higher proportions of individuals with lower levels of education were diagnosed with hypertension compared to those with higher levels of education .
Differences observed in dietary behaviours and diet quality are often attributed to socio-demographic factors such as age , gender , education [23–25] and income [24, 25]. Similarly, use of discretionary salt is also associated with socio-economic factors . Individuals from lower income households, those with lower levels of education , males  and younger adults  have higher levels of discretionary salt use.
Apart from financial cost  and environmental factors such as access to healthier diets , social cognitive factors such as knowledge , self-efficacy , attitudes and beliefs  are often among the reasons attributed for the variation in dietary quality among the different socio-economic groups. For example, individuals with higher levels of education [31, 34–37] and higher incomes [34, 38] have been shown to have higher levels of nutrition knowledge. Similarly, women [31, 39] and older people [35, 38] tend to demonstrate higher levels of nutrition knowledge. More specifically, knowledge about salt has been found to be higher among older people and those with higher levels of education .
Although socio-demographic factors such as age, gender, education and income are indicators of health inequalities, unless there is a major societal change , little can be done in the short term to address or change these factors. Therefore, identification of modifiable, mediating factors may provide more feasible opportunities for interventions to reduce the disparities between the various socio-demographic groups.
To our knowledge, no study has examined the role of salt knowledge and beliefs as possible mediators between socio-demographic factors and discretionary salt use.
Given the importance of consumer knowledge as a likely influence on salt consumption and its importance for salt reduction policy monitoring , there is a need to clarify the role of salt knowledge and beliefs in relation to salt usage behaviour within the population.
Therefore, the aims of this study were 1) to examine the relationships between socio-demographic factors, salt knowledge, salt taste beliefs and discretionary salt use; and, 2) to determine the possible mediating roles of salt knowledge and salt taste beliefs in the relationships between socio-demographic status and discretionary salt use in an Australian adult population.