Hypertension is a major risk factor for cardiovascular diseases which now account for more than 27 % of all deaths in Bangladesh [1]. The amount of dietary salt consumed is an important determinant of blood pressure levels and a modest reduction in salt has been found to have a significant and, from a population perspective, important effect on lowering blood pressure [2–5]. It has been estimated that decreasing population-level salt intake from the estimated global levels of 9-12 g/d [6] to the recommended level of 5 g/d [7] would result in significant reduction of blood pressure and would reduce the world wide stroke rate and cardiovascular disease rate by 23% and 17%, respectively [8, 9]. Achieving this reduction would project to prevent 2.5 million deaths worldwide each year [8, 9]. While sodium is essential to sustain human life, the recommended daily consumption for meeting physiological need is only 1.5 g (3.8 g salt) [10]. The WHO recommendation of 5 g salt/d reflects a pragmatic compromise between the beneficial and achievable in terms of reducing salt consumption [7].

No current definitive estimate of population salt consumption in Bangladesh exists. Of two reported studies, one involves pregnant women in the southeastern coastal area and showed urinary sodium excretion of 170 mmol/day (equivalent 9 g salt) [11]. The other study was of 10 expatriate Bangladeshi patients with renal disease living in East London and showed that the two daily major meals combined to contain 10 g of salt per day [12]. The latter study is useful for understanding that a lot of salt is added to the Bangladeshi meal.

The low lying coastal belt of Bangladesh is highly vulnerable to the effects of climate change. Sea levels are rising, storms and cyclones are occurring more frequently, and soil and water salinity are increasing [13]. It is estimated that 20 million people living in coastal Bangladesh are already facing increased exposure to diseases like hypertension by the increased salinity of the water supply [14, 15]. In coastal areas it is estimated that salt intake from drinking water can range from 1.2-16 g/day depending on the water source and the season [15]. Therefore, it is important that levels of salt consumption among adults in coastal areas are established and factors associated with high salt consumption are investigated.

Our study is the first to describe the level and correlates of salt consumption among adults in coastal Bangladesh. The mean salt consumption of this population was 6.7 g/d (or 115 mmol Na/d) is comparable to those reported in Australia [21], Finland [22], Ghana and West Africa [23] and lower than those reported in other developed countries [24] and in South East Asian countries [6]. Also, the level of salt consumption was less than that reported in a study of pregnant women in the coastal belt of Bangladesh [15]. However, 75% of the study population still consumed more than their biological need and 59% of the population consumed more than the WHO recommended 5 g/d of salt. Having this much of the population exceeding the recommended levels of salt consumption is very concerning given the alarming levels of hypertension present in Bangladeshi adults [25]. Although results from the study area may not be representative of the nation, it is applicable to the coastal area of Bangladesh where 20 million people live [14] and are likely to be exposed to high levels of environmental salinity due to climate change.

Area of residence was by far the strongest predictor of high salt consumption in our study with those in the coastal area consuming the most. This is the first study to indicate that even with areas in close proximity, living directly in coastal areas makes a difference in salt consumption. Globally there is a rising concern that climate change will critically affect the freshwater resources of the world [26]. In Bangladesh, a country bearing some of the worst effects of global climate change, the rivers and ground water in coastal area are threatened by increased salinity from the Bay of Bengal [15]. The coastal population relies heavily on rivers, ground water and ponds for washing, bathing, and drinking water which could result in increased exposure to sodium [27]. Saline intrusion in the groundwater could also affect the sodium content of foods produced, and, therefore, cause increased consumption of salt without people being aware that their intake is increasing. Researchers have reported that excess salinity can be toxic to plants leading to reduced plant yield and plant death [28]. Depending on the variety of plants, sodium can accumulate within different parts of the plant despite existence of good mechanism of excluding sodium within the plant system [28]. It is important to investigate both these indirect sources of salt consumption and the effects of increased salinity on the available food supply.

In our study housewives had significantly higher salt intake than people (males) in labour-intensive occupations. As the majority of the women we studied were housewives, we found that women tended to have higher salt intake then men. The average salt intake of females (7 g) is slightly less than those reported among pregnant women in one coastal location of Bangladesh [15]. However, in studies around the world researchers have shown that women tend to consume less salt than men [6, 29]. Researchers have explained that the higher salt consumption among men was due to higher food intake. The explanation for the sex difference in salt consumption in our study may well lie in the context. In our study the men were engaged in labour-intensive occupations whereas women were mostly housewives. As 24 h urinary excretion takes no account of electrolyte loss other than through the kidneys [18], it is possible that the salt intake of men engaged in labour-intensive activities in Bangladesh’s tropical climate may have been underestimated. Another caveat to the explanation could be that housewives had better access to discretionary salt during meal times and, therefore, consumed more. To understand the sex differential in salt consumption it may be important to give further consideration to the context in which salt is consumed.

There have been reports of a growing prevalence of hypertension in Bangladesh [30–32], a trend predicted to continue in coming years. According to a recent Bangladeshi national survey (2011), 19.4% of males and 31.9% of females above 35 years of age were hypertensive [33]. To complicate the scenario, saline intrusions due sea-level rise and other effects of climate change have put 20 million people in the coastal belt at health risk from environmental exposure to sodium [14, 34]. Many researchers have shown that reduction of population-level salt intake is a cost-effective public health strategy [35, 36]. However, despite the cost-effectiveness, only a few countries have made progress implementing such a public health strategy [36]. For Bangladesh, in the absence of national data on salt consumption, and with existing geographic variations in salt consumption, it is important to understand the different sources of dietary salt and the beliefs and practices around salt use for designing appropriate strategies for different communities. In view of the deleterious health consequences of high salt intake, special attention should be given to coastal areas prone to saline intrusion in food and water sources and areas where cheap raw salt is easily available [34, 37]. So far the literature on climate change and health points to the proliferation of infectious disease (diarrhea), vector born disease (malaria) and diseases and health conditions due to migration and loss of livelihood [13]. However, direct health impacts of increased environmental salinity have yet to be addressed adequately. In view of the rising impact of climate change and the large number of people who will be affected, the link between increased salinity and health warrants attention.

Although the levels of salt consumption in the study population are lower than in some countries, more than three-fourths of the study population consumed more than biologically needed, and half consumed greater than the 5 g of salt daily. As salt consumption is a risk factor for hypertension, it is important that major sources of salt consumption are identified. Interventions to raise awareness about the detrimental health effects of excessive salt use should be designed for coastal communities. Looking to the future, policies that help to reduce salt consumption should be formulated for Bangladesh with special attention to climate-change-vulnerable coastal populations.