Results of a new research published in the English Daily Mail suggests that high salt consumption doubles risk of heart failure. The news article is based on a study which is recently published in 2017 Europe Cardiology Society Congress by Finnish researchers.

Review of the study results

This study conducted as a prospective cohort study that analyses the association between salt consumption and heart failure. In the baseline of the study, data of 4630 randomly selected men and women, aged of 25 -64 years who participated in Finland National FINRISK Study conducted in 1979-2000 together with North Karelia Salt Study were analysed.

Included participants were asked to respond a questionnaire in order to evaluate their health condition in the beginning of the study and various biochemical samples including urine samples of 24 hours were collected, urine samples were analysed. Excretion of each 17.1 millimole sodium was considered as a marker of 10g dietary salt intake. Urinary sodium excretion is golden standard in estimation of dietary salt intake. Based on this estimation, salt intake of the participants was classified into quintlies

<6.76g/day - 6.77–8.80g/day - 8.81–10.95g/day - 10.96–13.73g/day - >13.73g/day

Participants were monitored for 12 years with respect to a potential heart failure risk and therefore, cause of death, hospital and medication records of these individuals were also monitored regularly. 121 individuals in total developed heart failure in the end of 12 years.

Potential contribution of age, gender, study year, systolic blood pressure, cholesterol levels and body mass index as confounding factors for this risk was adjusted while analysing the association between dietary salt intake and the risk of heart failure. The frequency of heart failure (%) and developing heart failure (HR) in the groups consuming higher amounts of salt when compared with the individuals with the lowest salt intake (<6.76g).

• 13% with individuals consuming 6.77-8.80g salt/ day (hazard ratio (HR) 1.13)
• 45% with individuals consuming 8.81-10.95g salt/ day (hazard ratio (HR) 1.45)
• 56% with individuals consuming 10.96-13.73g salt/ day (hazard ratio (HR) 1.56)
• 75% with individuals consuming more than 13.73g salt /day (HR 1.75)

These results were presented as an abstract in congress, safety range for hazard ratios (HR) were not reported but risk increase in parallel with salt consumption is significant (p= 0.009).

Resource of the study: Jousilahti et al., (2017) Salt intake and the risk of heart failure. Presentation shared in the Europe Cardiology Society Congress on 27 August 2017.

How should study results be interpreted?

News article is based on the abstract of the study prepared for the conference and the press release: Results of the study have not been published in a peer-reviewed journal. Therefore, it is not possible to evaluate the reliability of the study as characteristics of the individuals included in the study and study methods are not known. Likewise, it is also not possible to generalize the study findings for the entire population.

The questionnaire aimed at determining health condition of the individuals was applied only in the beginning of the study: Life style and diet patterns of individuals may change substantially over time. Salt intake may have been increased or decreased over the study period of 12 years.

In addition to salt intake, there may be other factors that affected the risk of developing heart failure but not included in the statistical analyses: Certain parameters such as age, gender and body mass index were included in the study; however, factors such as physical activity, life style and diet patterns other than salt and socio-economic level can also affect the results. As is the case with all observation studies, it is not possible to say that total risk arose due to salt intake.

Information is required about the cohort properties: It is known that both men and women were included in the study, but their population is not known as limited information is given in the abstract of the study. Therefore, increased risk may have arisen only for men or only for elderly individuals, but it is not known.

Scientific facts:

• World Health Organization (WHO) recommends limitation of salt intake with 5g/day for adults. WHO reports that excessive salt intake is a common problem all over the world (9-12 g/day on average- two times higher than the recommended maximum level) and that excessive salt intake causes a series of diseases such as hypertension and stroke. It is also reported that reducing the salt intake is one of the cheapest and the most effective methods that can be implemented to prevent many health issues all over the world.

• There are also different national recommendations about salt intake. UK Scientific Advisory Committee on Nutrition (SACN) recommends limitation of salt intake with 6g/day for adults in parallel with the achievable targets.

References:
1.https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/338782/SACN_Salt_and_Health_report.pdf
2. http://www.who.int/mediacentre/factsheets/fs393/en/