Individual efforts to reduce salt intake in China, Japan, UK, USA: What did people achieve? the INTERMAP population study

Objective: Habitual high-salt intake raises blood pressure and risk of cardiovascular diseases. To prevent/control these risks, reduced salt diet (RSD) is recommended in many countries and some people report practicing it; however, little is known about actual achievement. This population-based study assessed level of 24-h dietary sodium intake of participants reporting RSD and others. Method: Participants were 4680 men and women ages 40-59 years randomly selected from 17 populations in People's Republic of China (PRC), Japan, UK and USA, for an observational study on diet and blood pressure (INTERMAP). Daily sodium intake was determined by two timed 24-h urine collections. Antihypertensive treatment status and RSD were ascertained by questionnaire. Results: Participants reporting RSD were few; 3.1% (Japan), 1.3% (PRC), 2.5% (UK), 7.2% (USA); 15.1, 7.9, 16.7 and 16.8% of people with treated hypertension. For those reporting RSD, 24-h urinary sodium excretion was significantly, but only modestly lower than for others, by 17.9 mmol/day (Japan), 56.7 (PRC) and 14.7 (USA), but higher by 10.5 in UK. Sodium intakes for participants reporting RSD remained higher than recommended; 181.0 mmol/day (Japan), 171.5 (PRC), 155.2 (UK) and 148.9 (USA). For these people, as for others, main sources of salt were processed foods in Japan, UK and USA; in PRC, salt added in preparation at home. Conclusion: Enhanced sustained efforts are needed to raise general awareness of the harmful effects of salt on health and the benefits of salt reduction. Population approaches are needed to reduce salt content of processed foods and restaurant meals.