The research, led by Nancy Cook from Harvard Medical School and published in the British Medical Journal, looks set to increase pressure on the food industry to reduce salt content in a wide range of foods. Numerous scientists are convinced that high salt intake is responsible for increasing blood pressure (hypertension), a major risk factor for cardiovascular disease (CVD) and the cause of almost 50 per cent of deaths in Europe. CVD is reported to cost the EU economy an estimated € 169bn ($202bn) per year. However, opponents to salt reduction have often stated that the link between salt intake and cardiovascular disease is not supported by sufficient evidence. Indeed, the authors note that high blood pressure is not a cardiovascular event and that studies showing an effect of sodium reduction on subsequent levels of cardiovascular disease in the population have been limited and inconclusive. "Despite its relatively small size as a trial of clinical outcomes, [out trial] provides the strongest evidence to date that lowering sodium intake, even among those without hypertension, reduced the risk of future cardiovascular disease," wrote Cook. The study included over 3,000 participants aged between 30 and 54 with high-normal blood pressure (pre-hypertension) who took part in the first and second Trial of Hypertension Prevention (TOHP). The interventions, which included sodium reduction, weight loss, and stress management lasted for 18 months (TOHP1, 744 subjects) or three to four years (TOHP2, 2382 subjects) and then followed for up to ten years after the end of the trial. In both trials participants reduced their sodium intake by approximately 25 to 35 per cent alongside a control group who didn't cut back on their salt intake. The researchers found that participants who had cut back on salt during the trials tended to stick to a lower salt diet compared to those who had been in the control group. In total the researchers obtained information from 2415 (77 per cent) participants, 200 of whom had reported some sort of cardiovascular problem (myocardial infarction, stroke, cardiovascular death). The results showed these pre-hypertensive individuals were 25 per cent less likely to develop cardiovascular problems over the course of the 10-15 years post-trial, with a 20 per cent lower mortality rate. This risk reduction was evident from both trials. "Our study provides unique evidence that sodium reduction might prevent cardiovascular disease and should dispel ay residual concern that sodium reduction might be harmful," said the authors. "The observed reduction in cardiovascular risk associated with this sodium decrease was substantial and provides strong support for population-wide reduction in dietary sodium intake to prevent cardiovascular disease," they concluded. In the UK, Ireland and the USA, over 80 per cent of salt intake comes from processed food, with 20 per cent of salt intake coming from meat and meat products, and about 35 per cent from cereal and cereal products. Prof. Graham MacGregor chair of both the newly formed World Action on Salt and Health (WASH) and Consensus Action on Salt and Health (CASH) welcomed the research. Both WASH and CASH have been active in pressuring food companies into reducing dietary salt intake in order to lower blood pressure. "This is a very important study because for the first time it shows that reducing salt intake does reduce the number of people suffering and dying from strokes and heart attacks, the biggest causes of death and disability in the UK," said Professor MacGregor. "Previous studies have predicted that reducing salt intake by 6 g/day will reduce the number of heart attack and strokes by approximately 70,000 events (35,000 deaths) a year in the UK alone, and this new research confirms these results." "With the accumulating evidence now available to us, and the fact that the majority of a person's salt intake comes from processed foods, every manufacturer now needs to act immediately to reduce the salt added to their foods," he added. The Salt Manufacturers Association is quoted by the BBC as saying the evidence did not prove that salt reduction would have any significant health benefits for the general population, but the association did concede that individuals with hypertension might be advised to restrict their salt intake. Source: British Medical Journal Published on-line ahead of print, doi: 10.1136/bmj.39147.604896.55 "Long term effects of dietary sodium reduction on cardiovascular disease outcomes: observational follow-up of the trials of hypertension prevention (TOHP)" Authors: N.R. Cook, J.A. Cutler, E. Obarzanek, J.E. Buring, K.M. Rexrode, S.K. Kumanyika, L.J. Appel, P.K. Whelton et al.
