Effect of sodium-reduced potassium-enriched salt substitutes on stomach cancer: the Salt Substitute and Stroke Study (SSaSS)

Background: There is an association between increased dietary sodium intake and the risk of stomach cancer. Lowering dietary sodium intake with sodium-reduced potassium-enriched salt substitutes may reduce this risk. To evaluate the effects of sodium-reduced potassium-enriched salt substitutes on the risk of stomach cancer and other types of cancer. Methods: The primary analyses of the Salt Substitute and Stroke Study (SSaSS) defined the effects of sodium-reduced potassium-enriched salt substitutes compared to regular salt on the risk of stroke. This post-hoc investigation explored effects on stomach and other cancers. SSaSS was an open-label, cluster randomised controlled trial done in 600 Chinese villages among 20,996 participants. Villages were assigned at random in a 1:1 ratio to receive sodium-reduced potassium-enriched salt substitutes or continue regular salt use. Fatal and hospitalised cancer events were identified through direct face-to-face follow-up and record linkage, with adjudication of fatal, but not non-fatal events. Results: During a mean follow-up of 4.7 years, there were 1040 cancer events (507 fatal, 533 non-fatal) recorded. There were 212 stomach cancers, 725 other cancers, and 103 cancers with an unknown primary site. There was a trend toward but not a significant effect of randomised treatment on total stomach cancer (rate ratio (RR) 0.77, 95% confidence interval (CI) 0.54 to 1.08). The RR for adjudicated fatal stomach cancer was 0.66 (95% CI 0.44 to 1.00) compared to 0.88 (95% CI 0.56 to 1.37) for unadjudicated non-fatal stomach cancer. There was no detectable effect on total cancer at any site (RR 0.94, 95% CI 0.81 to 1.08), adjudicated fatal cancer at any site (RR 0.85, 95% CI 0.69 to 1.05), or unadjudicated non-fatal cancer at any site (RR 1.04, 95% CI 0.88 to 1.23). Conclusions: There was no effect of sodium-reduced potassium-enriched salt substitutes on stomach cancer or other cancer types detected. Trends toward protection against fatal and non-fatal stomach cancer align with the observational epidemiology and warrant further investigation. Trial registration: This trial was registered in ClinicalTrials.gov as NCT02092090.