Sanguine about salt reduction

Salt has been much in the media these last few months and mostly for the wrong reasons. Poor-quality, underpowered research has been misinterpreted and afforded undue attention by media outlets looking for a story. It is refreshing to see this issue of the journal reporting a new aspect of the salt story that is worthy of the attention – new plans for objectively tracking commitments to improve the composition of the global food supply. This proposal for systematic monitoring of progress with efforts to reduce salt in processed foods will be a key step in delivering upon the enormous potential of salt reduction programmes. For the first time, industry and governments around the world will be held to account by objective, quantitative measures of progress. While the true standardization of data collection across countries will doubtless be difficult to achieve, the pragmatic approach taken should add substantially to the public health armamentarium. For most of human evolution, man existed on a diet very different to that consumed now. Food contained just traces of sodium and only with the discovery that salt could preserve food did salt consumption levels start to rise. Now, some 6000 years on, average salt intake in most populations is much greater than is required to support normal physiology. With processed and fast foods now so widespread, it’s very hard to find a population that illustrates what can be achieved with consumption of a diet congruent with physiological needs. A good historical example is the Yanomamo Indians of the Amazon basin. When first studied by Western society in the 1950s, the Yanomamo were still consuming an unacculturated diet – low in fat and supplying just a fraction of a gram of salt each day. A striking consequence of the Yanomamo lifestyle was that blood pressure in old age was the same as in adolescence – an observation substantively attributable to lifetime consumption of sodium at normal physiological levels. Having the right concept of ‘normal’ is key to understanding the potential offered by salt reduction. Jointly, the anthropological, physiological, and epidemiological evidence suggests that ‘normal’ salt intake for most of human evolution was a gram or less a day. Correspondingly, for blood pressure, the consensus is now that normal adult systolic blood pressure is not ‘100mmHg plus age’, but about 100mmHg throughout the lifecourse. Maximum recommended daily salt consumption levels of 5–6 g represent a pragmatic compromise between the current consumption levels of most countries and achievable short-term targets, not a target for normalization of consumption. Likewise, being ‘non-hypertensive’ in old age is much better than being ‘hypertensive’, but having a blood pressure well below the 140mmHg threshold will confer a substantial further survival advantage. The downside of re-defining normal in this way is that it means that almost the entire global population is eating more salt than required and has a blood pressure above the optimum – with some adverse consequence for vascular risk in most. Defining normal systolic blood pressure as about 100mmHg is also the reason why blood pressure is the greatest cause of premature death and disability in the world – small increments in risks for huge numbers producing an enormous total disease burden. The upside of this equation is the potential for prevention – almost the entire global population stands to gain from a reduced salt intake and a lower blood pressure. And the potential benefits from population-wide programmes targeting these exposures are therefore enormous. While the reductions in risk for most individuals will be fairly small, the accumulation of these small reductions across the entire community translates into very large numbers of events that could be averted. Furthermore, because centrally implemented programmes targeting salt in the food supply require